Limited value of uric acid to creatinine ratios in estimating uric acid excretion.

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The value of the uric acid to creatinine ratio and the uric acid to creatinine clearance ratio in predicting 24 -hour urinary uric acid excretion was assessed in 49 patients with normal enzyme activity and 22 patients with purine enzyme deficiencies . A 24 -hour urinary uric acid to creatinine ratio greater than 0 .75 was found in six of nine patients with a partial deficiency of hypoxanthine-guanine phosphoribosyltransferase and in all patients with Lesch-Nyhan syndrome . A ratio of less than 0 .10 suggested xanthinuria or severe purine nucleoside phosphorylase deficiency . Neither ratio calculated from 2 -hour timed collections of the 24 -hour specimen showed a high correlation with 24 -hour urine uric acid excretion in patients with normal enzyme activity , perhaps because of a diurnal variation in urinary uric acid excretion . The spot-urine uric acid to creatinine ratio does not accurately predict the 24 -hour urine uric acid excretion in patients with normal enzyme activity .