Is primary aldosteronism underdiagnosed in clinical practice?

1. Primary aldosteronism is a syndrome consisting of hypertension, suppressed renin activity or concentration and high aldosterone levels in plasma or urine. The main steps in diagnosis are the determination of renin and aldosterone levels, the demonstration of renin-aldosterone dissociation and discrimination between idiopathic hyperplasia and Conn's adenoma, with only Conn's adenoma amenable to surgery. 2. Patients with resistant hypertension and/or hypokalaemia should be screened for primary aldosteronism with simple, redundant hormonal tests. The aldosterone to renin ratio is a logical initial screening test, a high ratio demonstrating renin-aldosterone dissociation. Criteria for a high ratio should be determined in each laboratory. 3. In patients with documented primary aldosteronism, computed tomography scan and adrenal vein sampling help to distinguish between idiopathic hyperplasia and Conn's adenoma. 4. Patients with low renin hypertension, idiopathic hyperplasia and Conn's adenoma have overlapping values for plasma concentrations of potassium, renin and aldosterone and the aldosterone to renin ratio. Because primary aldosteronism subtypes are quantitative diseases, the true prevalence of primary aldosteronism cannot be defined. 5. The use of sensitive screening tests (e.g. aldosterone to renin ratio) gives a higher prevalence of diagnosed cases of primary aldosteronism, but not of surgically correctable forms. Therefore, there is no clinical evidence that primary aldosteronism is underdiagnosed. 6. There is a need for tests to predict the postoperative blood pressure outcome of surgery in subjects with Conn's adenoma.