Estimated excretion and clearance of uric acid as optimal surrogate indices for daily urinary uric acid excretion

Abstract

Objectives Daily uric acid excretion is an essential index for patients with gout/hyperuricemias. We identified alternative indices most correlated with 24-hour uric acid clearance (Cua 24h) and 24-hour uric acid excretion (Eua 24h) using data from the reference interval of urinary clearance and excretion of urate study. Methods The subjects were indoor workers aged 20 to 65 who met the Clinical and Laboratory Standards Institute Guidelines C28-A3c. Alternative indices using spot urine were urine uric acid creatinine ratio, uric acid clearance - creatinine clearance ratio (Cua/Ccr), uric acid excretion - creatinine clearance ratio (Eua/Ccr), estimated uric acid clearance (eCua), and estimated uric acid excretion (eEua). eCua and eEua are the values obtained by multiplying Cua/Ccr and Eua/Ccr by the estimated glomerular filtration rate. Results The final number of subjects analyzed was 739. Among the indices using spot urine, eCua and eEua showed the highest correlation with Cua 24h and Eua 24h, respectively. Compared with Cua 60min and Eua 60min obtained from 60-minute urine collection, eCua and eEua showed lower root means squared error, lower bias, and significantly higher accuracy of within 30% and within 15%. Conclusions The newly proposed eCua and eEua may be appropriate from a practical perspective.