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Bennett RM, Bushmakin AG, Cappelleri JC, et al, Oregon Health and Science University, Portland, and other centers. Minimal clinically important difference in the fibromyalgia impact questionnaire. J Rheumatol. 2009;36:1304-1311.
In patients with fibromyalgia syndrome (FMS) who show moderate to severe impairment on the Fibromyalgia Impact Questionnaire (FIQ), a change of about 14% over 3 months probably is clinically important. A similar percentage change in stiffness also is likely to have clinical importance.
Bennett and associates analyzed data from 3 double-blind, randomized, placebo-controlled, parallel-group clinical trials of pregabalin in 2228 persons with FMS. The FIQ was completed at baseline and end point in all 3 studies, and the Patient Global Impression of Change (PGIC), a global assessment tool, was completed at end point. The investigators used the data to determine the lowest change in FIQ score (minimal clinically important difference [MCID]), indicative of a meaningful difference in FMS status.
The percentage change in the FIQ score in each PGIC category and the MCID for the FIQ total score were similar in each of the 3 studies. Overall, pooled across the 3 studies, the estimated MCID in the FIQ total score was 14.1%; the MCID in the FIQ stiffness item was 13.2%.
The authors noted that the results of these analyses should enhance the clinical utility of the FIQ in research and practice.