Pain assessment in fibromyalgia and rheumatoid arthritis: influence of physical activity and illness perception

Pain visual analog scales (VAS) have been validated for clinical use in fibromyalgia (FM) and rheumatoid arthritis (RA) patients. There are potential limitations, however, not only considering their use as a continuous measurement, but also with regard to the influence of personal illness perceptions, habitual physical activity and other life-style features. The aim of the study was to ascertain whether different illness perception, physical activity and clinical and laboratory characteristics can predict the severity of perceived pain assessed by VAS.

This is an observational comparative study of forty consecutive out-patients, 20 of them with fibromyalgia and 20 with rheumatoid arthritis, treated by medical and physical therapy. Patients were assessed also by Pain VAS, Health Assessment Questionnaire (HAQ) disability index, Ritchie index, Baecke questionnaire for physical activity, Illness Perception Questionnaire (IPQr) and SF36.

Pain VAS is explained differently by some of the studied variables: in the total group HAQ and Ritchie index explain 29.8% of the variance; in the RA patients number of joints with pain and Ritchie index explain 52.7% of the variance; in FM patients total SF36 score and IPQr personal control dimension explains 44.7% of the variance. No definite role of anxiety and/or depression was found as predictor of perceived pain and disability.

Pain perception and complaint are explained by belief in FM patients: This seems to suggest the need for a more articulated cognitive approach; addressing both diagnostic and therapeutic interventions to anxiety/depression issues is not supported by our results.