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

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