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How reliable are ‘valid and reliable’ pain scores in the pediatric clinical setting?
Practice Points
Terri Voepel-Lewis* The clinical goals of diagnosing, intervening and evaluating pain treatments demand a practical
interpretation of pain scores based on an understanding of what pain scores indicate as clinically significant pain or the need for treatment, and what change in scores reflects sufficient pain relief. The large range of children’s scores associated with mild, moderate and severe pain suggest that the pain
score meaning differs substantially between individual children. There is a wide range of scores that children identify with treatment thresholds that differ substantially
from parents’ and nurses’ thresholds. Children’s perceptions of pain relief or worsening pain do not always correspond to changes in their pain
scores. Age, emotion and sex may influence the meaning that children attach to pain scores. Evidence suggests an individualized approach to interpreting and using pain scores in children that
includes: – Consideration of the clinical situation and factors, including social–emotional contexts that may influence the child’s self-report; – Evaluation of the medical condition and potential source(s) of pain; – Assessment of physiologic signs and symptoms; – Attention to behavioral signs and their interpretation given parents’ or others’ input; – Consideration of the functional needs and goals of the patient.
SUMMARY Over the past decade, growing clinician skepticism and inconsistent use of self-report pain scales have raised important questions regarding the clinical meaning and interpretation of pain scores. The appropriate use of pain scores at the bedside requires an understanding of what they may mean to the child who is providing them. This article summarizes the evidence regarding pain score meaning, showing that despite the established psychometric properties of pain scales, pain score numbers mean different things to different children, complicating the clinical interpretation. The evidence suggests that it is inappropriate to use standardized pain score thresholds for treatment or evaluation, and suggests an individualized approach to the interpretation and use of pain scores is needed. *Department of Anesthesiology, Section of Pediatrics, Room 4917 CS Mott Children’s Hospital, University of Michigan, Box 4245, 1540 E Hospital Drive, Ann Arbor, MI 48109 4245, USA; Tel.: +1 734 936 0747; Fax: +1 734 763 6651; [email protected]
10.2217/PMT.13.38 © 2013 Future Medicine Ltd
Pain Manage. (2013) 3(5), 343–350
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SPECIAL REPORT Voepel-Lewis The use of valid and reliable assessment tools is considered to be necessary to promote effective pain management, assess the effectiveness of interventions and quality of care, and to demonstrate institutional adherence to nationally accepted pain standards [1,2,101]. Such necessities propelled the widespread development and testing of instruments to assess pain in children over the past several decades, yielding multiple valid and reliable tools that are now in use across clinical settings. Those tools, meant to elicit selfreport, remain the recommended approach for assessing pain in children who are capable [3]. However, more than a decade of mandated pain assessment has led to clinician skepticism and inconsistent use of these instruments, and has raised important questions regarding the clinical meaning and interpretation of scores derived from them [4]. Clinician concerns have probably resulted, in part, from a general lack of evidence to guide clinical interpretation and the use of pain scores. Several investigators have, therefore, called for more data regarding interpretation [5–8], while others have called for a broader perspective on pain assessment with less emphasis on simplistic pain scores [9,10]. The appropriate use of selfreported pain scores at the bedside requires a good understanding of what they may mean to the child who is providing them. This article is meant to summarize the evidence regarding pain score meaning in an attempt to answer to the question, “How reliable are ‘valid and reliable’ pain scores in the pediatric clinical setting?” To answer this question, we first must consider the concepts of validity and reliability.
we cannot assume that one child’s valid score of 10/10 reflects more intense pain compared with another’s score of 7/10, since perceptions of anchors and intensity may differ [8]. In order for a self-report pain scale to yield a valid representation of a child’s personal pain experience or intensity, the child must be able to grasp how different points on the scale relate to one another (e.g., 5 > 2 > 1). Furthermore, a child’s valid pain score should be higher when a pain stimulus is greater (e.g., after surgery compared with before) and lower when the stimulus (or perception) has been removed (e.g., after analgesia), demonstrating what is known as construct validity.
Validity & reliability defined
Clinical meaning or interpretation of pain scores These psychometric properties of validity and reliability have been supported for several self-report tools in children, leading to age-based recommendations for their use in clinical trials [6]. Whereas the application and interpretation of pain scores in the research setting is straightforward (i.e., how do scores statistically compare between groups?), in the clinical setting, this is much more complex. The goals of diagnosing, intervening and evaluating treatment demand a more practical interpretation of pain scores based on an understanding of what pain scores indicate clinically significant pain or the need for treatment, and what change in scores reflects sufficient pain relief. Furthermore,
Validity
Validity, in the scientific sense, implies the extent to which an instrument measures what it is intended to measure. In the case of self-reported pain scales (e.g., Numerical rating [NRS], color analog [CAS], visual analog [VAS] or various faces pain scales [FPS]), the intent is to measure pain intensity or degree of pain experienced. Since pain is a personal experience, it could be argued that all self-reported pain scales possess face validity since they yield the individual’s personal score that reflects their perceived level of pain relative to scores they think represent higher or lower levels of pain. Thus, a valid self-reported pain score reflects the individual’s perceived pain intensity. As von Baeyer has emphasized,
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Reliability
Reliability on the other hand, refers to the consistency of a measure – that is, whether the instrument yields same or similar numbers under similar circumstances. For a pain scale to be reliable, then, it must yield the same (or very similar) score for the same child for the same circumstance or degree of injury, thus reflecting ‘test–retest’ reliability. When two different and valid instruments with the same scaling are used to measure the degree of pain from a stimulus, they should yield consistent scores, reflecting intermethod reliability. Lastly, the degree to which pain scores are consistent for the same circumstance between individuals would represent inter-rater reliability. However, since self-reported scores reflect personal perceptions of pain intensity, with each child having differing notions of what the least and worst pain anchors mean, their inter-rater reliability is irrelevant.
