Urinary Sodium/Potassium Ratio Screens for Hyperaldosteronism in Hypertensive Men

Among individuals with hypertension, the prevalence of secondary hypertension has been reported to be around 10%. More than half of individuals with secondary hypertension have associated hyperaldosteronism.

Hyperaldosteronism is a medical condition wherein too much aldosterone is produced by the adrenal glands, which can lead to lowered levels of potassium in the blood (hypokalemia) and increased hydrogen ion excretion (alkalosis).

A team of medical scientists led by those at Kyoto Prefectural University (Kyoto, Japan) hypothesized that the urinary sodium/potassium ratio (Na/K) could be used as a simple, low-cost method of screening for hyperaldosteronism among individuals with hypertension in primary care and health examination settings. They recruited hypertensive individuals aged 30-69 years old who were not taking any antihypertensive medications from among participants in health examinations. Overall, 160 participants (108 men and 52 women) with a mean age of 54.3 years were eligible for this study.

Urinary Sodium (Na) and potassium (K) were measured using second morning urine samples, and the plasma aldosterone concentration (PAC) was also measured. The assay kit used for the measurement of the PAC was the SPAC-S Aldosterone Kit (TFB, Inc. Tokyo, Japan). The team evaluated the association of the second morning urine Na/K ratio (SMU Na/K) with a high PAC, defined as ≥90th percentile (24.3 ng/dL), using receiver operating characteristic (ROC) curves.

The investigators reported that the area under the ROC curve for the relationship between SMU Na/K and high PAC was 0.77 (95% confidence interval [CI]: 0.59-0.95) in men and 0.64 (95% CI: 0.36-0.93) in women. In men, SMU Na/K values of less than 1.0 could detect hyperaldosteronism with a sensitivity of 45.5%, a specificity of 97.9%, a positive predictive value of 71.4%, and a negative predictive value of 94.1%.

The authors concluded that the use of the urinary Na/K ratio may be appropriate as a method of screening for hyperaldosteronism in hypertensive men. The urinary Na/K ratio in second morning urine was inversely associated with the PAC in hypertensive men but not in women. A low urinary Na/K ratio could be a surrogate marker for the detection of a high PAC in hypertensive men. The study was published on May 17, 2021 in the journal Hypertension Research.

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Kyoto Prefectural University
TFB Inc