P-568: Apparent prevalence of primary aldosteronism in a referral practice: a retrospective study

Primary aldosteronism (PA), as first describe by Conn in 1955, has undergone conceptual revision in the last 20 years. First thought to exist as a rare entity, revisionists have presented newer criteria and detection methods increasing the original 0.5% incidence to as high as 32%. This retrospective study seeks to determine the apparent prevalence of PA in a referral clinic. The Aldosterone Renin Ratio (ARR) introduced in 1973 has become a principle element for clinical diagnosis, and consequently has engendered great discussion and some controversy. This study retrospectively evaluates 666 patients with resistant hypertension referred to our Center since 1995. The relative prevalence of PA in these patients was evaluated by the ARR calculated on the serum aldosterone (SA) and plasma renin activity (PRA). Of the total, 282 were males and 384 were females. For the entire group the mean values were: SA 10.84±7.15 ng/dl (Mean± SD), PRA 3.1±6.7 ng/ml/hr and ARR 29±48 units. Three subgroups were analyzed. Using an ARR value of ≥ 25, 200 patients were identified, 88 were male (28 African American (AA)) and 112 female (35 AA). Mean values were SA 12.2±8.5, PRA 0.21±0.2, ARR 79±63, and blood pressure (Bp) 171/98±26/16mmHg. Hypokalemia (< 3.5meq/L) was present in 38 (19%). Using an ARR value of ≥50, 118 patients were identified, 60 male (22 AA) and 58 female (21 AA). Mean Bp was 170/99±25/15, and 27(23%) were hypokalemic. Mean SA was 14.0±9.4, PRA 0.15±0.12, and ARR 112±64. However, the majority of these patients had SA values within the normal range. Out of the entire 666 patients the third subgroup found 25 patients with above normal SA ≥ 20 and a PRA≤1.0. Four (16%) had hypokalemia. Mean values for SA were 43±11.8, PRA 0.23±0.24, ARR 293±91, and Bp 173/104±28/15. Five of these patients underwent further evaluation. CT scan visualized an adrenal adenoma in four and normal adrenals in the fifth. In the later adrenal venous sampling was compatible with bilateral adrenal hyperplasia. The other four had surgical adrenalectomy with pathologically proven adenoma. None are now normotensive or without antihypertensive medication. When the criteria for PA are set with the ARR≥50, SA ≥20, and PRA≤1, the prevalence of presumed PA in this study group was 3.75% and confirmed PA was 0.75%. Am J Hypertens (2004) 17, 239A–240A; doi: 10.1016/j.amjhyper.2004.03.642