114
A Modified Quality-of-Life Measure for Youths: Psychometric Properties GARY M. INGERSOLL, PhD; DAVID G. MARRERO, PhD Indiana University Diabetes Research and Training Center Indianapolis, Indiana
In the Diabetes Control and
Complication Trial (DCCT), a Diabetes Quality of Life (DQOL) measure was developed to assess the
psychosocial impact of intensified regimens. Its applicability for use with children and adolescents was limited by the exclusion criteria of the DCCT. In this study, the DQOL
modifiedfor specific use in young diabetes populations. The was
result is an instrument composed of three intercorrelated scales—a Diabetes Life Satisfaction scale, a Disease Impact scale, and a
Disease-Related Worries scale—with satisfactory levels of reliability. While the scale variances were independent of
glycosylated hemoglobin values, they were related to adolescents’ perception of their general health status. Self-perceived quality oflife related to diabetes management is an important alternative outcome for diabetes education programs.
Recently, the Diabetes Control and Complication Trial (DCCT) Research Group described a measure entitled the Diabetes Quality of Life Instrument (DQOL).’ This instrument was developed to assess subjects’ perceptions of the impact of an intensified regimen on their general satisfaction with life and on concerns over social and vocational issues related to their diabetes. Recognition by the DCCT research group of the importance of quality of life as a central outcome, in addition to measures of metabolic control, reflects an important advance in contemporary thinking about the clinical treatment of diabetes. Beyond their use in evaluating the impact of various therapeutic regimens, quality of life measures hold important promise for evaluation of other aspects of diabetes management, especially diabetes education programs. This is particularly relevant in light of the clear mandate for such evaluations in the American Diabetes Association’s revised manual for recognition of diabetes education programs. ? Examination of the procedures used in the DCCT’s evaluation of their DQOL instrument reveals that the original sample was predominately adult; children and adolescents under the age of 13 were excluded. The final version’ had 46 core items and 16 auxiliary questions (for adolescents) organized into four primary scales: (1) satisfaction with life with diabetes ; (2) rmpact of diabetes on one’s life; (3) wrrres related to social and vocational issues; and (4) worries related to longterm sequelae of the disease. Reliability values ranged from .66 to .92 and test-retest reliabilities ranged from .78 to .92. The authors indicated that the reliability of the &dquo;worries&dquo; scale was lower than desired. Although the original instrument was intended for assessment within the context of the DCCT, it was presumed to be applicable to a wider range of people with insulin-dependent diabetes mellitus (IDDM). However, many of the DQOL items are of limited relevance to the lives of children and adolescents. Hence we deemed it I
At the time of this study, Dr Ingersoll was Director of Development and Evaluation Core, Indiana UmversUy DRTC, and Professor. Department ofCounselmgand Educauonal Psychology, Indiana University School of Medicme, Indianapolis. He has recently assumed the posmon of Associate Dean for Research and Dcvclopmcnt. School of Education, Indiana Umversuy, Bloommgton. Dr Marrero is Director of Training, Indiana UmversUy DRTC. This study was supported in part by grants to the Indiana University Diabetes Research and Tramng Center from the National Institutes of Health (PHS P60-DK-20542), Bethesda. Md, and from Miles Laboratory. Inc, Elkhart, Ind. Reprint requests to Gary M. Ingersoll, PhD. Indiana Umversuy Diabetes Research and Tramng Center. Regenstrief InsW ute. 5th Floor, 10011 West Tenth Street, Indianapolis, IN 46202. Downloaded from tde.sagepub.com at CORNELL UNIV on June 22, 2015
115
useful to modify the DQOL for specific use with youth populations. The purpose of the present study was to adapt the original DQOL for specific use with older children and adolescents and to assess the psychometric properties of the resultant instrument.
