Low Pain Thresholds in RA Reflect “Fibromyalgic” Disease

In patients with rheumatoid arthritis (RA), low pain thresholds reflect "fibromyalgic" RA (many tender points) and central pain sensitization with a prolonged disease duration. Early and intensive treatment that minimizes inflammation is likely to reduce central sensitization and minimize long-term RA pain; biologic therapies may play a crucial role.

Pollard and coworkers conducted a cross-sectional observational study of 105 outpatients with RA. To assess pain thresholds, they used the mean of 2 measurements made by a single assessor using a handheld digital algometer applied to the thumbnail. They recorded demographic data, physician global assessment, early morning stiffness, and 28-joint count Disease Activity Score (DAS 28) and its constituents. Fibromyalgic tender point assessment used methods recommended for diagnosis of fibromyalgia syndrome. Pain, fatigue, disability, and mental health were measured.

The median pain threshold was 289 kPa (interquartile range, 89 to 434 kPa). Pain thresholds showed high correlations with tender point counts, tender joint counts, fatigue, DAS 28, and disability. Moderate correlations included pain, depression and anxiety scores, and patient global assessment.

The authors suggested that over time, the burden of inflammation in RA may lead to persistence of pain as well as cause progressive joint damage and functional decline.