Screening for primary aldosteronism: hypokalemia in hypertensive patients.

A serum potassium determination is usually recommended for new hypertensive patients as a screening test for primary aldosteronism and as a baseline for drug therapy. Since hypokalemia is not specific for aldosteronism, the authors assessed its use and limitations as a screening test in nine reported studies of 303 patients with aldosterone-producing adenomas (n = 252) or adrenal hyperplasia (n = 51). The optimal potassium cutoff level and the predictive ability of hypokalemia to detect aldosteronism were analyzed in a primary care setting with different diseases, test characteristics, and prevalences. Optimal screening for primary aldosteronism occurred at serum potassium less than 3.2 mEq/l in a primary care, low-prevalence population, and at higher potassium levels in higher-prevalence populations. Other screening tests, such as urinary aldosterone levels and plasma renin activity, showed lower individual test performance characteristics, but when combined were similar in performance to serum potassium measurement.