Variation in pressure pain threshold correlation with rheumatic arthritis not with inflammatory parameters

Abstract

Background Pain is a chief symptom of rheumatoid arthritis (RA) indicating the disease flare. Variation in pain sensitivity with inflammatory load may assist in measuring the disease activity. Tender joint counts, one of the currently used pain measures, is more a measure of active joints rather than the pain. Although visual analogue scale (VAS) reflects the perception of pain, it does not indicate the true change in the pain. Aim To evaluate whether pressure pain threshold (PPT) represents disease activity by comparing it with DAS-28 and inflammatory markers like ESR and CRP. Materials and mgethods Twenty freshly diagnosed female RA subjects were recruited after careful exclusion of patients with fibromyalgia (FM). They were assessed for tender joint count, swollen joint count, visual analogue scale (pain/general health), ESR, and CRP during their three consecutive follow-up of six week intervals. PPT was measured using digital algometer at three pairs of joint areas (metacarpophalangeals, wrists and most inflamed joint) and at three FM tender point sites (sub-occipital, mid-trapezius and buttocks). Arithmetic mean of all areas (average PPT) and average PPT of FM points were calculated. The data was analyzed using Pearson correlation co-efficient, Deming regression analysis, and correlation of change. Results Average PPT and PPT of most inflamed joint have moderate to large correlation with DAS-ESR and DAS-CRP. In contrast, small to trivial correlation with ESR and CRP was noted. Similar results were seen for FM tender point sites. Conclusion PPT at inflamed as well as at FM sites correlates significantly with DAS-ESR and DAS-CRP. It does not correlate independently with changes in inflammatory parameters ESR and CRP. PPT in conjuncture with DAS could be useful in routine clinical practice to measure the pain as well disease activity, in RA patients.