Thromboxane B2 and beta 2-microglobulin as early indicators of renal allograft rejection.

In a prospective study the diagnostic value of urinary thromboxane B2 (TXB2) and beta 2-microglobulin (beta MG) in renal allograft rejection was studied in 34 patients after transplantation. Twenty-four episodes of rejection were diagnosed by clinical symptoms. The clinical diagnosis of rejection was confirmed by an increase of urinary TXB2 in 21 (88%) cases. The augmented renal excretion of TXB2 proceded the clinical signs of rejection for 2.0 +/- 0.75 days. The symptoms in the remaining three (12%) cases of supposed allograft rejection without increased urinary TXB2 were caused by non-immunological events (urinary tract infection, acute tubular necrosis). No elevated TXB2 excretion was observed during urinary tract infection, sepsis, and acute tubular necrosis whereas urinary beta MG increased during these events as during transplant rejection. Urinary TXB2 was found to be an early, specific, and sensitive marker of renal allograft rejection with greater reliability than beta MG excretion or clinical signs of rejection.