A critical analysis of serum and urine interleukin-2 receptor assays in renal allograft recipients.

A component of the interleukin 2 receptor (IL-2R) is released in soluble form during T cell activation and can be detected in the blood during acute renal allograft rejection. This study evaluates the diagnostic utility of a sandwich enzyme immunoassay test for serum and urine IL-2R in renal allograft recipients. A rise in serum IL-2R during the week prior to the clinical diagnosis of rejection correlated better with rejection than did isolated serum IL-2R levels or urine values. For the diagnosis of acute rejection, a rise in serum IL-2R (sensitivity 73%, specificity 87%) was comparable in overall test performance to a rise in serum creatinine (sensitivity 70%, specificity 84%). Overall, the two tests had equivalent receiver operating characteristic curves. Because the etiology of false positives in creatinine and IL-2R assays differed (primarily cyclosporine toxicity and infection, respectively), the predictive value of the combined tests was superior to either alone.