Methods Patient Selection and Setting Subjects for this study were 74 children and adolescents with IDDM recruited sequentially from the patient population of the James Whitcomb Riley Hospital for Children of the Indiana University Medical School. Riley Hospital is the only pediatric hospital in the state of Indiana and serves a broad range of children of divergent social and ethnic backgrounds. Subjects were excluded if there were indications of psychopathology or intellectual retardation. Informed consent was obtained from both the participants and their parents in accord with procedures approved by the Indiana University-Purdue University at Indianapolis Institutional Review Board. One child’s parents declined to allow their child to participate. The sample was composed of 46 boys and 28 girls with a mean age of 16.0 years (SD 2.8; range 10.8 to 21.8 years). The mean duration of IDDM in the sample was 5.6 years (SD 4.1; range 0 to 2 years). Each subject was administered the modified DQOL and tested for total stable glycosylated hemoglobin (HbAI) using a microcolumn procedure3 by the Immunoassay Core of the Indiana University Diabetes Research and Training Center. =
=
=
=
Results
A summary of the results of the
=
=
Instrument Prior to field testing the instrument, we had the items independently reviewed by a pediatric diabetologist, a nurse practitioner, a social worker, and an educational psychologist, all of whom specialize in pediatric diabetes care. In the preliminary analysis of the DCCT version of the DQOL, items of limited value for children and adolescents were dropped (eg, &dquo;How often do you worry about whether you will be denied insurance?&dquo;). In addition, items relating to school life and peers were included. Items were then field tested with a sample of 15 youths (ages 1 1 to 18) selected at random from the Riley Hospital population. These subjects were not included in the subsequent analysis. As a result of the pilot test, the wording of the questions was simplified, when appropriate, to make them more readable. Additionally, the original DCCT response format for the Satisfaction with Life scale was found to be confusing and was therefore modified to a simpler 5-point Likert scale. The revised instrument was composed of a 17-item Diabetes Life Satisfaction scale, a 26-item Disease Impact scale, and a 13-item Disease-Related Worries scale. Also included was a general self-rating of overall health:
Compared with others
your age, would you say that your
health is: 0 Excellent
O Good
O Fair
reliability
of the DQOL is presented in Table 1. ,411 17 items of the Life Satisfaction scale contributed to overall scale variance; the resulting reliability estimate (Cronbach alpha) was .85. The Disease Impact scale was modified by removing three items (&dquo;How often do you have low blood sugar?&dquo; &dquo;How often do you tell others about your diabetes?&dquo; and &dquo;How often do you find that close family members tease you about your diabetes?&dquo;) that did not correlate with total scale variance. The modified 23-item scale had a Cronbach alpha of .83. The Disease-Related Worries scale was modified to an I I -item scale because two items (&dquo;How often do you worry about whether you will be able to complete your education?&dquo; and &dquo;How often do you worry about whether you will miss work?&dquo;) were uncorrelated with total scale variance. The modified 1 1-item scale had a Cronbach alpha of .82. The resulting instrument is presented in the Figure. (A complete listing of items and item-total correlation statistics are available upon request from the authors.) The intercorrelations of the three DQOL scales and the scales with gender, age, disease duration, and self-rated health are summarized in Table 2. As seen in Table 2, the three scales are not statistically independent. That is, the more diabetes is seen to have an impact on daily living, the more likely adolescents are to report lower life satisfaction (r -.48, P
A Modified Quality-of-Life Measure for Youths: Psychometric Properties GARY M. INGERSOLL, PhD; DAVID G. MARRERO, PhD Indiana University Diabetes Research and Training Center Indianapolis, Indiana
In the Diabetes Control and
Complication Trial (DCCT), a Diabetes Quality of Life (DQOL) measure was developed to assess the
psychosocial impact of intensified regimens. Its applicability for use with children and adolescents was limited by the exclusion criteria of the DCCT. In this study, the DQOL
modifiedfor specific use in young diabetes populations. The was
result is an instrument composed of three intercorrelated scales—a Diabetes Life Satisfaction scale, a Disease Impact scale, and a
Disease-Related Worries scale—with satisfactory levels of reliability. While the scale variances were independent of
glycosylated hemoglobin values, they were related to adolescents’ perception of their general health status. Self-perceived quality oflife related to diabetes management is an important alternative outcome for diabetes education programs.
Recently, the Diabetes Control and Complication Trial (DCCT) Research Group described a measure entitled the Diabetes Quality of Life Instrument (DQOL).’ This instrument was developed to assess subjects’ perceptions of the impact of an intensified regimen on their general satisfaction with life and on concerns over social and vocational issues related to their diabetes. Recognition by the DCCT research group of the importance of quality of life as a central outcome, in addition to measures of metabolic control, reflects an important advance in contemporary thinking about the clinical treatment of diabetes. Beyond their use in evaluating the impact of various therapeutic regimens, quality of life measures hold important promise for evaluation of other aspects of diabetes management, especially diabetes education programs. This is particularly relevant in light of the clear mandate for such evaluations in the American Diabetes Association’s revised manual for recognition of diabetes education programs. ? Examination of the procedures used in the DCCT’s evaluation of their DQOL instrument reveals that the original sample was predominately adult; children and adolescents under the age of 13 were excluded. The final version’ had 46 core items and 16 auxiliary questions (for adolescents) organized into four primary scales: (1) satisfaction with life with diabetes ; (2) rmpact of diabetes on one’s life; (3) wrrres related to social and vocational issues; and (4) worries related to longterm sequelae of the disease. Reliability values ranged from .66 to .92 and test-retest reliabilities ranged from .78 to .92. The authors indicated that the reliability of the &dquo;worries&dquo; scale was lower than desired. Although the original instrument was intended for assessment within the context of the DCCT, it was presumed to be applicable to a wider range of people with insulin-dependent diabetes mellitus (IDDM). However, many of the DQOL items are of limited relevance to the lives of children and adolescents. Hence we deemed it I
At the time of this study, Dr Ingersoll was Director of Development and Evaluation Core, Indiana UmversUy DRTC, and Professor. Department ofCounselmgand Educauonal Psychology, Indiana University School of Medicme, Indianapolis. He has recently assumed the posmon of Associate Dean for Research and Dcvclopmcnt. School of Education, Indiana Umversuy, Bloommgton. Dr Marrero is Director of Training, Indiana UmversUy DRTC. This study was supported in part by grants to the Indiana University Diabetes Research and Tramng Center from the National Institutes of Health (PHS P60-DK-20542), Bethesda. Md, and from Miles Laboratory. Inc, Elkhart, Ind. Reprint requests to Gary M. Ingersoll, PhD. Indiana Umversuy Diabetes Research and Tramng Center. Regenstrief InsW ute. 5th Floor, 10011 West Tenth Street, Indianapolis, IN 46202. Downloaded from tde.sagepub.com at CORNELL UNIV on June 22, 2015
115
useful to modify the DQOL for specific use with youth populations. The purpose of the present study was to adapt the original DQOL for specific use with older children and adolescents and to assess the psychometric properties of the resultant instrument.
