The reliability and validity of the Turkish version of the Quality of Life Questionnaire of the European Foundation for Osteoporosis-31 (QUALEFFO-31)

SUMMARY: This study reveals the Turkish version of QUALEFFO-31 has a sufficient level of reliability, validity, and psychometric properties. The questionnaire, which is potentially capable of differentiating patients with fractures, does not appear to have the differential capacity in terms of osteoporosis. PURPOSE: This study aims to conduct the reliability and validity study of QUALEFFO-31 in Turkish and to evaluate the capacity of the questionnaire to distinguish patients in terms of osteoporosis. METHODS: The original English version was translated into Turkish by two translators whose native language was Turkish. Subsequently, this Turkish version was translated back into English by two different bilingual translators whose native language was English. After this preliminary questionnaire was tested in 30 patients, words, terminology, information errors, and parts difficult to understand were revised, and the questionnaire was finalized. Internal consistency and test–retest analyses were used for the reliability study. For the validity study, convergent-discriminant validity, concurrent validity, factor analysis, known-group validity, and receiver operating characteristic (ROC) analyses were performed. RESULTS: A total of 111 patients were evaluated. Internal consistency levels were optimal except for the mental function. ICC coefficients showed good retest reliability for all domains and total tests. The convergent and discriminant validity ratios for the mental function domain were 78% for both and 100% for the other domains. There was a moderate and good negative correlation between QUALEFFO-31 and SF-36 domains which had similar names. Exploratory factor analysis revealed 3 structures. However, there was a spread to the other factors in physical function domain items. Confirmatory factor analysis (CFA) markers were not at a very good fitting level except for the relative chi-square index. When CFA was performed according to the assumed model, the fitting level increased in all analyses. There was no significant differential capacity in terms of osteoporosis or fracture for either QUALEFFO-31 or SF-36. CONCLUSION: The Turkish version of QUALEFFO-31 has a sufficient level of reliability, validity, and psychometric properties. Nevertheless, improvements in pain and mental function domains and some changes applying to the model may increase the psychometric capacity of the questionnaire. The questionnaire, which is potentially capable of differentiating patients with fractures, does not appear to have the differential capacity in terms of osteoporosis. CLINICALTRIALS.GOV IDENTIFIER: NCT04259099 (date of registration: February 6, 2020) SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s11657-021-00997-4.