[Feasibility evaluation of estimating the 24-hour urinary sodium excretion in Chinese population with three spot...

Objective: To evaluate the feasibility of three spot urine methods (Kawasaki, INTERSALT and Tanaka) for estimating the 24 h urinary sodium excretion in the Chinese population. Methods: In 2017, 1 499 participants aged 18 to 69 years old were selected from Yiwu City, Haining City, Taishun County, Yinzhou District of Ningbo City and Liandu District of Lishui City of Zhejiang Province by using the multistage random sampling method. Sociodemographic information of the subjects was collected with questionnaires and physical measurements were performed. 24 h urine was collected and urinary volume was recorded. The concentrations of urinary sodium, potassium and creatinine were also measured. Kawasaki, INTERSALT and Tanaka spot urine methods were applied to estimate the 24 h urinary sodium excretion and compared with actual values among 1 426 participants who passed urine integrity test. Results: The age of participants was (46.71±14.04) years old, including 700 males, accounting for 49.1%. The actual value of 24 h urinary sodium excretion was (167.10±74.70) mmol, but Kawasaki method overestimated it as (184.61±57.10) mmol, and INTERSALT and Tanaka methods underestimated it as(134.62±39.21) and (143.20±35.66) mmol. Estimated difference (95%CI) (mmol) from small to large was Kawasaki method [17.51 (13.54, 21.47)], Tanaka method [-23.90 (-27.60, -20.20)] and INTERSALT method [-32.48 (-36.29, -28.67)]. With the increase of 24 h sodium intake, all estimation methods changed from the overestimation to underestimation. In those with 24 h sodium intake <9.0 g, the estimated difference (95%CI) of the INTERSALT method was the smallest as 43.15 (37.73, 48.57) and 1.26 (-2.10, 4.63) mmol for <6.0 and 6.0-8.9 g groups, respectively. In those with 24 h sodium intake≥9.0 g, the Kawasaki method had the smallest estimated difference (95%CI) as -12.50 (-18.14, -6.86) and -53.73 (-61.25, -46.22) for 9.0-11.9 g and ≥ 12.0 g group, respectively. The consistency analysis of the Bland-Altman method showed that the Kawasaki method had the best consistency with actual measured value and it had the least number of points outside the range (69 points accounting for 4.84%). Conclusion: Among the three spot urine methods, the Kawasaki method has better applicability in predicting the excretion of 24 h urine sodium in the Chinese population.