Determination of uric acid in scalp hair for non-invasive evaluation of uricemic controls in hyperuricemia.

The uric acid concentration in blood has been widely accepted as a diagnostic indicator of hyperuricemia and gout, and its assay method is well established. In the present study, we developed a simple and rapid method for the determination of uric acid in hair, which can be obtained non-invasively. The concentration (nmol/mg hair) of uric acid extracted from 10-20 mg hair with 0.1 M potassium hydroxide was determined by an enzymatic method using uricase. The concentration of uric acid (nmol/mg hair, mean+/-S.D.: 0.49+/-0.157, n=16) in hair from hyperuricemic patients was significantly higher than that (0.26+/-0.107, n=8) in healthy volunteers (p<0.01). The within-run and between-day precision (CVs) of the assay was 9.6-10.3% (n=10 each) and 11.6-16.3% (n=7 each), respectively. The concentration (nmol/mg hair, y) of uric acid in hair correlated well with that in serum (mg/l, x): y=0.09x-0.12 (r=0.75, Syx=0.122, n=23). Changes in the concentration of uric acid in the hair of antihyperuricemic drug-treated patient paralleled that in serum, suggesting that the concentration of uric acid in hair is a reliable indicator of the metabolic control in hyperuricemia.