Psychometric evaluation of the Cushing's Quality-of-Life questionnaire.
Abstract | BACKGROUND: OBJECTIVE: Reliability, validity, the ability to detect change, and a minimal important difference (MID) were evaluated for the CushingQOL questionnaire using data from patients diagnosed with CD who participated in the phase III clinical trial designed to assess the safety and efficacy of different doses of pasireotide. METHODS: Adult patients (n = 162) with CD participated in a randomized, double-blind, multinational, phase III clinical trial. Patients received subcutaneous pasireotide (600 μg or 900 μg) twice daily for 3 months (double blind). After 3 months, some patients were unblinded based on their mean urinary free cortisol (mUFC) levels and were given the chance to increase their dosage, while the other patients remained blinded. At month 6, an open-label 6-month period began. The CushingQOL questionnaire was self-administered four times (baseline [n = 160], and at months 3 [n = 134], 6 [n = 113], and 12 [n = 76]). A confirmatory factor analysis (CFA) was conducted. Reliability estimates were calculated for internal consistency (coefficient alpha) and test retest (intraclass correlation coefficients [ICCs]) for patients with stable hypercortisolism at month 3 and month 6. Construct validity hypotheses (correlations), mean differences in known groups (ANOVAs), and responsiveness effect sizes (Guyatt's) were estimated based on measures of cortisol, body mass index (BMI), waist circumference, weight, facial rubor (redness), striae ( stretch marks), bruising, supraclavicular fat pad, dorsal fat pad, and results of the Beck Depression Inventory II (BDI-II). The half-standard deviation distribution method was used to estimate MID. RESULTS: CFA loadings supported a one-factor solution for the CushingQOL questionnaire items. Internal consistency reliability (0.87-0.88) and ICCs (0.87) were high. Construct validity hypotheses were in the anticipated direction. Changes in CushingQOL scores were moderately correlated with changes in mUFC levels, in BMI, and in weight. Mean scores for minimally depressed patients were significantly higher (indicating better HR-QOL) than for severely depressed patients. Moderate Guyatt's responsiveness effect sizes were observed for patients who achieved reductions in weight, BMI, and waist circumference. Using the half-standard deviation method, an estimate of the MID was computed as 10.1. CONCLUSIONS: This study provided evidence within the context of a longitudinal design that the CushingQOL questionnaire is a reliable, valid, and responsive instrument for the assessment of HR-QOL in adults with CD in accordance with recommendations set forth by regulatory agencies in the USA and Europe.
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Authors | Lauren M Nelson, Anna Forsythe, Lori McLeod, Sonia Pulgar, Mario Maldonado, Theresa Coles, Yanqiong Zhang, Susan M Webb, Xavier Badia |
Journal | The patient
(Patient)
Vol. 6
Issue 2
Pg. 113-24
( 2013)
ISSN: 1178-1653 [Print] New Zealand |
PMID | 23575965
(Publication Type: Journal Article, Multicenter Study, Research Support, Non-U.S. Gov't, Validation Study)
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Chemical References |
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Topics |
- Adolescent
- Adult
- Aged
- Clinical Trials, Phase III as Topic
- Cushing Syndrome
(therapy)
- Factor Analysis, Statistical
- Female
- Health Status
- Humans
- Longitudinal Studies
- Male
- Middle Aged
- Psychometrics
- Quality of Life
- Randomized Controlled Trials as Topic
- Reproducibility of Results
- Somatostatin
(analogs & derivatives, therapeutic use)
- Surveys and Questionnaires
- Treatment Outcome
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