Hot joints: myth or reality? A thermographic joint assessment of inflammatory arthritis patients

Rheumatoid arthritis is a common inflammatory disease that causes destruction of joints. Accurate recognition of active disease has significant implications in determining appropriate treatment; however, there is significant inter-rater variability in clinical joint assessment. This study aimed to assess the utility of thermographic imaging in the evaluation of inflammatory arthritis activity as an adjunct to clinical assessment. This was a cross-sectional study of 79 subjects recruited from the University of Alberta Outpatient Rheumatology clinic comparing the hand joints of 49 patients with rheumatoid arthritis (RA) diagnosed by American College of Rheumatology (ACR) criteria to 30 healthy volunteers. Convenience sampling of consecutive RA patients was undertaken. The effect of clinical assessment (HAQ and DAS-28) on joint temperature was evaluated using a linear mixed effect model. A thermography camera, FLIR T300 model, 30 Hz, was used to obtain both thermographic and digital images on subjects. Pearson's correlation coefficient was used to assess the correlation of clinical assessments and average joint temperature averaged over all joints. Thermographic analysis did not associate with clinical measures of disease activity. In RA patients, there was no statistically significant relationship between joint temperature and clinical assessment of disease activity including Health Assessment Questionnaire (coefficient estimate - 0.54, p = 0.056), swollen joints (coefficient estimate - 0.09, p = 0.238), or serologic markers of inflammation such as CRP (coefficient estimate - 0.006, p = 0.602) and ESR (coefficient estimate - 0.01, p = 0.503). Evaluation of disease activity requires a multifaceted approach that includes clinical assessment and appropriate imaging. There may be a role for thermography in assessment of larger joints; however, it does not appear to be an effective modality for the small joints of the hand.