Comparison of measuring methods of urinary uric acid excretion

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Objective: To explore the consistency of urinary uric acid excretion at different time points with 24-hour urine as the gold standard.
Methods: We analyzed 118 inpatients from the department of endocrinology in Zhongshan Hospital from June to October, 2014. Urina sanguinis, 12-hour urine, 4-hour urine, 8-hour urine and 24-hour urine were collected and uric volume, uric acid concentration and creatinine concentration were tested for each urine sample. The consistency and correlation of urinary uric acid excretion in different time were analyzed by Pearson and partial relevance together with Intra-class Correlation Coefficient (ICC) and Bland-Altman tests.
Results: With uric acid excretion of 24-hour urine as gold standard, ICC test showed general consistency in 12-hour urine (ICC=0.56, P<0.001), and no consistency in 4-hour and 8-hour urine, respectively (P>0.05). Bland-Altman test showed weak consistency in those three indexes. With uric acid clearance of 24-hour urine as the gold standard, ICC test showed general consistency in 12-hour and 8-hour urine, respectively (ICC=0.40~0.75, P<0.001), and weak consistency in 4-hour urine (ICC=0.34, P=0.014). Bland-Altman test showed weak consistency in those three indexes. With fractional excretion of uric acid (FEUA) of 24-hour urine as the gold standard, ICC test showed strong consistency in 12-hour urine, 8-hour urine and urina sanguinis, respectively (ICC>0.75, P<0.05), with weak consistency in 4-hour urine (ICC=0.35, P=0.012). Bland-Altman test showed good consistency in 8-hour urine and urina sanguinis, respectively.
Conclusion: There were strong consistencies in FEUA of 8-hour urine, urina sanguinis and 24-hour urine, respectively, which can be substitutes of FEUA of 24-hour urine.