Development of the Japanese version of the Fibromyalgia Impact Questionnaire (JFIQ): psychometric assessments of reliability and validity

Aim: To perform a psychometric assessment of the Japanese version of the Fibromyalgia Impact Questionnaire (JFIQ). Methods: Data for the psychometric assessment were collected from Japanese fibromyalgia (FM) patients who visited a clinic. Analyses were performed to examine the reliability and validity of the JFIQ. Results: A total of 56 patients were included in the analysis. There was no remarkable floor or ceiling effect for the JFIQ item or total scores. In the analysis of reproducibility, the interclass correlation coefficients of each item score and total score ranged from 0.61 to 0.95. Cronbach's alpha coefficient was 0.92. For the concurrent validity, the total score and most of the item scores correlated to every domain of Short Form-36 or Beck Depression Inventory-II to a moderate or great extent. The results of the known-group comparisons indicated that the total score tended to increase with the increase in severity of FM and pain (P-values for trend < 0.05). Conclusion: This psychometric assessment demonstrated good reliability and validity of the JFIQ for use with Japanese FM patients. In the future, we expect that this questionnaire will be used in clinical studies and medical practice, and will be beneficial in the development of new therapies as well as for the comprehensive evaluation of patients' conditions in Japan.