Methods Patient Selection and Setting Subjects for this study were 74 children and adolescents with IDDM recruited sequentially from the patient population of the James Whitcomb Riley Hospital for Children of the Indiana University Medical School. Riley Hospital is the only pediatric hospital in the state of Indiana and serves a broad range of children of divergent social and ethnic backgrounds. Subjects were excluded if there were indications of psychopathology or intellectual retardation. Informed consent was obtained from both the participants and their parents in accord with procedures approved by the Indiana University-Purdue University at Indianapolis Institutional Review Board. One child’s parents declined to allow their child to participate. The sample was composed of 46 boys and 28 girls with a mean age of 16.0 years (SD 2.8; range 10.8 to 21.8 years). The mean duration of IDDM in the sample was 5.6 years (SD 4.1; range 0 to 2 years). Each subject was administered the modified DQOL and tested for total stable glycosylated hemoglobin (HbAI) using a microcolumn procedure3 by the Immunoassay Core of the Indiana University Diabetes Research and Training Center. =
=
=
=
Results
A summary of the results of the
=
=
Instrument Prior to field testing the instrument, we had the items independently reviewed by a pediatric diabetologist, a nurse practitioner, a social worker, and an educational psychologist, all of whom specialize in pediatric diabetes care. In the preliminary analysis of the DCCT version of the DQOL, items of limited value for children and adolescents were dropped (eg, &dquo;How often do you worry about whether you will be denied insurance?&dquo;). In addition, items relating to school life and peers were included. Items were then field tested with a sample of 15 youths (ages 1 1 to 18) selected at random from the Riley Hospital population. These subjects were not included in the subsequent analysis. As a result of the pilot test, the wording of the questions was simplified, when appropriate, to make them more readable. Additionally, the original DCCT response format for the Satisfaction with Life scale was found to be confusing and was therefore modified to a simpler 5-point Likert scale. The revised instrument was composed of a 17-item Diabetes Life Satisfaction scale, a 26-item Disease Impact scale, and a 13-item Disease-Related Worries scale. Also included was a general self-rating of overall health:
Compared with others
your age, would you say that your
health is: 0 Excellent
O Good
O Fair
reliability
of the DQOL is presented in Table 1. ,411 17 items of the Life Satisfaction scale contributed to overall scale variance; the resulting reliability estimate (Cronbach alpha) was .85. The Disease Impact scale was modified by removing three items (&dquo;How often do you have low blood sugar?&dquo; &dquo;How often do you tell others about your diabetes?&dquo; and &dquo;How often do you find that close family members tease you about your diabetes?&dquo;) that did not correlate with total scale variance. The modified 23-item scale had a Cronbach alpha of .83. The Disease-Related Worries scale was modified to an I I -item scale because two items (&dquo;How often do you worry about whether you will be able to complete your education?&dquo; and &dquo;How often do you worry about whether you will miss work?&dquo;) were uncorrelated with total scale variance. The modified 1 1-item scale had a Cronbach alpha of .82. The resulting instrument is presented in the Figure. (A complete listing of items and item-total correlation statistics are available upon request from the authors.) The intercorrelations of the three DQOL scales and the scales with gender, age, disease duration, and self-rated health are summarized in Table 2. As seen in Table 2, the three scales are not statistically independent. That is, the more diabetes is seen to have an impact on daily living, the more likely adolescents are to report lower life satisfaction (r -.48, P