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How reliable are ‘valid & reliable’ pain scores in the pediatric clinical setting? the use of self-reported scores requires inter pretation and judgment in consideration of the child’s medical condition and possible sources of pain, and within the dynamic and complex social–environmental context [7,9,11,12]. Up until recently, data regarding pain score ‘meaning’ has been lacking, leaving interpretation largely in the hands of clinicians. Studies examining the practical characteristics of pain scales have compared children’s pain scores to their perceptions of pain severity (i.e., mild, moderate or severe), their perceived need for analgesia and satisfaction with treatment, and have related changes in scores to children’s perceptions of pain relief (i.e., feeling better). These data provide key insights into the usefulness of pain scores at the bedside. Perceived pain severity
Associations between pain scores and perceived pain severity have been demonstrated in a host of studies in adult populations, yet relatively few have addressed this relationship in children. Studies that have done so have identified average or median scores that children associate with and that are significantly different to the qualitative descriptions of mild, moderate and severe pain (Table 1) [13–16]. Despite the statistical differences in pain scores between descriptors, it is important, clinically, to note the large range of children’s scores associated with, and their overlap across, categories, suggesting that the meaning of pain scores can differ quite substantially between individual children. For instance, in the Gauthier et al. study, while a majority of children associated the same Bieri FPS score of
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‘3’ with moderate pain, a large number related this score to ‘mild’ pain, and at least one in their small sample, with ‘severe’ [14]. Similar overlaps were found for scores rated using the CAS [15] or NRS [13]. So, while researchers can comfortably use these median pain scores to represent mild, moderate or severe pain for populationbased research, clinicians may have much more difficulty drawing conclusions from individual pain scores at the individual bedside. Perceived treatment threshold
Other data have demonstrated average or median pain scores associated with children’s perceived need for treatment. These studies suggest that Bieri FPS scores greater than 2 or 3, or selfreported NRS scores equivalent to 4 or higher out of 10 are most likely to be associated with children’s perceived need for treatment (Table 2) [14,17,18]. Again, despite statistically significant differences between scores associated with the need for medicine and no need, the wide range of scores associated with need for medicine (e.g., range from 0 to 10, out of 10) demonstrates remarkable differences between the perceptions of individual children. Indeed, Voepel-Lewis et al. demonstrated that had the cutoff point of ‘4’ been applied to treat children in their sample, 42% would have been overtreated based on the child’s stated preference [18]. Although clinical guidelines have suggested that all moderate-to-severe pain should be treated, the data by Gauthier et al. demonstrate variable preferences in children [14]. For instance, 48% of their sample identified a treatment threshold that was within 1 point (above or
Table 1. Summary of evidence regarding pain scores children associate with clinically meaningful qualitative descriptors: perceived pain severity. Study (year) Gauthier et al. (1998) McConahay et al. (2006) Bailey et al. (2010) Page et al. (2012)†
Sample 48 postoperative children (6–16 years of age) 169 children in the emergency department (5–16 years of age) 202 children in the emergency department (8–17 years of age) 83 postoperative children (8–18 years of age)
Tool (range) FPS (0–6) CAS (0–10 cm)
Qualitative descriptors and average scores Mild pain
Moderate
Severe pain
Mean ± SD: 2.2 ± 1 (range: 1–5) Median: 3.5 (95% CI: 2–4.5; range: 0.5–6.0)
Mean ± SD: 3.2 ± 0.9 (range: 1–6) Median: 6.0 (95% CI: 5–7; range: 2–10)
Mean ± SD: 4.8 ± 0.9 (range: 2–6) Median: 8.5 (95% CI: 7–10; range: 3–10)
Ref. [14] [15]
VNS (0–10)
Median: 3 (interquartile Median: 6 (interquartile Median: 8 (interquartile range: 2–4) range: 4–7) range: 6–9)
[13]
NRS (0–10)
Median: 2.25 (interquartile range: 2–3; range: 1–7)
[16]
Median: 5 (interquartile Median: 7 (interquartile range: 3–6; range: 3–8) range: 5.5–8.5; range: 3–10)
Values approximated from data presented in figures as absolute numbers were not presented. CAS: Color analog scale; FPS: Various faces pain scale; NRS: Numerical rating scale; SD: Standard deviation; VNS: Verbal numeric scale. †
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SPECIAL REPORT Voepel-Lewis Table 2. Summary of evidence regarding pain scores children associate with clinically meaningful qualitative descriptors: perceived need for medicine (i.e., treatment threshold). Study (year) Gauthier et al. (1998) Demyttenaere et al. (2001) Voepel-Lewis et al. (2011)
Sample
Tool (range)
63 postoperative children FPS (0–6) (6–16 years of age) 25 postoperative children FPS (0–6) (6–16 years of age) 113 postoperative children NRS (0–10) (7–16 years of age)
Qualitative descriptors and average scores
Ref.
No need for treatment
Need medicine
NR
Mean ± SD: 3.2 ± 1.8 (range: 0–6)
[14]
NR
Mean ± SD: 2.33 ± 0.99† (range: 0–4.5) Median: 6.5; (interquartile range: 5–8; range: 0–10)
[17]
Median: 3 (interquartile range: 2–5; range: 0–10)
[18]
†
Average thresholds ranged from 1.85 ± 0.84 on postoperative day 3 to 2.54 ± 1.09 on day 2, although the means on different days were not significantly different. FPS: Various faces pain scale; NR: Not reported; NRS: Numerical rating scale; SD: Standard deviation.
