Comparison of urinary N-acetyl-beta-D-glucosaminidase and urinary fibrin degradation products for diagnosis of rejection after renal transplantation.

A comparison was made of two established tests to see which was the better indicator of rejection after renal transplantation. Daily urine samples were assayed for excretion of N-acetyl-beta-D-glucosaminidase (NAG) and fibrin degradation products (FDP). Twenty-five rejection episodes were studied in 19 patients. Both indicators tended to move in parallel. NAG was more often elevated in rejection, namely in 96% of rejection episodes as against 76% for FDP, FDP had the advantage of fewer false positive results and when it correctly indicated rejection its increase above the baseline was relatively greater than for NAG, NAG and FDP can both provide early warning of rejection. NAG is preferred for its ease of assay. Assays are performed daily and are of practical value in clinical management. The results of assays must be interpreted in conjunction with all relevant information.