,oouma, of PsychosomnricRrsmxch, Vol Prmted m Great Britain.
35. No 415. pp. 599-607,
1991. 0
0541-3999/91 $3.00+.00 191 Pergamon Press plc
PREDICTING DISABILITY TIME USING FORMAL LOW BACK PAIN MEASUREMENT: THE LOW BACK PAIN SIMULATION FRANK
SCALE
LEAVITT
(Received 24 July 1990; accepted in revised form 30 January 1991)
Abstract-Objective evaluation of simulation in low back pain is currently not possible. A new simulation scale based on subject response to 103 pain words has shown promise in discriminating patients with low back pain from those simulating low back pain. Administration of this scale to 1679 individuals who were injured at work produced a 10.4% sample with scores in the simulation range. This subsample projected more intense pain and were disabled longer. These findings were replicated in a second study in which treating physicians rated the degree of physical pathology and symptom exaggeration blind to patient classification by the Low Back Pain Simulation Scale. Medical assessment indicated less organic pathology and greater symptom exaggeration among patients classified as simulators providing a measure of support for the validity of the simulation scale.
INTRODUCTION
IT IS widely believed that simulation exerts an influence on duration of disability among patient populations suffering from compensable low back injuries [ 1, 21. Two forms may be involved. In one form, simulation implies the conscious exaggeration of existing symptoms. In the other form, simulation implies the invention of symptoms that do not exist. Unfortunately, the exact importance of this influence is difficult to quantify. A recent survey shows major division among medical personnel who are probably the most knowledgeable about this issue. Estimates of the prevalence of simulation by orthopedic and neurosurgeons specializing in low back pain varied from a low of 1% to a high of 75% [31.There was more agreement at the low end, with 60% of the surgeons in agreement that it occurs in 5% or less in their clinical practices. Uncertainty concerning prevalence stems in part from the fact that objective criteria for identifying people who either exaggerate symptoms or invent them entirely are lacking. Some variables in the clinical examination are looked upon as more important in making the determination. Weakness to manual testing not seen in other activities, disablement disproportionate to objective findings and pain not following an organic pattern are clinical signs mentioned by a large majority of surgeons in a recent study 131 as important indicators of simulation; however, there has been no validation of these opinions. Recent research suggests that people who simulate pain to the back employ pain language differently than people with clinical pain 141. Forty-five variations have been found in the pain report of people who simulate pain when it does not exist [5] as well as in the pain report of people who consciously augment existing pain 161 that distinguishes them from patients with clinical pain. These differences formed the
Department of Psychology Chicago, IL 60612, U.S.A.
and Social Sciences,
Rush Medical
599
College,
1653 West Congress
Parkway,
600
F. LEAVITI
basis for identifying people simulating low back pain using the 103-item Low Back Pain Symptom Check List which incorporates the 45 pain words that differentiate this group from patients with clinical pain. While the simulation scale is promising, there are limitations that need to be addressed. In its individual development, the simulation group was composed of individuals selected from the general population who had no history of back pain. They were asked to simulate back pain and to select words from the Low Back Pain Symptom Check List to describe it. It is possible that people self-motivated to feign back pain do so for a variety of complex motivations that influence them to describe their pain differently. The purposes of this study are threefold. The major objective is to validate the simulation scale in a large out-patient sample of compensable back injured patients. Since people who simulate are generally portrayed as given to exaggerated claims of suffering and disability, 17, 81 it is our prediction that patients who produce scores in the simulation range will report more intense pain, and will show longer periods of disability. In addition, the simulation data will be analyzed for gender and racial differences, and for reliability in this clinical population. STUDY
I
Methods Subjects. The subjects were 1679 patients from the office practices of 16 orthopedic groups. Entry criteria included age (18-64 yr), race (white, black or hispanic), and back pain caused by a job related injury. Information on age, education, race, sex, duration of pain, disability time and pain intensity was drawn from a back pain questionnaire that is part of the clinical protocol used in these clinical settings. Disability time was coded as none, 1 month or less, 2-6 months, 7-12 months, and greater than 1 yr. Duration of pain was coded as O-l month, 2-6 months, 7-12 months and 1 yr or more. Low Back Pain Symprom Check List. The LBPSCL 151 is a self report, 103~item pain questionnaire which covers the range of sensory and affective pain sensations typically reported by patients with low back pain. Clinical patients with low back pain received the following instructions. ‘The words below describe different qualities of pain. Place an X in the boxes beside the words that best describe how your pain typically feels. You may check as many boxes as you wish that describe your typical pain this last week.’ Pain Intensify Measure. The Pain Intensity Measure is a linear analogue scale with self-ratings from 0 (no pain) to 100 (severest pain imaginable). The instructions were: ‘We need a more accurate idea of how severe your pain is. On a scale of O-100, in which 0 is no pain, and 100 is the most severe pain one can possibly imagine, what number would you give your average pain?’ Simularion classifcution. Patients were classified as simulators or non-simulators on the basis of scores on the 45 pain word Low Back Pain Simulation Scale. Discriminant values established for each word in the normative study 141 are shown in Table I. A discriminant score [91 was computed for each subject using linear combinations of the pain words endorsed. Pain words were weighted as part of a discriminant analysis so as to maximize discrimination between simulating and non-simulating groups. Patients were assigned to the group (simulator or non-simulator) for which probability of membership was highest. The minimal difference in probabilities for placement of patients in groups is 0.51 vs 0.49.