below) of the score they associated with moderate severity, while a third stated a threshold that they associated only with mild pain. Although not reported, their data imply that for the remaining 23%, the preferred treatment threshold was in the perceived severe pain range. Reasons for children’s stated preferences have not yet been explored, but may be enlightening given the multiple developmental, psychological and environmental factors that may influence children’s desire (or not) for treatment. Perceived pain relief differences
Given the difficulties interpreting individual pain scores, several studies have further attempted to define ‘minimal clinically significant differences’ in pain scores for children – that is, what pain score change is associated with the child’s perception of pain relief (i.e., less pain). These studies, overall, suggest that a decrease of 1 point on 0–10 point scales or 10 on 0–100 point scales reflects clinically significant pain relief (Table 3) [13,18–21]. Again, while these changes in scores have been shown to be statistically significantly different and very useful for the researcher who is comparing treatment groups, the bedside practitioner may be presented with certain challenges when interpreting pain score differences. Substantial overlaps between scores assigned to perceptions of ‘feel better’ and ‘feel worse’, together with findings that up to 25% of scores change in the opposite direction of the child’s perceived pain relief suggest that an individual pain score change may not always reflect the child’s p erceived treatment outcome [18]. Trustworthiness of children’s self-reported pain scores The noted discrepancies in pain score data above suggest that individual pain scores may sometimes lack, or seem to lack, ‘credibility’ or
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‘trustworthiness’. These notions of reliability may be more consequential in the clinical setting, where the perceptions of care providers and parents are very likely to sway treatment decisions, and may differ substantially from those of children. Indeed, data from Demyttenaere et al. showed that parents’ and nurses’ treatment thresholds (i.e., Bieri FPS score at which they believed the child needed treatment) agreed with children in only 24 and 20% of cases, respectively [17]. Parents’ thresholds tended to be higher than their children more often than nurses’ thresholds (56 vs 36% of cases), which, in turn, were more often lower than the child’s (32 vs 24% for parents). These data suggest that whether or when parents or nurses use their own preferred pain score thresholds to make treatment decisions, they would more often under- or over-treat the child (that is, compared with the child’s stated preferences). Recent data from an adult acute care setting similarly demonstrated discrepant pain score interpretation, with nurses generally associating lower scores with unbearable, and therefore treatable, pain compared with patients [22]. Despite ongoing suggestions by some that self-report is the ‘correct’ assessment, these and other scoring discrepancies between patients and their caregivers emphasize the difficulties in discerning meaning from discrete pain scores. It is, therefore, important to understand some of the factors contributing to potential ‘errors’, exaggerations or biases in children’s scoring so that the misuse of pain scores based on incorrect assumptions can be avoided. Pain scale incongruities
Although studies show very good correlations between scores provided concurrently using different self-report pain scales, there are also distinct differences, suggesting that variable scale interpretation may contribute to scoring bias. For
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How reliable are ‘valid & reliable’ pain scores in the pediatric clinical setting? instance, some data suggest comparable NRS and FPS or VAS scores when provided by children after surgery [4,23], while others show that nearly a third of children score 2 or more points higher with the NRS (vs the FPS) for postoperative or hypothetical pain [16,24]. Similar disagreements were found when children scored their pain in the emergency room using the NRS, FPS, VAS and CAS [13]. Score differences have been explained, in part, by the possible influence of descriptive anchors (e.g., ‘worst possible’ vs ‘most’ pain) [13,25]. Additionally, while some scales only have two anchors (i.e., the zero and highest points), others have descriptors (i.e., numbers or faces) throughout the scale. The salience and meaning of these anchors and descriptors may lead to differences in the child’s scoring behaviors based on differing interpretations. Age influence
Interpretation of anchors and scores may be influenced by the age of the child given their cognitive
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and experiential differences. Although separate studies that included children aged 7 or 8 to 17 years found no age effect on the noted discrepancies between concurrent scores on the NRS and FPS-revised [16,25], other data suggest that higher pain scores may be a function of increasing age [4]. In younger samples, the influence of age has been shown to be much greater. For instance, in one study, children aged 3–6 years scored standardized hypothetical vignettes wherein pain levels had been predefined (based on population means) as none, mild, moderate or severe pain situations [26]. A total of 40–60% of children scored pain in a range outside the predefined level, with 3- and 4-year olds making significantly more scoring ‘errors’ compared with the older age groups. Interestingly, age, and not cognitive test results (seriation, classification, language or cognitive ability), was the only predictor for scoring errors, suggesting that differing perceptions of pain and pain situations may be based, in part, on experience.
Table 3. Summary of evidence regarding pain scores children associate with clinically meaningful qualitative descriptors: perceived pain relief (i.e., change in score from baseline)†. Study (year)
Bulloch et al. (2002)
Powell et al. (2001) Kelly (2001)
Bailey et al. (2010)‡
Sample
121 children in the emergency department (5–16 years of age)
73 children in emergency department (8–15 years of age) 73 children (≥8 years of age) and 152 adults in the emergency department 202 patients in the emergency department (8–17 years of age)
Voepel-Lewis 119 children in the et al. (2011) postoperative setting (7–16 years of age)
Tool (range)
Qualitative descriptors and average change in scores A lot better (much less)
CAS (0–10 cm)
A little better Same (less)
A little worse
A lot worse
Median: -4 (interquartile range: 2–5) Median: -3.8; (95% CI: -3.1 to -4.5) FPS (0–10) Median: -2 (interquartile range: 2–3) VAS Median: 13 (0–100 mm) (interquartile range: 7–26) VAS Median: (0–100 mm) 23 (95% CI: 20–34)
Median: -2 (interquartile range: 1–3) Median: -1.7 (95% CI: -1.1 to -2.3) Median: -1 (interquartile range: 1–2) Median: 9 (interquartile range: 15–19) NR
Median: 0 NR (interquartile range: 0–1)
NR
Median: 0 (interquartile range: 0–1) Median: 0 (interquartile range: -3 to 4) Median: 0 (95% CI: -2 to 1)
NR
NR
Median: 8 (interquartile range: 0 to -14) NR
Median: 13 (interquartile range: -11 to -13) NR
NRS (0–10)
Median: -1 (interquartile range: -2 to 0; range: -3 to 2) Median: -1 (95% CI: -0.5 to -1.5)
Median: 0 (interquartile range: -0.25 to 0; range: -0.5 to 0) Median: -0.9 (95% CI: -0.5 to 0.2)
Median: 1 (interquartile range: 0–1.5; range: 1–3)
Median: 2 (interquartile range: 2–3; range: 1–4)
NRS (0–10)
Median: -2.5 (interquartile range: -5 to -1; range: -9 to 2) Median: -3 (95% CI: -2 to -4)
Ref.
