Table 3.

Casual and 24-h urinary Na/K ratio, correlation coefficients and agreement in individuals, overall (n =10 065) and by demographic stratum

Population sample		Casual urine Na/K ratio		24-h urine Na/K ratio		Correlation coefficients between casual and 24-h urine Na/K ratio	Agreement with Bland–Altman plot
	n	Mean	SD	Mean	SD		Bias	95% of difference
Overall	10 065	2.85	2.15	3.24	1.90	0.69	0.40	6.32
Individual men	5039	2.87	2.11	3.29	1.92	0.70	0.42	6.21
Individual women	5026	2.83	2.18	3.20	1.89	0.68	0.37	6.42
Individuals aged 20–24	1137	2.93	2.39	3.30	2.03	0.72	0.37	6.60
Individuals aged 25–34	2662	2.97	2.21	3.34	1.94	0.68	0.37	6.56
Individuals aged 35–44	2533	2.78	2.09	3.15	1.86	0.69	0.38	6.22
Individuals aged 45–54	2564	2.86	2.08	3.25	1.84	0.69	0.40	6.10
Individuals aged 55–59	1169	2.66	1.97	3.17	1.93	0.68	0.51	6.17
White individuals	5853	2.51	1.56	2.84	1.20	0.58	0.33	5.15
Black individuals	980	2.89	2.10	3.57	2.16	0.47	0.69	8.57
Native American individuals	561	1.10	2.13	1.13	1.79	0.81	0.04	4.91
Asian-Indian individuals	406	3.95	2.47	4.17	1.84	0.70	0.22	6.90
East Asian individuals	1578	4.61	2.79	5.26	2.16	0.64	0.65	8.51
Individuals of other ethnicities (others)	687	2.48	1.93	2.76	1.92	0.70	0.31	5.85
Individuals taking neither anti-hypertensive medications nor potassium	7629	2.92	2.19	3.30	1.94	0.72	0.38	6.16
Individuals taking anti-hypertensive medications or potassium	2436	2.63	1.99	3.08	1.76	0.58	0.45	6.80

Na, sodium; K, potassium; SD, standard deviation. Bias is mean value of the difference of Na/K ratio between 24-h urine collection and casual urine as defined in the Bland–Altman method. 95% of difference is width between upper limit and lower limit in the Bland–Altman plot. Anti-hypertensive medications include potassium sparing diuretics, other diuretics and other anti-hypertensive drugs affecting BP. East Asian individuals are defined as Chinese, Japanese and Korean individuals. Details of the definition of ethnic groups are defined.³³