‘Hot’ joints may predict RA joint damage




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.


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.

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