Epidemiology

For many years, primary aldosteronism (PA) was considered a rare (<1%) cause of hypertension and not worth investigating as a potential cause unless hypokalemia was present.[28] However, since 1992, evidence has accumulated that PA is much more common than was previously thought, and that most patients are normokalemic.[28][29][30]​​[31]​ Prevalence estimates vary considerably due to heterogeneity in source and type of data and non-standardized confirmation tests.[32] In one UK study of patients with newly diagnosed hypertension in the primary care setting, the prevalence of confirmed PA was 2.6%.[33] One study of people with established hypertension in Italy had a prevalence of PA of 5.9%, with the prevalence varying with the severity of hypertension (3.9% in stage 1 hypertension; 11.8% in stage 3 hypertension).[34]

At one Australian center, adoption of a policy in 1991 to screen for PA by measuring the plasma aldosterone/renin ratio in all patients referred with hypertension, and not just those with hypokalemia, led to a 10-fold increase in detection rate.​[27] This was associated with a 4-fold increase in the rate of removal of aldosterone-producing adenomas.​[27] The series of patients with PA at this center is increasing at a rate of 50 to 90 patients per year. Only 22% of patients diagnosed since 1992 were hypokalemic. The center reported an incidence of PA of 8.5% among 199 consecutive hypertensive normokalemic referred patients, and of 12% among 52 antihypertensive drug trial volunteers, with PA confirmed in each case by fludrocortisone suppression testing.​[35][36]

Since these initially reported findings, numerous other groups (spanning 6 continents and including the Mayo Clinic) similarly reported PA to be a much more common cause of hypertension than was previously suspected, with prevalence rates ranging from 3% to 32%, depending on the selectivity of hypertensive patients studied and the diagnostic criteria employed.[29][30]​[31]​​[37][38][39][40]​​​​[41][42]​​ In all of these series, <50% of patients diagnosed with PA were hypokalemic.

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