The Diagnosis of Essential and Secondary Hypertension in Adults

The coexistence of hypertension and spontaneous or diuretic-induced hypokalemia is strongly suggestive of primary aldosteronism. However, it is important to remember that many (if not most) patients with primary aldosteronism do not have hypokalemia. In the past, screening for primary aldosteronism was accomplished by measuring urinary aldosterone levels after oral or intravenous salt loading. The sensitivity of these tests is 90% to 95%, and they carry a risk of precipitous elevation of blood pressure due to volume expansion or hypokalemia. Measuring the plasma renin and aldosterone levels can be used to test for hyperaldosteronism. Various cut points and ratios have been suggested, but the plasma aldosterone-to-renin ratio (cutoff point >25) is currently the most useful screening test for hyperaldosteronism. For this test the patient is asked to rise at 6 am and remain ambulatory for 2 hours, at which time the plasma aldosterone and renin levels are drawn. Beta-blockers and dihydropyridine calcium channel blockers must be stopped for 2 weeks, and spironolactone and loop diuretics must be stopped for 6 weeks before the test. Primary aldosteronism can be confirmed by the fludrocortisone suppression test.

Acknowledgments

Special thanks to Kathleen Dosh, MS; Greg Tan, MD; and Mark Povich, DO, for help during the initial editing of this paper.