Evaluating medical thermography for the detection of joint synovitis of hands and feet in people living with rheumatoid arthritis

Abstract

Aim: To determine whether infrared thermography could detect the presence of joint synovitis in the hands and feet of people living with Rheumatoid Arthritis. Methods: A single-centre, quantitative, prospective, non-experimental, observational, comparative study was conducted at the Rheumatology Department in Mater Dei Hospital. The sample (n=26) included 5 participants who had joint synovitis (used as controls) and 21 participants whose status of whether joint synovitis was present or absent was unknown. The consultant rheumatologist conducted the disease activity score (DAS-28) assessment and an ultrasound assessment of the hand and feet whilst, a state registered podiatrist performed the Ritchie Articular Index (RAI) and thermographic imaging assessment of the hands and feet. Results: The study findings highlighted a significant difference between the temperature readings and ultrasound readings (p<0.05) of hands and feet. In all the joints of participants (n=26), the temperature readings taken with the FLIR thermographic camera were higher when joint synovitis was present on ultrasound then the temperature readings when joint synovitis was absent on ultrasound. Additionally, through the regression models the temperature cut-off points between participants living with RA in remission and participants with active synovitis was established for the finger, palm, forefoot and midfoot and heel. Finally, amongst the participants whose RA status was unknown (n=21) the results of the chi-square test (p>0.05) showed no significant difference between the results obtained from the FLIR thermographic camera images and the diagnostic ultrasound demonstrating a perfect agreement in results between both tools as to whether joint synovitis was either present or absent. Conclusion: The study findings conclude that in all the joints of the hands and feet, the temperature readings taken with the FLIR thermographic camera were higher when joint synovitis was present on ultrasound compared to no presence of synovitis. This study has identified the temperature cut-off points of the finger, palm, forefoot and midfoot and heel for individuals with RA in remission and individuals with RA with active synovitis, thus these results have added to the body of knowledge the baseline temperatures of an individual with RA with joint synovitis of the hands and feet. Since readings obtained from the FLIR thermographic camera correlated with the results obtained from diagnostic ultrasound in the detection of joint synovitis in the hands and feet, the authors recommend routine screening in RA patients utilizing infrared thermography as an alternative measure to diagnostic ultrasound for the early detection if any, of joint synovitis to enable early referral and management of this condition . Further studies are warranted to further confirm results of this study.