Researchers at Staffordshire University have found that palm and finger temperature increase significantly in patients with rheumatoid arthritis (RA), meaning thermal imaging could be used to diagnose the condition in the future.

Two rheumatologists examined 31 RA patients and 51 healthy control patients. A subset of the participants underwent a diagnostic ultrasonography to ensure they had no active signs of synovitis – swelling of the joints originating in the synovial membrane – in their hands or wrists.

Using a Flir T630 thermal camera, the researchers found that individuals with higher palm and finger temperatures were more likely to have RA, with or without active synovitis.

Staffordshire University visiting fellow and lead author of the study Dr Alfed Gatt said: “The results of our study show that the two probability curves intersect at 31.5 for palm temperatures, indicating that individuals whose palm temperature is less than 31.5% are more likely to be healthy, while those persons whose palm temperature is less than 31.5 are more likely to have rheumatoid arthritis. Similarly, for finger temperatures, the two probability curves intersect at 30.3%.

“While ultrasonography had not detected any significant changes in our study population, thermography flagged a possible ongoing disease process by reporting these higher temperatures.”

The researchers believe the temperature difference may be the result of underlying subclinical disease activity, or that the original inflammatory process of RA could cause irreversible thermal changes which persist even when symptoms of the condition resolve.

Gatt said: “Thermal imaging is an emerging technology within medicine and has the potential to become an important clinical tool as disease processes can vary the magnitude and pattern of emitted heat in a person with Rheumatoid Arthritis.”

RA affects over 400,000 adults in the UK, and can lead to deformity, disability and cardiovascular problems. Early detection of synovitis can make a significant difference in terms of disease control, but this can be very difficult to diagnose.