Masahiko Owada

Effectiveness of a spot urine method in evaluating daily salt intake in hypertensive patients taking oral antihypertensive drugs

Kawasaki et al. developed a spot urine method (SUM) for evaluating daily salt intake using one pre-breakfast sample obtained after initial voiding upon arising. Their subjects were healthy persons who were not taking any regular medications. To determine whether SUM can be successfully used for patients taking antihypertensive drugs, we estimated daily salt intake in 73 hypertensive patients by SUM and by a food consumption method (FCM) when they were at home, and also by SUM in the hospital with a defined intake of 7 g of sodium chloride (NaCl). Forty-one patients took oral antihypertensive medications once daily, while 32 patients took none. Mean daily salt intakes by SUM during admission were 7–8 g of NaCl in both groups (95% confidence intervals: 5.0–10.6 g in the medication group; 5.2–11.1 g in the no-medication group), which corresponded well to the diet. In contrast, ambulatory daily salt intake by SUM varied widely (95% confidence intervals: 5.5–20.7 g in the medication group; 7.6–22.8 g in the no-medication group). However, the daily salt intakes determined by SUM and FCM correlated significantly with each other in the medication group (r=0.69, p<0.01) and the no-medication group (r=0.66, p<0.01). SUM is therefore a reliable method for evaluating daily salt intake in patients taking antihypertensive medication as well as unmedicated patients.

Effect of age on renal functional and orthostatic vascular response in healthy men.

1. Few studies have been reported concerning the effect of ageing on renal functional and vascular responses to various stresses during ordinary life. In the present study, we examined the effect of age on changes in renal sodium handling and renal vascular resistance (RVR) in response to standing from a supine position in subjects with normal renal function.

Second morning urine method is superior to the casual urine method for estimating daily salt intake in patients with hypertension

The accuracy of the casual urine (CU) method for estimating daily salt intake was compared with the second morning urine (SMU) method and with 24-h urine collection (24UC) method as the gold standard. Data were obtained from three previously reported studies, in which we evaluated the daily salt intake by the SMU method. Using SMU samples from 1315 outpatients, the estimated salt intake was lower with the CU method than the SMU method. In inpatients with a daily salt intake of 7, 8 or 18 g, the CU method was applied to SMU specimens. It underestimated salt intake compared with the 24-h collection method whereas the SMU method and 24UC method gave similar results. In the present study, 24UC was done and then urine was collected at 0800, 1100, 1400, 1700 and 1900 hours, with a daily salt intake of 6 g in 8 inpatients, 10 g in 11 inpatients or 15 g in 5 inpatients. In comparison with the 24UC method, the CU method underestimated a high salt intake (15 g) when morning specimens were used and overestimated a low salt intake (6 g) when afternoon specimens were used. The correlation between the CU method and 24UC method was weaker (R=0.57) than that between the SMU method and 24UC method (R=0.85). In conclusion, the CU method is heavily influenced by the timing of urine collection and by the actual daily salt intake, so the SMU method provides a better estimate of individual salt intake.

The influence of posture on the estimation of daily salt intake by the second morning urine method

The second morning urine (SMU) method was developed to evaluate daily salt intake, but the posture that should be adopted until the SMU collection remains unclear. This study investigated the influence of posture in hypertensive patients who underwent this test. The subjects were 100 patients who could collect 24-h urine samples correctly and were on a diet containing 7 g of salt per day. Their daily salt intake was estimated for three consecutive days in the recumbent, sitting, and sitting and standing positions (one posture each day). Estimated salt intake in the recumbent position (10.9±2.4 g day−1) was higher than in the sitting position (7.5±2.0 g day−1) and the sitting and standing position (6.3±1.7 g day−1). The salt intake estimated in the sitting and standing position was similar to that obtained by 24-h urine collection (6.3±1.6 g day−1) and was significantly (r=0.44, P<0.05) correlated with the 24-h urine value. The actual difference in estimated salt intake between the two methods was 0.0±1.7 g day−1. There were no significant differences in estimated salt intake between the two methods in patients taking different classes of antihypertensive drugs. In conclusion, adopting the sitting and standing position until the SMU collection is important for the correct estimation of daily salt intake, and this method could replace the 24-h collection method because of its convenience, especially in outpatients.

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.

1045 CASUAL URINE METHOD FOR ESTIMATING DAILY SALT INTAKE IS INFLUENCED BY THE TIMING OF URINE COLLECTION AND THE ACTUAL DAILY SALT INTAKE IN PATIENTS WITH HYPERTENSION

Purpose: On the basis of the second morning urine (SMU) method by Kawasaki for estimating the daily salt intake, Tanaka have developed a casual urine (CU) method in which a urine sample can be collected during the daytime. However, it remains unknown concerning the reliability of the CU method. Therefore, we examined the effect of urine collection time on CU methods in relation to the 24-h collection method. Methods: Daily salt intake was set at 6 g (n = 8), 10 g (n = 11), or 15 g (n = 5) per day during admission. One week after admission, urine was collected for two days. On Day 1, after voiding at 6:00, urine was collected for 24 hours. On Day 2, urine was collected at 8:00, 11:00, 14:00, 17:00, and 19:00. Salt intake was estimated by the CU equation. Furthermore, salt intake was estimated by both the CU, and SMU equations using the urine sample obtained at 8:00 (second morning urine). Main outcomes: In comparison with the 24UC method, the CU method underestimated a high salt intake (15 g) when morning specimens were used and overestimated a low salt intake (6 g) when afternoon specimens were used. The correlation between the CU method and 24UC method was weaker (R = 0.57) than that between the SMU method and 24UC method (R = 0.85). Conclusion: the CU method is heavily influenced by the timing of urine collection and by the actual daily salt intake, so the SMU method provides a better estimate of individual salt intake.