Endocrine Abstracts

Background: Identifying hypertensive patients with primary aldosteronism (PA) using the aldosterone to renin ratio (ARR) is crucial for optimizing their treatment. Various medications used to treat hypertension are known to alter levels of aldosterone and renin, thus affecting the ARR. As withdrawing all medication before screening is often unrealistic, we aimed to determine the degree of interference of some commonly used agents on the ARR using assays on the automated IDS-iSYS platform (Boldon, UK).

Methods: We investigated a cohort of 65 patients (32 males and 33 females) with essential hypertension (EH), renovascular hypertension, PA or Cushing’s syndrome. Fifty-seven of the patients were taking anti-hypertensive medication at the time of screening. Mean age was 59±17 years. For the majority of patients, both supine and standing samples were available. We used IDS-iSYS aldosterone and direct renin assays to measure the ARR for each sample. A previously determined ARR cut-off of >1.1 ng/dl per μU per ml was used to indicate the presence of PA.

Results: In patients with PA, 15 of 19 samples had an ARR value above the cut-off. All samples from patients with renovascular hypertension (n=16) and Cushing’s (n=3) displayed a negative ARR regardless of medication. In samples from patients with EH (n=78), 20 false positive ARRs were measured, 16 of which were standing samples. Seventeen of the 20 samples were from patients taking β-blockers, whereas two were from patients not taking any hypertension medication.

Conclusions: Interrupting hypertension medication for ARR screening gives the most accuracy but is not ideal for the patient. We observed a false positive outcome in 26% of samples from patients with EH, which was mostly associated with β-blockers and/or standing sampling position. Therefore, it may not be necessary to withdraw all drugs for the ARR screening as long as the effects are taken into account when interpreting results.