The following is a summary of “Intra-individual Variability of Serum Aldosterone and Implications for Primary Aldosteronism Screening,” published in the May 2023 issue of Endocrinology & Metabolism by Maciel, et al.
The screening for primary aldosteronism (PA) typically involves measuring the aldosterone-to-renin ratio (ARR) with a minimum aldosterone level. The cutoff for minimum aldosterone levels varies from 10 to 15 ng/dL (277-415.5 pmol/L) using immunoassay. For a study, researchers sought to assess the intra-individual coefficient of variation (CV) of aldosterone and the aldosterone to direct renin concentration ratio (A/DRC) and its impact on PA screening.
The study included a large cohort of 216 patients with confirmed PA who underwent at least two screenings. A total of 671 aldosterone and DRC measurements were performed using the same chemiluminescence assays.
The median intra-individual CV for aldosterone and A/DRC was 26.8% and 26.7%, respectively. Approximately 40% of the patients had at least one aldosterone level below 15 ng/dL, 19.9% had at least two aldosterone levels below 15 ng/dL, and 16.2% had mean aldosterone levels below 15 ng/dL. A lower cutoff of 10 ng/dL resulted in false negative rates of 14.3% for a single aldosterone measurement, 4.6% for two aldosterone measurements, and only 2.3% for mean aldosterone levels. The positive rate for aldosterone thresholds considering the minimum level, was 85.7% for 10 ng/dL and 61.6% for 15 ng/dL. An A/DRC ratio greater than 2 ng/dL/µIU/mL had a true positive rate for PA diagnosis of 94.4% and 98.4% based on one or two assessments, respectively. The CV of aldosterone and A/DRC were not influenced by sex, the use of interfering antihypertensive medications, PA lateralization, hypokalemia, age, or the number of hormone measurements.
In patients with PA, aldosterone concentrations exhibited a high CV, leading to an increased rate of false negatives in a single screening for PA. Therefore, PA screening should include at least two screenings with simultaneous measurements of aldosterone and renin levels.