High prevalence of primary aldosteronism in the Tayside hypertension clinic population

Primary aldosteronism (PA) was thought to be rare but recent evidence from Australia suggests that it may be more common. As this has important implic ations in terms of hypertension management, we undertook to screen for this treatable condition in our hypertension clinic. We obtained blood samples in sequential patients referred for assessment in our hypertension clinic i n Tayside for plasma renin activity (PRA) and aldosterone. The aldosterone to PRA ratio (ARR) was used as an initial screening test to identify potent ial patients with PA. Those patients with an elevated ratio (greater than o r equal to 750) were admitted for the salt loading and ftudrocortisone supp ression test. These patients also underwent adrenal CT scanning, and in sel ected patients, adrenal scintigraphy. Between May 1995 and January 1997 (21 months), we screened a total of 495 patients. ARR was available in 465 (93 .9%) patients. Out of that number, 77 (16.6%) had an elevated ratio of grea ter than or equal to 750, five of whom had an adrenal adenoma tone had prev ious adrenalectomy). Forty-five of these patients were admitted for the sal t loading and fludrocortisone suppression test with 41 positive test result s suggesting PA. One patient with a negative salt loading test result howev er had an adenoma proven on histology. A total of 43 cases of PA were ident ified, giving a minimum prevalence of 9.2% (43/465), Potentially the preval ence may be up to 15% assuming that the ARR has a sensitivity of 93% (42/45 ) in predicting PA, In conclusion, about one in 10 patients attending a hyp ertension clinic may have PA. This suggests that the prevalence of PA in Ta yside is as high as that in the Australian hypertensive population, and thi s is likely to be true elsewhere, with obvious important implications for h ypertension management.