Median: 1.2 Median: 3.8 (95% CI: 1.8–2) (95% CI: 1.2–5.7)
[20]
[19]
[21]
[13]
[18]
Data presented verbatim, although it is assumed that ‘less pain’ or ‘better’ implies a decrease in pain score. Values approximated from data presented in figures. CAS: Color analog scale; FPS: Various faces pain scale; NR: Not reported; NRS: Numeric rating scale; VAS: Visual analog scale. † ‡
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SPECIAL REPORT Voepel-Lewis Another study re-examined these and other data for potential anchor (i.e., always choosing the top or bottom score) or sequence (i.e., choosing the next or adjacent face in an ascending or descending manner) biases [27]. Data showed that younger children were more likely to provide biased scores compared with older children (63, 51 and 42% of 3-, 4- and 5-year olds, respectively). The investigators suggested that such scoring tendencies may represent a strategy to respond to difficult or complex questions that young children do not understand. Such lack of understanding in young children was, in fact, demonstrated in a more recent study where children were asked to score hypothetical pain vignettes using either the FPS-revised or a simplified scale eliciting reports of no pain, mild, moderate and severe pain [28]. The 5-year olds in this study showed no differences in their discrimination between the zero-, medium- and high-pain vignettes when using the differing scales. However, use of the simplified tool allowed the 3-year olds to better discriminate the zero- and mediumpain vignettes and the 4-year olds to better discriminate the zero-pain vignettes. These data demonstrate the difficulties that young children may have when using the usual FPS. Affect & sex influences
Pain score meaning may also reflect emotional and social influences. For instance, Chambers and Craig showed how children’s pain scores are biased upward or downward in response to emotional context (e.g., winning a race) or affectively laden anchors (smiley vs neutral faces) [29]. Preand post-operative pain ratings using various scales have been shown to be higher as a function of baseline state anxiety [4]. Furthermore, postoperative pain scores were found to strongly correlate with several measures of negative affect (i.e., how unpleasant, upset or afraid they felt at the time of assessment) [4,16]. These studies suggest that it may be difficult to discern pain intensity from other emotional states or feelings in the clinical setting [4,16]. Pain score meaning may also be influenced by sex. For instance, compared with boys, girls have scored immunization pain higher [24], associated lower pain scores with moderate-to-severe pain [14] and expressed satisfaction with analgesia at higher scores [18]. Additionally, boys who had higher masculinity ratings were found to be less willing to express pain compared with girls in experimental settings [30,31]. No differences have
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been found between the pain scores that boys and girls associate with treatment thresholds [14,17,18]. Conclusion & future perspective This article has highlighted some of the ongoing quandaries that plague clinicians when faced with interpreting and responding to children’s pain scores. Despite data supporting the psycho metric validity and reliability of self-report pain scales, evidence demonstrates wide variability in the clinical meaning that children attach to pain scores. Such findings suggest that it is inappropriate to use or establish standardized pain score thresholds for treatment or evaluation. In fact, doing so may jeopardize effective and safe pain management [32–35]. Instead, an individualized approach to the interpretation and use of pain scores is warranted to promote better treatment decisions [36]. Such an approach involves consideration of the clinical situation at hand and factors, including social–emotional contexts, that may influence the child’s self-report [12]. Critical analysis of the child’s self-report within context includes an evaluation of the medical condition and potential source(s) of pain (e.g., postoperative pain), physiologic signs and symptoms, behavioral observation and interpretation of behaviors with parents’ or others’ input, and consideration of the functional needs and goals of the patient [11,12]. Schiavenato and Craig have suggested that such a broad assessment culminates in a clinical judgment or final evaluation that invariably guides the decision to intervene [9]. Re-evaluating pain scores, behaviors and other factors following the effects of interventions may provide the best data for interpreting and understanding the meaning of the individual child’s self-report in order to best guide ongoing treatment decisions. Over the past decade, a growing consensus has emerged that self-reported pain scores – even when derived from scales purported to be valid and reliable – are an oversimplistic and insufficient means by which to make clinical decisions [7,9–12,37–39]. Over the next few years, we will probably see less emphasis on pain scores, and development of new methods that will better inform analgesic decisions and evaluation. Several investigators have suggested that the preferred method of pain assessment in children should consider both self-report and a behavioral or observer component [8,11]. Others have suggested incorporation of measures of physical functioning or pain impact, pain distress or,
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How reliable are ‘valid & reliable’ pain scores in the pediatric clinical setting? perhaps, acceptability of pain (e.g., ‘bearable’ vs ‘unbearable’) [22,37,40]. Such alternative methods need to be tried in the clinical setting and evaluated based on real outcomes that are important to the patient and clinician alike. To date, it remains unknown what the next best valid and reliable method of assessing children’s pain in the clinical setting will be. However, it will probably to diverge substantially from the simplistic pain intensity score. References
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Financial & competing interests disclosure The author has no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties. No writing assistance was utilized in the production of this manuscript. Highlights some of the important considerations for use and interpretation of self-reported pain scores in children.
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Simple pain rating scales hide complex idiosyncratic meanings. Pain 85(3), 457–463 (2000).
34 Taylor S, Voytovich AE, Kozol RA. Has the
40 Fraenkel L, Falzer P, Fried T et al. Measuring
pendulum swung too far in postoperative pain control? Am. J. Surg. 186(5), 472–475 (2003).
pain impact versus pain severity using a numeric rating scale. J. Gen. Intern. Med. 27(5), 555–560 (2012).