RESULTS
Characteristics of patients classified as simulators and non-simulators are presented in Table II. As can be seen the two groups are quite similar in respect of age, education, gender, race and duration of pain. In addition, there were no sex or racial The prevalence of the simulation pattern in differences in respect to simulation.
Predicting
disability TABLE
time using I.-Low
SIMULATION
Pain terms Gruelling Nagging Quivering Miserable Cruel Annoying Wrenching Pounding Momentary Stinging Unbearable Agonizing Piercing Steady Vicious Pricking Throbbing Numb Drilling Dreadful Drawing Rhythmic Hurting Burning Stabbing Itchy Sickening Tender Taut Crushing Pinching Killing Fearful Wretched Intense Superficial Deep Unlocalized Diffuse Surface Muscle Bone Joint Moving Electric
simulation
BACK
scores
601
PAIN
SCALE
Discriminant* function coefficients -0.55 0.29 -0.76 0.32 0.50 -0.53 0.81 0.54 0.67 -0.31 0.55 0.31 0.35 -0.44 -0.34 -0.49 0.28 -0.46 0.81 0.92 -0.37 0.65 -0.21 -0.37 0.53 1.01 0.31 -0.25 0.56 0.41 0.22 0.25 -0.45 0.66 0.30 0.78 0.26 -0.30 0.54 0.80 0.40 -0.50 -0.18 -0.39 -0.42
*Scaled weights used to assign subjects to groups. Negative values weigh towards normative pain group; positive values weigh towards simulation group.
males was 10.1%; in females 10.9%. The rate in white patients was 10.6%; in black patients 9.8 % ; and in hispanics 10.9%. The mean pain intensity score for simulators and non-simulators was 81.6 and 61.7 respectively. The 19.9 difference in favor of the simulation group was highly significant (F(1,1677) = 122.5, p
35. No 415. pp. 599-607,
1991. 0
0541-3999/91 $3.00+.00 191 Pergamon Press plc
PREDICTING DISABILITY TIME USING FORMAL LOW BACK PAIN MEASUREMENT: THE LOW BACK PAIN SIMULATION FRANK
SCALE
LEAVITT
(Received 24 July 1990; accepted in revised form 30 January 1991)
Abstract-Objective evaluation of simulation in low back pain is currently not possible. A new simulation scale based on subject response to 103 pain words has shown promise in discriminating patients with low back pain from those simulating low back pain. Administration of this scale to 1679 individuals who were injured at work produced a 10.4% sample with scores in the simulation range. This subsample projected more intense pain and were disabled longer. These findings were replicated in a second study in which treating physicians rated the degree of physical pathology and symptom exaggeration blind to patient classification by the Low Back Pain Simulation Scale. Medical assessment indicated less organic pathology and greater symptom exaggeration among patients classified as simulators providing a measure of support for the validity of the simulation scale.
INTRODUCTION
IT IS widely believed that simulation exerts an influence on duration of disability among patient populations suffering from compensable low back injuries [ 1, 21. Two forms may be involved. In one form, simulation implies the conscious exaggeration of existing symptoms. In the other form, simulation implies the invention of symptoms that do not exist. Unfortunately, the exact importance of this influence is difficult to quantify. A recent survey shows major division among medical personnel who are probably the most knowledgeable about this issue. Estimates of the prevalence of simulation by orthopedic and neurosurgeons specializing in low back pain varied from a low of 1% to a high of 75% [31.There was more agreement at the low end, with 60% of the surgeons in agreement that it occurs in 5% or less in their clinical practices. Uncertainty concerning prevalence stems in part from the fact that objective criteria for identifying people who either exaggerate symptoms or invent them entirely are lacking. Some variables in the clinical examination are looked upon as more important in making the determination. Weakness to manual testing not seen in other activities, disablement disproportionate to objective findings and pain not following an organic pattern are clinical signs mentioned by a large majority of surgeons in a recent study 131 as important indicators of simulation; however, there has been no validation of these opinions. Recent research suggests that people who simulate pain to the back employ pain language differently than people with clinical pain 141. Forty-five variations have been found in the pain report of people who simulate pain when it does not exist [5] as well as in the pain report of people who consciously augment existing pain 161 that distinguishes them from patients with clinical pain. These differences formed the
Department of Psychology Chicago, IL 60612, U.S.A.
