Background: The Fibromyalgia Impact Questionnaire (FIQ) is a patient-reported outcome that evaluates the impact of fibromyalgia (FM) on daily life. This study evaluated the relationships between the functional status of FM patients, measured with the FIQ at baseline, and median time to a clinically relevant pain reduction.
Methods: Data were derived from two randomised, placebo-controlled trials that evaluated pregabalin 300, 450 and 600 mg/day for the treatment of FM. The Kaplan–Meier (nonparametric) method was applied to estimate median times to ‘transient’ and ‘stable’ events. The transient event was defined as a ≥ 27.9% improvement on an 11-point daily pain diary scale (0 = no pain, 10 = worst possible pain), and the stable event was defined as the mean of the daily improvements ≥ 27.9% relative to baseline over the subsequent study duration starting on the day of the transient event. A parametric model using time-to-event analysis was developed for evaluating the relationship between baseline FIQ score and the median time to these events.
Results: Median time was longer among patients treated with placebo relative to pregabalin for the transient events (11–12 days vs. 5–7 days) and stable events (86 days vs. 13–29 days). A significant association was observed between baseline FIQ scores and median time to transient and stable events (p < 0.001). Median times to events were similar between the studies. For transient pain reduction events, median times ranged from 3.0 to 4.5 days for baseline FIQ scores of 10, and 9.1–9.6 days for FIQ scores of 100; for stable pain reduction events, the median time ranged from 11.0 to 13.0 days and from 27.0 to 28.5 days for baseline FIQ scores of 10 and 100 respectively.
Conclusions: Time to a clinically relevant reduction in pain was significantly associated with FM severity at baseline as measured by the FIQ. Such an analysis can inform patient and physician expectations in clinical practice.