SERUM INTERLEUKIN-2 RECEPTOR FOR THE EARLY DIAGNOSIS OF RHEUMATOID-ARTHRITIS

The value of measuring soluble interleukin-2 receptor (sIL-2R) in the sera of patients with joint pain as a predicting parameter for the fut ure development of rheumatoid arthritis (RA) was examined. sIL-2R was measured by the ELISA method. Sixty-four patients with joint pain (sus pected RA: sus-RA) but no bone or joint destruction were enrolled over 2 years and 47 were selected for the study. Eleven patients whose dia gnosis was sus-RA after a year of observation were successively follow ed-up for 5 years. Two-thirds of the patients whose sIL-2R levels were higher than those of normal healthy adults (< 82 pmol/l; mean +2SD) d eveloped RA within a year. On the other hand, one-quarter of the patie nts with normal levels of sIL-2R also developed RA within a year. The presence of two or three of the following three items in patients with joint pain without any bone and joint destruction was thus indicated to be useful for the early diagnosis of RA: elevated CRP level (greate r than or equal to 1.0 mg/dl), positive rheumatoid factor (RF) (greate r than or equal to 30 IU/ml) and an elevated sIL-2R level (greater tha n or equal to 100 pmol/l). Sensitivity and specificity were 72.7% and 96.0%, respectively. The probability of development of RA is expressed as P = 1/[1 + exp(2.673 - 0.01784 x sIL-2R - 0.4398 x CRP - 0.004835 x RF)], with R-2 = 0.3083 and p<0.0005. On the other hand, the sIL-2R levels did not correlate with any future bone or joint changes within a year of observation. The above criteria may therefore hopefully just ify the early treatment of patients with joint pain using drugs that c an modify the patients' immune function. However, the validity of thes e criteria still need to be examined more thoroughly in the future.