Background Despite better disease control, RA patients still rate pain as a major burden. That pain in some cases persists without signs of inflammation of the joints may indicate, that central pain sensitization could play a major role in the generation of chronic pain in some RA patients (1). Pain assessment is part of several tools used to evaluate RA disease activity e.g. DAS28 score. When applying DAS28, RA patients scoring high on tender joint count and global health may be classified to have active RA, despite no signs of inflammation (2). Central sensitization may also in part explain the significant portion of RA patients not responding to biologics treatment.
Computerized Pneumatic Cuff Pressure Algometry (CPA) is a method for quantitative measurements of pain reactions and indications of central sensitization (3). Knowledge of contributing pain mechanisms in RA may be crucial, since interventions aimed at decreasing the inflammatory processes may not be sufficient in all patients.
Objectives To assess the degree of peripheral and central sensitization in women with active RA compared to healthy controls.
Methods 38 women with active RA (DAS28>2,6) and 38 healthy controls were included in the study. CPA measurements were carried out on the dominant arm and leg. Following variables were determined: Pain Detection Threshold (PDT), Pain Tolerance Threshold (PTT), and Pain Tolerance Limit (PTL). Following this, during 10 minutes constant pressure stimulation at intensity relative to the individual pain threshold, the pain intensity was continuously recorded using an electronic Visual Analogue Scale (VAS). From this the degree of temporal summation (TS) was estimated (10 min CPA test at 50% of PTT-PDT). An index was calculated: TS-index = log((VASend/VASmax)*(10/Tstim)*VASend) (5).
Results Women with active RA have a lower pain threshold and pain tolerance than healthy controls. The mean TS-index in RA patients was 0.95 (95%CI: 0.86 to 1.04) and 0.81 (95%CI: 0.74 to 0.89)in healthy controls. Mean Difference was 0.14 (95%CI: 0.02 to 0.26; p = 0.022).
Conclusions In active RA patients the TS index as measured by cuff algometry was on average increased, indicating signs of central pain sensitization. This type of pain may be of importance when considering treatment strategies.
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Disclosure of Interest None Declared
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