REDUCED RENAL-ALLOGRAFT SURVIVAL IS RELATED TO LOW URINARY N-ACETYL-BETA-D-GLUCOSAMINIDASE EXCRETION DURING THE FIRST POSTTRANSPLANT MONTH

The excretion of urinary N-acetyl-beta-D-glucosaminidase (NAG) was mea sured daily between day 7 and day 28 in 33 renal allograft recipients enjoying an entirely uncomplicated first postoperative month, Graft st atus was evaluated after 4 and 6 years and related to NAG excretion. A fter 4 years, 6 patients had experienced graft loss due to chronic rej ection, Posttransplant urinary NAG excretion in the group of patients with failing grafts was significantly lower (9.4+/-6.3 vs. 17.2+/-8.5 U/g urinary creatinine, P=0.036), Univariant analysis of recipient and donor characteristics revealed urinary NAG excretion to be the only p arameter significantly differing between the groups, After 6 years, a total of 8 patients had lost their grafts, The posttransplant urinary NAG excretion in this group was 10.8+/-6.2 U/g; in the 25 patients wit h functioning grafts NAG excretion was 17.4+/-8.8 U/g (P=0.084), A ver y low urinary NAG excretion (<7 U/g) was seen in 5 patients and associ ated with poor graft survival after 4 and 6 years (odds ratios 12.5 (1 .9-82.1) and 6.9 (1.1-44.8), respectively), Kaplan-Meier analysis show -ed a reduced graft survival in this subgroup (P=0.031), Receiver oper ating characteristics (ROC) analysis demonstrated an association betwe en low NAG excretion and graft survival rates both at 4 and 6 years (a rea under the ROC curve 0.799+/-0.115, P<0.05, and 0.747+/-0.104, P<0. 05, respectively), Cox proportional hazards analysis identified a low urinary NAG excretion as an independent prognostic risk factor. Urinar y NAG excretion was expressed as unit per gram of urinary creatinine; as the amount of NAG excreted depends on the graft mass, and the amoun t of urinary creatinine depends on the recipient body mass, a low NAG excretion (in terms of U/g urinary creatinine) could be a surrogate ma rker of an unfavorable low graft to body weight ratio, which, in turn, might be associated with a reduced graft survival.