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

Abstract

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.

Assessment of Disease Activity by Infrared Thermography in Patients with Rheumatoid Arthritis: A Comparative Cross-Sectional Study of Thermographic, Clinical and Ultrasound Assessments

“…In 2018, Jones et al (24) compared thermal imaging of the hand joints of patients with RA to those of healthy volunteers. Their patients' characteristics were similar to ours.…”

“…Thermographic analysis of joint temperature was not associated with clinical measures of disease activity. The calibration of their camera, the computer software, and the temperature assessment were not speci ed (24). The authors suggest that the clinical examination may lack sensitivity and that it would be interesting to compare it with US assessment.…”

“…Some studies have already assessed RA activity, in particular in small joints, by infrared thermography through the use of miniaturized thermal cameras, but with discordant results (22,24). No study has compared thermography to ultrasound to date.…”

Pre‐Clinical Testing of Microwave Radiometer and a Pilot Study on the Screening Inflammation of Knee Joints

“…Medical IR thermography maps the skin surface temperature and thermal activity in the proximity of the skin surface. Due to the shallow penetration in IR spectrum, high resolution IR cameras (10−50 mK) are used for medical imaging [Lasanen et al, ; Jones et al, ]. As a result, IR thermography is susceptible to background noise, has substantial variation in image interpretation across operators, and requires sophisticated image analysis software dedicated to the anatomy [Spalding et al, ].…”

“…The presence of soft tissue between the skin and knee joint that affected heat conduction to the skin surface was cited as the reason for the inability to detect the inflamed knee joints using IR thermography. Another recent study on IR thermal imaging of inflammatory arthritis of the hand also did not show significant temperature rise at the inflamed joints [Jones et al, ]. An alternative thermal imaging technique for detection of deep tissue inflammation is medical microwave radiometry.…”