Establishment of Reference Ranges for Aldosterone and Renin in a Multi-racial Community Using the Chemiluminescent Immunoassay (CLIA)

Despite old beliefs that Primary Aldosteronism (PA) is uncommon and warrants screening only when patients present with hypertension and hypokalemia, it is now believed that PA is in fact the most common cause of secondary hypertension, accounting for 5-13% of the hypertensive cohort, with an even higher prevalence among those with resistant hypertension. This stems from more efficient screening of this condition with the widespread use of the aldosterone to renin ratio. It is a disorder in which the adrenal cortex autonomously produces excessive aldosterone leading to sodium and water retention, resulting in a subsequent rise of blood pressure (BP), and down-regulation of renin through the renin-angiotensin-aldosterone system (RAAS) pathway.

Once considered a relatively benign condition, PA has been unequivocally shown to have effects beyond its effects on BP levels. Hypertension alone could not explain the higher adverse cardiovascular outcomes as PA patients were found to have higher cardiovascular mortality compared to patients with essential hypertension (EH) despite being matched for cardiovascular risks.

Elevated aldosterone levels were also shown to contribute to the excess morbidity and mortality. Recent studies have shown that PA is associated with a myriad of other co-morbidities, particularly cardiovascular and renal injuries, which might play a role in contributing to the elevated morbidity and mortality.

Traditionally, the activity of renin-angiotensin-aldosterone system is evaluated by measurement of plasma renin activity (PRA). However, PRA measurement is a complex procedure with poor inter-laboratory reproducibility, which makes it a limitation preventing more extensive use of PRA for diagnostic purposes. Direct renin assay is a new chemiluminescent renin assay, which utilizes the high specificity of monoclonal antibodies to detect the renin molecule, and is proven as a good alternative to the use of PRA. The use of this new assay appears to be simpler, faster and more reproducible than PRA, which is shown in a recent multi-center comparative study.

Literature shows aldosterone and renin levels differ between ethnicity and gender. There is no established reference intervals for these two hormone levels in Asian community.