Increased serum beta 2 microglobulin during rejection, cyclosporine-induced nephrotoxicity, and cytomegalovirus infection in renal transplant recipients.

In 83 renal transplant recipients, serum beta 2 microglobulin (beta 2m) levels were significantly elevated during pretransplant uremia, rejection, cyclosporine-induced nephrotoxicity, and infections. In patients with normal serum creatinine, 74% had elevated serum beta 2m levels. None of the cyclosporine-treated patients had normal levels of beta 2m. Patients with stable renal allograft function receiving cyclosporine showed significantly higher serum beta 2m (P less than 0.001) and serum creatinine (P less than 0.01) levels than azathioprine treated patients. Patients with an irreversible rejection showed significantly higher serum concentrations of beta 2m than patients experiencing a reversible rejection (P less than 0.001). During cytomegalovirus (CMV) infection the serum beta 2m levels were elevated compared with other infections (P less than 0.001), while the serum creatinine was not. However, infected patients had higher serum levels of beta 2m and creatinine than patients with stable renal allograft function (P less than 0.001). Serum beta 2m may therefore be useful in the early diagnosis of CMV infection. To conclude, serum beta 2m levels cannot distinguish between rejection, cyclosporine nephrotoxicity, or infection.