35 Vila H Jr, Smith RA, Augustyniak MJ et al.
The efficacy and safety of pain management before and after implementation of hospital-wide pain management standards: is patient safety compromised by treatment based solely on numerical pain ratings? Anesth. Analg. 101(2), 474–480 (2005). 36 Voepel-Lewis T. Pain assessment and decision
making: Have we missed the mark? Pediatric Pain Letter 13(1), 1–6 (2011).
Pain Manage. (2013) 3(5)
n
Suggests that pain impact is more important in determining adult patients’ need or desire for treatment than pain intensity scores.
Website 101 Health Care Association of New Jersey. Pain
management guideline. www.guideline.gov/content.aspx?id=9744 (Accessed 2 August 2013)
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How reliable are ‘valid and reliable’ pain scores in the pediatric clinical setting?
Practice Points
Terri Voepel-Lewis* The clinical goals of diagnosing, intervening and evaluating pain treatments demand a practical
interpretation of pain scores based on an understanding of what pain scores indicate as clinically significant pain or the need for treatment, and what change in scores reflects sufficient pain relief. The large range of children’s scores associated with mild, moderate and severe pain suggest that the pain
score meaning differs substantially between individual children. There is a wide range of scores that children identify with treatment thresholds that differ substantially
from parents’ and nurses’ thresholds. Children’s perceptions of pain relief or worsening pain do not always correspond to changes in their pain
scores. Age, emotion and sex may influence the meaning that children attach to pain scores. Evidence suggests an individualized approach to interpreting and using pain scores in children that
includes: – Consideration of the clinical situation and factors, including social–emotional contexts that may influence the child’s self-report; – Evaluation of the medical condition and potential source(s) of pain; – Assessment of physiologic signs and symptoms; – Attention to behavioral signs and their interpretation given parents’ or others’ input; – Consideration of the functional needs and goals of the patient.
SUMMARY Over the past decade, growing clinician skepticism and inconsistent use of self-report pain scales have raised important questions regarding the clinical meaning and interpretation of pain scores. The appropriate use of pain scores at the bedside requires an understanding of what they may mean to the child who is providing them. This article summarizes the evidence regarding pain score meaning, showing that despite the established psychometric properties of pain scales, pain score numbers mean different things to different children, complicating the clinical interpretation. The evidence suggests that it is inappropriate to use standardized pain score thresholds for treatment or evaluation, and suggests an individualized approach to the interpretation and use of pain scores is needed. *Department of Anesthesiology, Section of Pediatrics, Room 4917 CS Mott Children’s Hospital, University of Michigan, Box 4245, 1540 E Hospital Drive, Ann Arbor, MI 48109 4245, USA; Tel.: +1 734 936 0747; Fax: +1 734 763 6651; [email protected]
10.2217/PMT.13.38 © 2013 Future Medicine Ltd
Pain Manage. (2013) 3(5), 343–350
part of
ISSN 1758-1869
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SPECIAL REPORT Voepel-Lewis The use of valid and reliable assessment tools is considered to be necessary to promote effective pain management, assess the effectiveness of interventions and quality of care, and to demonstrate institutional adherence to nationally accepted pain standards [1,2,101]. Such necessities propelled the widespread development and testing of instruments to assess pain in children over the past several decades, yielding multiple valid and reliable tools that are now in use across clinical settings. Those tools, meant to elicit selfreport, remain the recommended approach for assessing pain in children who are capable [3]. However, more than a decade of mandated pain assessment has led to clinician skepticism and inconsistent use of these instruments, and has raised important questions regarding the clinical meaning and interpretation of scores derived from them [4]. Clinician concerns have probably resulted, in part, from a general lack of evidence to guide clinical interpretation and the use of pain scores. Several investigators have, therefore, called for more data regarding interpretation [5–8], while others have called for a broader perspective on pain assessment with less emphasis on simplistic pain scores [9,10]. The appropriate use of selfreported pain scores at the bedside requires a good understanding of what they may mean to the child who is providing them. This article is meant to summarize the evidence regarding pain score meaning in an attempt to answer to the question, “How reliable are ‘valid and reliable’ pain scores in the pediatric clinical setting?” To answer this question, we first must consider the concepts of validity and reliability.
we cannot assume that one child’s valid score of 10/10 reflects more intense pain compared with another’s score of 7/10, since perceptions of anchors and intensity may differ [8]. In order for a self-report pain scale to yield a valid representation of a child’s personal pain experience or intensity, the child must be able to grasp how different points on the scale relate to one another (e.g., 5 > 2 > 1). Furthermore, a child’s valid pain score should be higher when a pain stimulus is greater (e.g., after surgery compared with before) and lower when the stimulus (or perception) has been removed (e.g., after analgesia), demonstrating what is known as construct validity.
Validity & reliability defined
Clinical meaning or interpretation of pain scores These psychometric properties of validity and reliability have been supported for several self-report tools in children, leading to age-based recommendations for their use in clinical trials [6]. Whereas the application and interpretation of pain scores in the research setting is straightforward (i.e., how do scores statistically compare between groups?), in the clinical setting, this is much more complex. The goals of diagnosing, intervening and evaluating treatment demand a more practical interpretation of pain scores based on an understanding of what pain scores indicate clinically significant pain or the need for treatment, and what change in scores reflects sufficient pain relief. Furthermore,
Validity
Validity, in the scientific sense, implies the extent to which an instrument measures what it is intended to measure. In the case of self-reported pain scales (e.g., Numerical rating [NRS], color analog [CAS], visual analog [VAS] or various faces pain scales [FPS]), the intent is to measure pain intensity or degree of pain experienced. Since pain is a personal experience, it could be argued that all self-reported pain scales possess face validity since they yield the individual’s personal score that reflects their perceived level of pain relative to scores they think represent higher or lower levels of pain. Thus, a valid self-reported pain score reflects the individual’s perceived pain intensity. As von Baeyer has emphasized,
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Reliability
Reliability on the other hand, refers to the consistency of a measure – that is, whether the instrument yields same or similar numbers under similar circumstances. For a pain scale to be reliable, then, it must yield the same (or very similar) score for the same child for the same circumstance or degree of injury, thus reflecting ‘test–retest’ reliability. When two different and valid instruments with the same scaling are used to measure the degree of pain from a stimulus, they should yield consistent scores, reflecting intermethod reliability. Lastly, the degree to which pain scores are consistent for the same circumstance between individuals would represent inter-rater reliability. However, since self-reported scores reflect personal perceptions of pain intensity, with each child having differing notions of what the least and worst pain anchors mean, their inter-rater reliability is irrelevant.
