Diagnostic Accuracy of Single Spot Urine for Detecting Renal Uric Acid Underexcretion in Men

BACKGROUND: The uric acid (UA) clearance test to evaluate the hyperuricemia phenotype requires a great deal of time. However, the utility of single spot urine is scarce. The study aimed to determine the diagnostic accuracy of single spot urine for predicting renal UA underexcretion (the decreased UA excretion) in men. METHODS: A total of 73 male participants aged 20 - 74 years with a UA level of 6.0 - 7.9 mg/dL were enrolled in the study. Renal UA underexcretion was defined as < 7.3 mL/min using the 60-min method. Urinary UA to creatinine ratio (UACR), fractional clearance of urate (FCU), and the Simkin index were calculated. A receiver operating characteristic (ROC) analysis was performed to compare the diagnostic utility of these parameters for predicting UA underexcretion. RESULTS: In the ROC analysis, the area under the curve values of the UACR, FCU, and the Simkin index for predicting UA underexcretion were 0.903 (95% confidence interval (CI): 0.830 - 0.976), 0.841 (95% CI: 0.749 - 0.933), and 0.779 (95% CI: 0.673 - 0.885), respectively. An optimal UACR cutoff of 0.460 (sensitivity 89.2%, specificity 80.6%, overall diagnostic accuracy 84.9%, positive predictive value 82.5%, and negative predictive value 87.9%) was identified. CONCLUSIONS: These results suggest that the UACR is a simple and efficient test with high sensitivity and specificity levels for predicting renal UA underexcretion in men.