Screening for primary aldosteronism in a primary care unit.

Objective: Primary aldosteronism (PA) is a common cause of secondary hypertension but the reported prevalence varies. Few studies have been carried out in primary care. We investigated the prevalence of PA by screening with the aldosterone to renin ratio (ARR).

Design And Methods: Patients with hypertension were recruited from a primary care unit and investigated in a university hospital setting. Of 235 patients asked to participate 77% accepted. Antihypertensive medication apart from amiloride and spironolactone was maintained. The cut-off level for a positive ARR was lower than in clinical practice (> 50 pmol/ng with aldosterone > 350 pmol/l) to adjust for any suppressive effects of medication. A positive ARR was followed by a confirmatory evaluation.

Results: The frequency of confirmed PA was 1.6% and including cases with a positive ARR who refused further investigation it would be 3.3% at most. In primary hypertension angiotensin receptor blockers, angiotensin-converting enzyme inhibitors and thiazide diuretics markedly suppressed the ARR by increasing renin levels.

Conclusion: The detection rate of PA in our study is in the lower part of the wide range shown in previous studies. Larger population studies are needed to establish the true prevalence in primary care. Future studies may clarify if the present cut-off levels allow detection of very mild PA.