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How reliable are ‘valid & reliable’ pain scores in the pediatric clinical setting? the use of self-reported scores requires inter pretation and judgment in consideration of the child’s medical condition and possible sources of pain, and within the dynamic and complex social–environmental context [7,9,11,12]. Up until recently, data regarding pain score ‘meaning’ has been lacking, leaving interpretation largely in the hands of clinicians. Studies examining the practical characteristics of pain scales have compared children’s pain scores to their perceptions of pain severity (i.e., mild, moderate or severe), their perceived need for analgesia and satisfaction with treatment, and have related changes in scores to children’s perceptions of pain relief (i.e., feeling better). These data provide key insights into the usefulness of pain scores at the bedside. Perceived pain severity
Associations between pain scores and perceived pain severity have been demonstrated in a host of studies in adult populations, yet relatively few have addressed this relationship in children. Studies that have done so have identified average or median scores that children associate with and that are significantly different to the qualitative descriptions of mild, moderate and severe pain (Table 1) [13–16]. Despite the statistical differences in pain scores between descriptors, it is important, clinically, to note the large range of children’s scores associated with, and their overlap across, categories, suggesting that the meaning of pain scores can differ quite substantially between individual children. For instance, in the Gauthier et al. study, while a majority of children associated the same Bieri FPS score of
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‘3’ with moderate pain, a large number related this score to ‘mild’ pain, and at least one in their small sample, with ‘severe’ [14]. Similar overlaps were found for scores rated using the CAS [15] or NRS [13]. So, while researchers can comfortably use these median pain scores to represent mild, moderate or severe pain for populationbased research, clinicians may have much more difficulty drawing conclusions from individual pain scores at the individual bedside. Perceived treatment threshold
Other data have demonstrated average or median pain scores associated with children’s perceived need for treatment. These studies suggest that Bieri FPS scores greater than 2 or 3, or selfreported NRS scores equivalent to 4 or higher out of 10 are most likely to be associated with children’s perceived need for treatment (Table 2) [14,17,18]. Again, despite statistically significant differences between scores associated with the need for medicine and no need, the wide range of scores associated with need for medicine (e.g., range from 0 to 10, out of 10) demonstrates remarkable differences between the perceptions of individual children. Indeed, Voepel-Lewis et al. demonstrated that had the cutoff point of ‘4’ been applied to treat children in their sample, 42% would have been overtreated based on the child’s stated preference [18]. Although clinical guidelines have suggested that all moderate-to-severe pain should be treated, the data by Gauthier et al. demonstrate variable preferences in children [14]. For instance, 48% of their sample identified a treatment threshold that was within 1 point (above or
Table 1. Summary of evidence regarding pain scores children associate with clinically meaningful qualitative descriptors: perceived pain severity. Study (year) Gauthier et al. (1998) McConahay et al. (2006) Bailey et al. (2010) Page et al. (2012)†
Sample 48 postoperative children (6–16 years of age) 169 children in the emergency department (5–16 years of age) 202 children in the emergency department (8–17 years of age) 83 postoperative children (8–18 years of age)
Tool (range) FPS (0–6) CAS (0–10 cm)
Qualitative descriptors and average scores Mild pain
Moderate
Severe pain
Mean ± SD: 2.2 ± 1 (range: 1–5) Median: 3.5 (95% CI: 2–4.5; range: 0.5–6.0)
Mean ± SD: 3.2 ± 0.9 (range: 1–6) Median: 6.0 (95% CI: 5–7; range: 2–10)
Mean ± SD: 4.8 ± 0.9 (range: 2–6) Median: 8.5 (95% CI: 7–10; range: 3–10)
Ref. [14] [15]
VNS (0–10)
Median: 3 (interquartile Median: 6 (interquartile Median: 8 (interquartile range: 2–4) range: 4–7) range: 6–9)
[13]
NRS (0–10)
Median: 2.25 (interquartile range: 2–3; range: 1–7)
[16]
Median: 5 (interquartile Median: 7 (interquartile range: 3–6; range: 3–8) range: 5.5–8.5; range: 3–10)
Values approximated from data presented in figures as absolute numbers were not presented. CAS: Color analog scale; FPS: Various faces pain scale; NRS: Numerical rating scale; SD: Standard deviation; VNS: Verbal numeric scale. †
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SPECIAL REPORT Voepel-Lewis Table 2. Summary of evidence regarding pain scores children associate with clinically meaningful qualitative descriptors: perceived need for medicine (i.e., treatment threshold). Study (year) Gauthier et al. (1998) Demyttenaere et al. (2001) Voepel-Lewis et al. (2011)
Sample
Tool (range)
63 postoperative children FPS (0–6) (6–16 years of age) 25 postoperative children FPS (0–6) (6–16 years of age) 113 postoperative children NRS (0–10) (7–16 years of age)
Qualitative descriptors and average scores
Ref.
