Because primary aldosteronism is not uncommon, specifically treatable and in some cases curable, and carries higher risks for cardiovascular morbidity and mortality than essential hypertension, screening hypertensive patients for its presence by measuring aldosterone to renin ratio (ARR) is increasingly common. A significantly higher false-positive ARR rate for women than men, resulting in unnecessary suppression tests has previously been reported. Using a new, highly accurate aldosterone assay and both of the currently widely used renin assays, ARR was measured in 19 normal, ovulating women at three time points in the menstrual cycle and compared with single measurements in 21 normal males of similar age. ARRs in males were possibly too well down in the current normal range. Although normotensive and normokalemic, two women had raised ARRs in the luteal phase but only when direct renin concentration (DRC) was used. Their DRC levels were low at all sampling times [despite midrange plasma renin activity levels], whereas their progesterone and aldosterone levels were highest for the group. Saline suppression testing, performed in one of them, showed normal aldosterone suppressibility. False-positive ARRs in normal women during the luteal phase only when DRC is used may explain the higher incidence of false-positive ARRs in hypertensive women than men and suggest the following: 1) plasma renin activity is preferable to DRC in determination of ARR and 2) new reference ranges for ARR that take into account gender and sex hormone levels are required.
