The measurement of pain pressure threshold in patients with rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic systemic disease with characteristic diffuse pain that causes disability in patients. Although pain pressure threshold (PPT) has been studied widely in fibromyalgic patients, PPT studies in RA patients were inadequate. In this study the evaluation of PPT and it's relation with disease activity in patients with RA has been proposed. Thirty-two patients with RA (24 female, 8 male) and 34 healthy volunteers comprising of hospital staff and their relatives (22 female, 12 male) were included into the study. PPT measurements (kg/cm(2)) have been performed from 3 control and 18 tender points in both groups. For each subject number of tender points, a control point score (CPS) and a total myalgic score (TMS), obtained by algometer, have been calculated. Significantly lower values of TMS and CPS in the RA group were obtained with respect to the healthy controls (p < 0.001). Patients with RA had a greater number of tender points than the control subjects and most of them (78%) had more than 11 tender points TMS was negatively correlated with the ESR and CRP values (r = -0.35, p < 0.05 and r = -0.37, p < 0.001, respectively) and there was a moderate significant correlation between the TMS and Ritchie Articular Index (RAI) (r = -0.58, p < 0.001). There was no significant correlation between CPS and ESR and CRP values whereas a negative correlation was found between CPS and RAI(r = -0.60, p < 0.001). A moderate significant correlation was also determined between the RAI and the tender point count (r = 0.43, p < 0.05). In conclusion, PPT in patients with RA has been determined as lower than in healthy age and sex matched control subjects and established to be related to the disease activity. Furthermore significantly lower CPS and increased tender point counts, that were well above 11, make us consider that there may exist a fibromyalgic component acting with RA in most of the patients.