Terrence Steyer, M.D.
Chair, Department of Family Medicine
J.G. Kotsanos, L. Vignati, W. Huster, C. Andrejasich, M.B. Boggs, A.M. Jacobson, D. Marrero, S.D. Mathias, D. Patrick, S. Zalani, J. Anderson (1997)
The DQLCTQ is a self-administered questionnaire composed of 142 items (including 4 demographic questions) comprising 34 generic and diabetes-specific domains and was designed for use in a clinical trial to measure the QOL changes in patients receiving insulin lispro.. QOL domains and their importance were initially developed from patient and clinical focus groups, written questionnaires, and discussions The questions in this survey were drawn from previously published questionnaires including the Medical Outcomes Study (MOS), the SF-20 and SF-36, and the DQOL. Additional questions were created to address parameters not already in the literature. The four primary outcome (diabetes specific) domains are energy/fatigue, health distress, treatment flexibility, and treatment satisfaction. French and German translations of the questionnaire were also included in the reliability and validation tests of the instrument. The original population consisted of both Type I and Type II diabetics in four countries and showed favorable internal reliability and validity. The authors state that validity of the instrument was very favorable, but they do not provide any statistics. Internal reliability, as measured by Cronbach's alpha, ranged from 0.81 to 0.90 for the four primary outcomes. No statistics were provided for the 30 generic domains.
A sample of 942 patients in Canada, France, Germany, and the United States, containing both Type 1 and Type 2 diabetics, was used to further test the DQLCTQ and develop a revised version (Shen et al. 1999). As a measure of reliability, Cronbach's alpha were acceptable (>0.70) for all domains except social worry and diabetes worry from the DQOL. For the four primary domains test-retest reproducibility was excellent with correlation coefficients above 0.80. Validity was measured using a number of external comparisons. Patients with type 1 diabetes scored higher than patients with type 2 diabetes. Patients with good self-perceived control of their diabetes had significantly higher scores than patients with poor self-perceived control. Patients with tight control of their HbA1c levels had higher scores than patients with poor control. From the reliability and validation analyses of the entire questionnaire, a revised version (DQLCTQ-R) was developed which contains only 57 questions and eight generic and disease-specific domains: physical function, energy/fatigue, health distress, mental health, satisfaction, treatment satisfaction, treatment flexibility, and frequency of symptoms. The domains were selected as those which showed the greatest reliability and validity, contained more than one question, and did not duplicate other domains. The revised version can be completed in about 10 minutes.
Validity and reliability of the DQLCTQ has not been investigated specifically for elderly populations although the mean age of type 2 diabetics in the initial surveys was 58.2.
No studies involving minority populations have been conducted.
The original publication (Kotsanos et al. 1997) evaluated the change in QOL in patients on a regimen of lispo. The outcome measures of Treatment Satisfaction and Treatment Flexibility were significantly improved over the course of the trial for Type 1 diabetics. The second study (Shen et al. 1999) assessed the responsiveness of the tool to monitor changes in patient QOL over the course of a clinical trial. Four domains (treatment satisfaction, health/distress, mental health, and satisfaction) showed good responsiveness to insulin treatment after a 6-month period. The other four domains showed no responsiveness to treatment.
The revised measure is internally reliable, externally valid, responsive (at least in part) to a treatment regimen, and shows good test-retest reproducibility. The survey has been translated into French and German with no loss in its value. It has been tested with large numbers of patients in several countries. It has not, however, been tested in minority populations or specifically in elderly populations.
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Kotsanos, J.G., L. Vignati, W. Huster, C. Andrejasich, M.B. Boggs, A.M. Jacobson, D. Marrero, S.D. Mathias, D. Patrick, S. Zalani, J. Anderson (1997) Health-related quality-of-life results from multinational clinical trials of insulin lispro. Diabetes Care 20, 948-958.
Shen, W., J.G. Kotsanos, W.J. Huster, S.D. Mathias, C.M. Andrejasich, D.L. Patrick (1999) Development and validation of the Diabetes Quality of Life Clinical Trial Questionnaire. Med. Care, 37, AS45-AS66, Lilly Suppl.