Development and validation of a quality of life instrument for Kashin-Beck disease: an endemic osteoarthritis in China

Objectives: To develop and validate a disease-specific Quality of Life (QOL) measure for a specialized osteoarthritis (OA)-Kashin-Beck disease (KBD). Methods: The standard methodology used for developing QOL instruments was employed. In phase 1, initially a group of health care professionals (HCPs) and KBD patient defined the overall concept of KBDQOL. It was followed by generation of an item pool through literature review, in-depth interview of 20 KBD patients and eight KBD HCPs and four focus group discussions. In phase 2, 368 KBD patients were interviewed and the reinterview of 95 participants, 10-14 days later assessed the reproducibility of the KBDQOL instrument. Results: A 37 items draft instrument was devised during phase 1. Principal Component Analysis (PCA) revealed six domains: physical function, activity limitation, social support, economics, mental health, and general health. Cronbach's alphas of six domains ranged from 0.77 to 0.90. The test-retest reliability (intraclass co-relation coefficient) of six domains was satisfactory, and ranged from 0.73 to 0.90. The smallest detectable change ranged from 13.2 to 30.2 points at the individual level and from 1.4 to 3.1 points at the group level for different domains. The construct validity was adequate when co-related with the EQ-5D (spearman co-relation coefficients: 0.49-0.61) and WHOQOL-BREF (spearman co-relation coefficients: 0.53-0.68). This resulted into the final version of KBDQOL instrument having 28 items and six domains. Conclusions: The KBDQOL is a simple and easy to use 28-item six dimensional questionnaire. The measure has been developed as a true patient-based questionnaire and demonstrates good measurement properties. (C) 2012 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.