Reliability of an osteoporosis-targeted quality of life survey instrument for use in the community: OPTQoL

A brief Osteoporosis-Targeted Quality of Life (OPTQoL) questionnaire was pr eviously developed as a cross-sectional survey instrument to assess the com munity impact of osteoporosis on quality of life in women. The initial deve lopment process involving item generation through focus groups, item reduct ion, and content and construct validation yielded a 36-item questionnaire w ith three domains (physical difficulty, adaptations and fears) and 10 healt h-related questions. In the present study, test-retest reliability and inte rnal consistency of the questionnaire were assessed in a mail-based study w ith two clinical sites. Two hundred women (50 with severe osteoporosis, 50 with osteopenia, 50 with normal bone mineral density (BMD) and 50 with oste oarthritis and normal BMD), aged 43-84 years, completed the self-administer ed questionnaire initially and again about 2 weeks later. Using weighted ka ppas, agreement between questionnaire administrations ranged from 0.60 to 0 .80 for most of the individual items. Intraclass correlation coefficients t o assess reliability for the domain scores were 0.93 (physical difficulty), 0.82 (adaptations) and 0.88 (fears). Internal consistency of each of the d omains was also high, with Cronbach's alpha coefficients ranging from 0.89 to 0.91. Four items were dropped from the 36-item questionnaire due to high percentage of 'not applicable' responses. Results of the analyses support the validity and reliability of this instrument as a cross-sectional survey tool for assessing the impact of osteoporosis on quality of life in women living in the community. The questionnaire has been translated and cultural ly adapted into seven languages to allow cross-cultural studies of the comm unity impact of osteoporosis.