Measurement of joint inflammation in rheumatoid arthritis with indium-111 chloride.

Studies in the collagen and rabbit models of arthritis have indicated that indium-111 chloride (111InCl3) scintigraphy objectively measures synovial inflammation. Indium-111 chloride scans, with imaging three days after 19 MBq intravenous injection, were performed on 21 patients with definite or classical rheumatoid arthritis (RA), all of whom were functional class II. Standard clinical indices of disease activity were recorded at the time of imaging by the same investigator, who was unaware of the results of joint scans. In addition, eight patients with severe osteoarthritis, four of whom were considered to need hip or knee joint replacement, were similarly scanned. In each patient 16 joints were graded as 0 to 5, based on increasing degrees of 111InCl3 uptake, by a single investigator blinded to the patient's diagnosis and clinical status. In the group with RA significant correlations were observed between individual joint uptake on scan and peripheral joints with swelling, joints reported to be painful, and joints with any abnormality on physical examination. In the group with osteoarthritis joints positive on scan correlated with the presence of pain. A total scan score (sum of individual joint scores) was calculated for each patient. In the patients with RA values ranged from 0 to 42 with a mean (SEM) of 20.7 (2.7) and correlated with the number of swollen joints and decreasing grip strength. In the group with osteoarthritis the mean total scan score (9.2 (1.5), range 3-14) was significantly lower than in the patients with RA. These data show that 111InCl3 scanning can measure joint involvement by RA.