No need for treatment
Need medicine
NR
Mean ± SD: 3.2 ± 1.8 (range: 0–6)
[14]
NR
Mean ± SD: 2.33 ± 0.99† (range: 0–4.5) Median: 6.5; (interquartile range: 5–8; range: 0–10)
[17]
Median: 3 (interquartile range: 2–5; range: 0–10)
[18]
†
Average thresholds ranged from 1.85 ± 0.84 on postoperative day 3 to 2.54 ± 1.09 on day 2, although the means on different days were not significantly different. FPS: Various faces pain scale; NR: Not reported; NRS: Numerical rating scale; SD: Standard deviation.
below) of the score they associated with moderate severity, while a third stated a threshold that they associated only with mild pain. Although not reported, their data imply that for the remaining 23%, the preferred treatment threshold was in the perceived severe pain range. Reasons for children’s stated preferences have not yet been explored, but may be enlightening given the multiple developmental, psychological and environmental factors that may influence children’s desire (or not) for treatment. Perceived pain relief differences
Given the difficulties interpreting individual pain scores, several studies have further attempted to define ‘minimal clinically significant differences’ in pain scores for children – that is, what pain score change is associated with the child’s perception of pain relief (i.e., less pain). These studies, overall, suggest that a decrease of 1 point on 0–10 point scales or 10 on 0–100 point scales reflects clinically significant pain relief (Table 3) [13,18–21]. Again, while these changes in scores have been shown to be statistically significantly different and very useful for the researcher who is comparing treatment groups, the bedside practitioner may be presented with certain challenges when interpreting pain score differences. Substantial overlaps between scores assigned to perceptions of ‘feel better’ and ‘feel worse’, together with findings that up to 25% of scores change in the opposite direction of the child’s perceived pain relief suggest that an individual pain score change may not always reflect the child’s p erceived treatment outcome [18]. Trustworthiness of children’s self-reported pain scores The noted discrepancies in pain score data above suggest that individual pain scores may sometimes lack, or seem to lack, ‘credibility’ or
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‘trustworthiness’. These notions of reliability may be more consequential in the clinical setting, where the perceptions of care providers and parents are very likely to sway treatment decisions, and may differ substantially from those of children. Indeed, data from Demyttenaere et al. showed that parents’ and nurses’ treatment thresholds (i.e., Bieri FPS score at which they believed the child needed treatment) agreed with children in only 24 and 20% of cases, respectively [17]. Parents’ thresholds tended to be higher than their children more often than nurses’ thresholds (56 vs 36% of cases), which, in turn, were more often lower than the child’s (32 vs 24% for parents). These data suggest that whether or when parents or nurses use their own preferred pain score thresholds to make treatment decisions, they would more often under- or over-treat the child (that is, compared with the child’s stated preferences). Recent data from an adult acute care setting similarly demonstrated discrepant pain score interpretation, with nurses generally associating lower scores with unbearable, and therefore treatable, pain compared with patients [22]. Despite ongoing suggestions by some that self-report is the ‘correct’ assessment, these and other scoring discrepancies between patients and their caregivers emphasize the difficulties in discerning meaning from discrete pain scores. It is, therefore, important to understand some of the factors contributing to potential ‘errors’, exaggerations or biases in children’s scoring so that the misuse of pain scores based on incorrect assumptions can be avoided. Pain scale incongruities
Although studies show very good correlations between scores provided concurrently using different self-report pain scales, there are also distinct differences, suggesting that variable scale interpretation may contribute to scoring bias. For
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How reliable are ‘valid & reliable’ pain scores in the pediatric clinical setting? instance, some data suggest comparable NRS and FPS or VAS scores when provided by children after surgery [4,23], while others show that nearly a third of children score 2 or more points higher with the NRS (vs the FPS) for postoperative or hypothetical pain [16,24]. Similar disagreements were found when children scored their pain in the emergency room using the NRS, FPS, VAS and CAS [13]. Score differences have been explained, in part, by the possible influence of descriptive anchors (e.g., ‘worst possible’ vs ‘most’ pain) [13,25]. Additionally, while some scales only have two anchors (i.e., the zero and highest points), others have descriptors (i.e., numbers or faces) throughout the scale. The salience and meaning of these anchors and descriptors may lead to differences in the child’s scoring behaviors based on differing interpretations. Age influence
Interpretation of anchors and scores may be influenced by the age of the child given their cognitive
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and experiential differences. Although separate studies that included children aged 7 or 8 to 17 years found no age effect on the noted discrepancies between concurrent scores on the NRS and FPS-revised [16,25], other data suggest that higher pain scores may be a function of increasing age [4]. In younger samples, the influence of age has been shown to be much greater. For instance, in one study, children aged 3–6 years scored standardized hypothetical vignettes wherein pain levels had been predefined (based on population means) as none, mild, moderate or severe pain situations [26]. A total of 40–60% of children scored pain in a range outside the predefined level, with 3- and 4-year olds making significantly more scoring ‘errors’ compared with the older age groups. Interestingly, age, and not cognitive test results (seriation, classification, language or cognitive ability), was the only predictor for scoring errors, suggesting that differing perceptions of pain and pain situations may be based, in part, on experience.
Table 3. Summary of evidence regarding pain scores children associate with clinically meaningful qualitative descriptors: perceived pain relief (i.e., change in score from baseline)†. Study (year)
Bulloch et al. (2002)
Powell et al. (2001) Kelly (2001)
Bailey et al. (2010)‡
Sample
121 children in the emergency department (5–16 years of age)
73 children in emergency department (8–15 years of age) 73 children (≥8 years of age) and 152 adults in the emergency department 202 patients in the emergency department (8–17 years of age)
Voepel-Lewis 119 children in the et al. (2011) postoperative setting (7–16 years of age)
Tool (range)
Qualitative descriptors and average change in scores A lot better (much less)
CAS (0–10 cm)
A little better Same (less)
A little worse
A lot worse
Median: -4 (interquartile range: 2–5) Median: -3.8; (95% CI: -3.1 to -4.5) FPS (0–10) Median: -2 (interquartile range: 2–3) VAS Median: 13 (0–100 mm) (interquartile range: 7–26) VAS Median: (0–100 mm) 23 (95% CI: 20–34)
Median: -2 (interquartile range: 1–3) Median: -1.7 (95% CI: -1.1 to -2.3) Median: -1 (interquartile range: 1–2) Median: 9 (interquartile range: 15–19) NR
Median: 0 NR (interquartile range: 0–1)
NR
Median: 0 (interquartile range: 0–1) Median: 0 (interquartile range: -3 to 4) Median: 0 (95% CI: -2 to 1)
NR
NR
Median: 8 (interquartile range: 0 to -14) NR
Median: 13 (interquartile range: -11 to -13) NR
NRS (0–10)
Median: -1 (interquartile range: -2 to 0; range: -3 to 2) Median: -1 (95% CI: -0.5 to -1.5)
Median: 0 (interquartile range: -0.25 to 0; range: -0.5 to 0) Median: -0.9 (95% CI: -0.5 to 0.2)
Median: 1 (interquartile range: 0–1.5; range: 1–3)
Median: 2 (interquartile range: 2–3; range: 1–4)
NRS (0–10)
Median: -2.5 (interquartile range: -5 to -1; range: -9 to 2) Median: -3 (95% CI: -2 to -4)
Ref.
