Disease activity indexes in rheumatoid arthritis; a prospective, comparative study with thermography

There are many difficulties associated with the assessment of disease activity in rheumatoid arthritis. Infrared thermography has been used to quantify joint inflammation. The heat distribution index (HDI) is reproducible, sensitive, quantifiable, and not subject to circadian variation or interobserver error. In this study the HDIs for both elbows, wrists, knees, and ankles were summated and compared with other parameters of disease activity. There were 167 sets of observations in 20 patients with classical, seropositive, rheumatoid arthritis followed up over 12 months. There was a significant correlation (p less than 0.001) for thermography with the Ritchie articular index, Mallya score, grip strength, morning stiffness, erythrocyte sedimentation rate, and pain score. Significant correlations (p less than 0.05) for thermography with these parameters were found in individual patients. The summated HDI is a suitable, objective method for the assessment of response to therapy in patients with rheumatoid arthritis.