Pain mechanisms tied to disease activity in DMARD-treated RA

A recent study has shown the importance of identifying and treating aberrant peripheral and central pain regulation in patients with rheumatoid arthritis (RA) who are either initiating or switching to disease-modifying antirheumatic drug (DMARD) treatment.

Some 176 patients with RA underwent disease activity evaluation before and after starting a DMARD using the Disease Activity Score in 28 joints (DAS28). The researchers used quantitative sensory testing (QST), including pressure pain thresholds (PPTs), temporal summation, and conditioned pain modulation (CPM), to assess pain mechanisms.

Finally, the QST modalities most predictive of DAS28 after DMARD therapy were determined using the regression tree methodology.

The researchers identified four groups defined by baseline DAS28 category and either knee PPT (a combined measure of peripheral and central nervous system dysregulation) or CPM (a measure of descending pain inhibition).

Lower knee PPT (≤4.65 kgf) was the strongest predictor of post-treatment disease activity (group 1 vs group 2: mean DAS28, 2.8 vs 3.5) among patients starting with low/moderate disease activity.

Among those starting with high baseline disease activity, less efficient descending pain modulation (CPM ≤1.55) was found to be the most robust predictor of higher post-treatment disease activity (group 3 vs group 4: DAS28, 3.4 vs 4.6).

“Although pain affects the assessment of disease activity in patients with RA, pain is not always directly related to peripheral joint inflammation,” the researchers said. “Peripheral and central nervous system regulatory mechanisms also affect pain perception.”