A simple method of selecting gout patients for treatment with uricosuric agents, using spot urine and blood samples

OBJECTIVE: To develop a simple means of selecting gout patients for treatment with uricosuric agents. METHODS: In 124 gout patients, spot urine and blood were sampled before breakfast and after overnight fast (except water) on the day of 24 h urine collection. Spot urine uric acid/creatinine ratio (Ua/Cr mmol/mmol) and serum creatinine x Ua/Cr (Scr*Ua/Cr micromol/l) were calculated together with 24 h urinary uric acid excretion/body surface (24 Ua/S). The patients were then classified either below or above 2.84 mmol/m2/day for 24 Ua/S. RESULTS: Classifications based on spot urine Ua/Cr (cut off value set at 0.34), spot urine Scr*Ua/Cr (cut off value set at 28.1), and a combination of spot urine Ua/Cr and Scr*Ua/Cr were found to be not significantly different in diagnostic accuracy for the detection of patients with 24 Ua/S below 2.84 mmol/m2 (77%, 81%, and 81%, respectively) and sensitivity (80%, 83%, and 76%, respectively). However, specificity by a combination of spot urine Ua/Cr, and spot urine Scr*Ua/Cr was higher than by spot urine Ua/Cr alone (91% vs 74%, P < 0.05), although the specificity was not significantly different between a combination and spot urine Scr*Ua/Cr alone (91% vs 78%) or between spot urine Ua/Cr and spot urine Scr*Ua/Cr (74% vs 78%). CONCLUSION: A combination of spot urine Ua/Cr and spot urine Scr*Ua/Cr may be clinically useful in selecting gout patients with 24 Ua/S below 2.84 mmol/m2 for treatment with uricosuric agents without adverse effects.