and Social Sciences,
Rush Medical
599
College,
1653 West Congress
Parkway,
600
F. LEAVITI
basis for identifying people simulating low back pain using the 103-item Low Back Pain Symptom Check List which incorporates the 45 pain words that differentiate this group from patients with clinical pain. While the simulation scale is promising, there are limitations that need to be addressed. In its individual development, the simulation group was composed of individuals selected from the general population who had no history of back pain. They were asked to simulate back pain and to select words from the Low Back Pain Symptom Check List to describe it. It is possible that people self-motivated to feign back pain do so for a variety of complex motivations that influence them to describe their pain differently. The purposes of this study are threefold. The major objective is to validate the simulation scale in a large out-patient sample of compensable back injured patients. Since people who simulate are generally portrayed as given to exaggerated claims of suffering and disability, 17, 81 it is our prediction that patients who produce scores in the simulation range will report more intense pain, and will show longer periods of disability. In addition, the simulation data will be analyzed for gender and racial differences, and for reliability in this clinical population. STUDY
I
Methods Subjects. The subjects were 1679 patients from the office practices of 16 orthopedic groups. Entry criteria included age (18-64 yr), race (white, black or hispanic), and back pain caused by a job related injury. Information on age, education, race, sex, duration of pain, disability time and pain intensity was drawn from a back pain questionnaire that is part of the clinical protocol used in these clinical settings. Disability time was coded as none, 1 month or less, 2-6 months, 7-12 months, and greater than 1 yr. Duration of pain was coded as O-l month, 2-6 months, 7-12 months and 1 yr or more. Low Back Pain Symprom Check List. The LBPSCL 151 is a self report, 103~item pain questionnaire which covers the range of sensory and affective pain sensations typically reported by patients with low back pain. Clinical patients with low back pain received the following instructions. ‘The words below describe different qualities of pain. Place an X in the boxes beside the words that best describe how your pain typically feels. You may check as many boxes as you wish that describe your typical pain this last week.’ Pain Intensify Measure. The Pain Intensity Measure is a linear analogue scale with self-ratings from 0 (no pain) to 100 (severest pain imaginable). The instructions were: ‘We need a more accurate idea of how severe your pain is. On a scale of O-100, in which 0 is no pain, and 100 is the most severe pain one can possibly imagine, what number would you give your average pain?’ Simularion classifcution. Patients were classified as simulators or non-simulators on the basis of scores on the 45 pain word Low Back Pain Simulation Scale. Discriminant values established for each word in the normative study 141 are shown in Table I. A discriminant score [91 was computed for each subject using linear combinations of the pain words endorsed. Pain words were weighted as part of a discriminant analysis so as to maximize discrimination between simulating and non-simulating groups. Patients were assigned to the group (simulator or non-simulator) for which probability of membership was highest. The minimal difference in probabilities for placement of patients in groups is 0.51 vs 0.49.
RESULTS
Characteristics of patients classified as simulators and non-simulators are presented in Table II. As can be seen the two groups are quite similar in respect of age, education, gender, race and duration of pain. In addition, there were no sex or racial The prevalence of the simulation pattern in differences in respect to simulation.
Predicting
disability TABLE
time using I.-Low
SIMULATION
Pain terms Gruelling Nagging Quivering Miserable Cruel Annoying Wrenching Pounding Momentary Stinging Unbearable Agonizing Piercing Steady Vicious Pricking Throbbing Numb Drilling Dreadful Drawing Rhythmic Hurting Burning Stabbing Itchy Sickening Tender Taut Crushing Pinching Killing Fearful Wretched Intense Superficial Deep Unlocalized Diffuse Surface Muscle Bone Joint Moving Electric
simulation
BACK
scores
601
PAIN
SCALE
Discriminant* function coefficients -0.55 0.29 -0.76 0.32 0.50 -0.53 0.81 0.54 0.67 -0.31 0.55 0.31 0.35 -0.44 -0.34 -0.49 0.28 -0.46 0.81 0.92 -0.37 0.65 -0.21 -0.37 0.53 1.01 0.31 -0.25 0.56 0.41 0.22 0.25 -0.45 0.66 0.30 0.78 0.26 -0.30 0.54 0.80 0.40 -0.50 -0.18 -0.39 -0.42
*Scaled weights used to assign subjects to groups. Negative values weigh towards normative pain group; positive values weigh towards simulation group.
males was 10.1%; in females 10.9%. The rate in white patients was 10.6%; in black patients 9.8 % ; and in hispanics 10.9%. The mean pain intensity score for simulators and non-simulators was 81.6 and 61.7 respectively. The 19.9 difference in favor of the simulation group was highly significant (F(1,1677) = 122.5, p
