Use of renal enzymes to evaluate nephrotoxicity in lithium treated patients.

N-acetyl-beta-glucosaminadase (NAG) is a renal enzyme which is an early, sensitive and reliable indicator of renal damage. NAG assays of midstream spot urines were not significantly different in a group of controls when compared to patients starting lithium for the first time, or to a group of patients who had been taking lithium for more than one year. However, a small number of lithium-treated patients may have evidence of renal damage, identifiable by NAG assay.