Recording the temperature of skin over an inflamed joint may identify rheumatoid arthritis patients at high risk of joint damage, an exploratory study suggested.
Dermal joint temperature could become a screening test to “quickly and accurately” identify individual RA patients at high risk for radiographic damage and those who may benefit from biologic therapy, said Dr. Maria Greenwald, a rheumatologist in group practice in Palm Desert, Calif., and her colleagues.
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During 2009-2014, the investigators enrolled seropositive RA patients who were on stable doses of methotrexate (20-25 mg/wk) for the past 3 months and did not use biologics or other disease-modifying antirheumatic drugs. It took 9 months to enroll 104 patients with cool joints and 42 months to enroll 104 patients with hot joints, suggesting “that at a single office visit, RA patients on methotrexate are five times more likely to have cool joints than hot joints,” the researchers reported.
The results showed that patients in the hot-joint cohort had a nearly fourfold higher risk of x-ray damage at 1-year follow-up, compared with those with cool joints (change in modified van der Heijde total Sharp score [mTSS]: 8.7 vs. 2.5; P less than .001). Patients with hot joints had an average joint temperature exceeding central forehead body temperature by 1.1° F, whereas those with cool joints had an average joint temperature of 4.3° F below central forehead body temperature.
In the cohort of patients with hot joints, 74% had clear x-ray evidence of new joint damage (mTSS of 5 or greater), compared with 7% of cold-joint cohort patients at 1-year follow-up. Joint temperature at the hand or wrist predicted x-ray damage in the next year with 92% sensitivity and 78% specificity(Arthritis Care Res. 2015 Dec 14. doi: 10.1002/acr.22813).
Patients in the hot-joint cohort were younger, had more recent onset of RA, and had a significantly higher Westergren erythrocyte sedimentation rate than patients in the cool-joint cohort, the investigators noted.
They suggested a future study might define a hot-joint cohort as RA patients with a joint that measures over a set point such as 98° F. “Such a cutoff would make assessment very simple and would maintain the specificity and sensitivity of the model,” they said.
No conflicts of interest were disclosed.