760 SECOND MORNING URINE METHOD IS MORE ACCURATE THAN THE CASUAL URINE METHOD FOR ESTIMATING DAILY SALT INTAKE IN PATIENTS WITH HYPERTENSION BY ANALYSES USING SECOND MORNING URINE SAMPLES

Purpose: The second morning urine (SMU) method developed by Kawasaki is reliable and convenient for estimating the daily salt intake. On the other hand, Tanaka have developed more convenient method named as casual urine (CU) method in which a urine sample can be collected during the daytime. However, it remains unknown how reliable the CU method is. Using second morning urine samples, we compared the CU and SMU methods for estimating daily salt intake in relation to the 24-h collection method. Methods: Data were obtained from three previously reported studies (A, B, C), in which we evaluated the daily salt intake by the SUM method. Study A was done in 1,315 outpatients without restriction of their salt intake. In study B, 100 inpatients were given a daily salt intake of 7 g. In study C, 22 inpatients received a daily salt intake of 18 g for a week, followed by a daily salt intake of 8 g for another week. Main outcomes: The estimated salt intake was lower with the CU method than the SMU method in outpatients (study A). In inpatients with a daily salt intake of 7 g (study B), 8 g (study C), or 18 g (study C), the CU method was applied to SMU specimens. It underestimated, salt intake compared with the 24-h collection method, while the SMU method and 24UC method gave similar results. Conclusions: The CU equation underestimated salt intake when using urine collected during the morning, while the SMU equation gave accurate results.