In 221 patients with primary gout, we studied urinary N-acetyl-β-D-glucosaminidase (NAG) as an index of tubular injury with respect to associated disorders such as nephropathy, hypertension and diabetes mellitus. Gouty patients had elevated urinary NAG excretion, compared with age-matched controls. Urinary NAG was not correlated with β2-microglobulin excretion. The elevation of NAG was highest in gouty patients with uncontrolled hyperuricemia. Serial measurements of NAG showed that gouty patients with uncontrolled hyperuricemia of more than 10 years duration had increased urinary NAG excretion, compared with well controlled patients. However, aged gouty patients did not have higher urinary NAG excretion. Gouty patients with nephropathy, hypertension or diabetes mellitus showed markedly elevated NAG excretion.
Thus, urinary NAG excretion appears to be a useful index of early tubular damage or nephropathy caused by disorders associated with gout.
