The following is a summary of “Pain Mechanisms Associated With Disease Activity in Patients With Rheumatoid Arthritis Treated With Disease-Modifying Antirheumatic Drugs: A Regression Tree Analysis,” published in the June 2023 issue of Rheumatology by Wohlfahrt et al.

Although pain influences the evaluation of disease activity in rheumatoid arthritis (RA) patients, pain is not always directly related to peripheral joint inflammation. Regulatory mechanisms of the peripheral and central nervous systems also influence pain perception. The researchers used regression tree methodology to identify the mechanisms most predictive of disease activity after disease-modifying antirheumatic drug (DMARD) treatment. About 176 patients with RA were evaluated for disease activity using the Disease Activity Score in 28 Joints (DAS28) before and after initiating a DMARD. 

Pain mechanisms were evaluated using quantitative sensory testing (QST), including pressure pain thresholds (PPTs), temporal summation, and conditioned pain modulation (CPM). Utilizing regression tree methodology, the QST modalities most predictive of DAS28 after DMARD treatment were identified. This analysis identified four groups based on the DAS28 category at baseline: knee PPT (a combined measure of peripheral and central nervous system dysregulation) or CPM (a measure of descending pain inhibition). Lower knee PPT (PPT ≤ 4.65 kgf) most strongly predicted higher posttreatment disease activity among patients with low/moderate disease activity at baseline (group 1 mean DAS28 2.8 [SD 1.0] versus group 2 mean DAS28 3.5 [SD 1.0]). 

Less efficient descending pain modulation (CPM≤ 1.55) most strongly predicted higher posttreatment disease activity among patients with high baseline disease activity (group 3 mean DAS28 3.4 [SD 1.4] vs. group 4 mean DAS28 4.6 [SD 1.1]). These findings highlight the significance of identifying and treating abnormal peripheral and central pain regulation in rheumatoid arthritis (RA) patients initiating or switching DMARD therapy.

Source: jrheum.org/content/50/6/741