Correlations between fibromyalgia symptom and function domains and patient global impression of change: a pooled analysis of three randomized, placebo-controlled trials of pregabalin.

OBJECTIVE

The objective of the study was to conduct an analysis of pooled data from pregabalin fibromyalgia clinical trials to determine which fibromyalgia symptom and function domains drive patient perception of improvement.

DESIGN

Data from three double-blind, placebo-controlled trials of pregabalin in fibromyalgia patients were pooled for this analysis. Changes in independent variables, including the Medical Outcomes Study 36-item Short-Form Health Survey, Medical Outcomes Study-Sleep Scale, sleep quality score from the daily sleep diary, pain score from the daily pain diary, Fibromyalgia Impact Questionnaire, and Multidimensional Assessment of Fatigue were analyzed as predictors of outcome on the dependent variable, Patient Global Impression of Change (PGIC). Correlation analysis assessed relationships between the independent variables and PGIC. Cluster analysis identified dependencies among variables, and a shrinkage and selection method and stepwise logistic regression determined rank order of variables.

RESULTS

Improvement in PGIC at endpoint showed highest correlation with pain improvement, fatigue, sleep, and work and physical function (0.4 < r < 0.6). Cluster analysis identified three main clusters of symptoms at endpoint: mood (anxiety and depression), pain and sleep, and function and fatigue. Pain was ranked as the most important outcome explaining variability in PGIC, followed by fatigue and sleep.

CONCLUSIONS

Pain, fatigue, and sleep associate most strongly with improvement in PGIC. Physical- and work-related function also correlated with patients' overall assessment of improvement. These domains and their respective outcome measures can be used to improve assessment of patients' response to treatment.