Using Dermal Temperature to Identify Rheumatoid Arthritis Patients With Radiologic Progressive Disease in Less Than One Minute

OBJECTIVE: To explore development of a screening test for rheumatoid arthritis (RA) patients most likely to develop radiographic damage in the next year. The test is a simple, objective measurement of elevated dermal temperature over an inflamed joint in this observational, prospective cohort study. METHODS: Seropositive RA patients were sequentially enrolled into cohorts with hot or cool joints, as determined by a dermal thermometer. Patients naive to biologic therapy were maintained on a stable dosage of methotrexate (20–25 mg/week). The hot‐joint cohort had a joint skin temperature greater than their body temperature on vital signs. Hand/wrist radiographs obtained at baseline and 1 year later were read and scored using modified Sharp/van der Heijde scores (SHS) by a single reader without sequence order or identifiers. RESULTS: Each cohort consisted of 104 patients enrolled into observation between 2009 and 2014. Patients in the cohort with hot joints had a mean ± SD joint temperature of 1.06 ± 0.69°F above central body temperature and a nearly 4‐fold higher risk of new radiographic damage than those with cool joints (SHS score 8.7 ± 6.2 versus 2.5 ± 1.4; P < 0.001). Sensitivity and specificity for joint temperature to predict radiographic damage in the next year were 92% and 78%, respectively, in the hot‐joint cohort. As expected, this cohort at baseline was younger, had more recent onset RA, and had higher Westergren erythrocyte sedimentation rate levels than the cool‐joint cohort (P < 0.001 for each). CONCLUSION: Dermal joint temperature may become a screening test to quickly and accurately identify individual RA patients at high risk for radiographic damage and those who may benefit most from biologic therapy.