Median: 1.2 Median: 3.8 (95% CI: 1.8–2) (95% CI: 1.2–5.7)
[20]
[19]
[21]
[13]
[18]
Data presented verbatim, although it is assumed that ‘less pain’ or ‘better’ implies a decrease in pain score. Values approximated from data presented in figures. CAS: Color analog scale; FPS: Various faces pain scale; NR: Not reported; NRS: Numeric rating scale; VAS: Visual analog scale. † ‡
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SPECIAL REPORT Voepel-Lewis Another study re-examined these and other data for potential anchor (i.e., always choosing the top or bottom score) or sequence (i.e., choosing the next or adjacent face in an ascending or descending manner) biases [27]. Data showed that younger children were more likely to provide biased scores compared with older children (63, 51 and 42% of 3-, 4- and 5-year olds, respectively). The investigators suggested that such scoring tendencies may represent a strategy to respond to difficult or complex questions that young children do not understand. Such lack of understanding in young children was, in fact, demonstrated in a more recent study where children were asked to score hypothetical pain vignettes using either the FPS-revised or a simplified scale eliciting reports of no pain, mild, moderate and severe pain [28]. The 5-year olds in this study showed no differences in their discrimination between the zero-, medium- and high-pain vignettes when using the differing scales. However, use of the simplified tool allowed the 3-year olds to better discriminate the zero- and mediumpain vignettes and the 4-year olds to better discriminate the zero-pain vignettes. These data demonstrate the difficulties that young children may have when using the usual FPS. Affect & sex influences
Pain score meaning may also reflect emotional and social influences. For instance, Chambers and Craig showed how children’s pain scores are biased upward or downward in response to emotional context (e.g., winning a race) or affectively laden anchors (smiley vs neutral faces) [29]. Preand post-operative pain ratings using various scales have been shown to be higher as a function of baseline state anxiety [4]. Furthermore, postoperative pain scores were found to strongly correlate with several measures of negative affect (i.e., how unpleasant, upset or afraid they felt at the time of assessment) [4,16]. These studies suggest that it may be difficult to discern pain intensity from other emotional states or feelings in the clinical setting [4,16]. Pain score meaning may also be influenced by sex. For instance, compared with boys, girls have scored immunization pain higher [24], associated lower pain scores with moderate-to-severe pain [14] and expressed satisfaction with analgesia at higher scores [18]. Additionally, boys who had higher masculinity ratings were found to be less willing to express pain compared with girls in experimental settings [30,31]. No differences have
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been found between the pain scores that boys and girls associate with treatment thresholds [14,17,18]. Conclusion & future perspective This article has highlighted some of the ongoing quandaries that plague clinicians when faced with interpreting and responding to children’s pain scores. Despite data supporting the psycho metric validity and reliability of self-report pain scales, evidence demonstrates wide variability in the clinical meaning that children attach to pain scores. Such findings suggest that it is inappropriate to use or establish standardized pain score thresholds for treatment or evaluation. In fact, doing so may jeopardize effective and safe pain management [32–35]. Instead, an individualized approach to the interpretation and use of pain scores is warranted to promote better treatment decisions [36]. Such an approach involves consideration of the clinical situation at hand and factors, including social–emotional contexts, that may influence the child’s self-report [12]. Critical analysis of the child’s self-report within context includes an evaluation of the medical condition and potential source(s) of pain (e.g., postoperative pain), physiologic signs and symptoms, behavioral observation and interpretation of behaviors with parents’ or others’ input, and consideration of the functional needs and goals of the patient [11,12]. Schiavenato and Craig have suggested that such a broad assessment culminates in a clinical judgment or final evaluation that invariably guides the decision to intervene [9]. Re-evaluating pain scores, behaviors and other factors following the effects of interventions may provide the best data for interpreting and understanding the meaning of the individual child’s self-report in order to best guide ongoing treatment decisions. Over the past decade, a growing consensus has emerged that self-reported pain scores – even when derived from scales purported to be valid and reliable – are an oversimplistic and insufficient means by which to make clinical decisions [7,9–12,37–39]. Over the next few years, we will probably see less emphasis on pain scores, and development of new methods that will better inform analgesic decisions and evaluation. Several investigators have suggested that the preferred method of pain assessment in children should consider both self-report and a behavioral or observer component [8,11]. Others have suggested incorporation of measures of physical functioning or pain impact, pain distress or,
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How reliable are ‘valid & reliable’ pain scores in the pediatric clinical setting? perhaps, acceptability of pain (e.g., ‘bearable’ vs ‘unbearable’) [22,37,40]. Such alternative methods need to be tried in the clinical setting and evaluated based on real outcomes that are important to the patient and clinician alike. To date, it remains unknown what the next best valid and reliable method of assessing children’s pain in the clinical setting will be. However, it will probably to diverge substantially from the simplistic pain intensity score. References
n
Papers of special note have been highlighted as: of interest n
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Financial & competing interests disclosure The author has no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties. No writing assistance was utilized in the production of this manuscript. Highlights some of the important considerations for use and interpretation of self-reported pain scores in children.
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