Intra-individual Variability of Serum Aldosterone and Implications for Primary Aldosteronism Screening

Context Primary aldosteronism (PA) screening relies on an elevated aldosterone to renin ratio with a minimum aldosterone level, which varies from 10 to 15 ng/dL (277-415.5 pmol/L) using immunoassay. Objective To evaluate intra-individual coefficient of variation (CV) of aldosterone and aldosterone to direct renin concentration ratio (A/DRC) and its impact on PA screening. Methods A total of 671 aldosterone and DRC measurements were performed by the same chemiluminescence assays in a large cohort of 216 patients with confirmed PA and at least 2 screenings. Results The median intra-individual CV of aldosterone and A/DRC was 26.8% and 26.7%. Almost 40% of the patients had at least one aldosterone level <15 ng/dL, 19.9% had at least 2 aldosterone levels <15 ng/dL, and 16.2% had mean aldosterone levels <15 ng/dL. A lower cutoff of 10 ng/dL was associated with false negative rates for PA screening of 14.3% for a single aldosterone measurement, 4.6% for 2 aldosterone measurements, and only 2.3% for mean aldosterone levels. Considering the minimum aldosterone, true positive rate of aldosterone thresholds was 85.7% for 10 ng/dL and 61.6% for 15 ng/dL. An A/DRC >2 ng/dL/mu IU/mL had a true positive rate for PA diagnosis of 94.4% and 98.4% when based on 1 or 2 assessments, respectively. CV of aldosterone and A/DRC were not affected by sex, use of interfering antihypertensive medications, PA lateralization, hypokalemia, age, and number of hormone measurements. Conclusion Aldosterone concentrations had a high CV in PA patients, which results in an elevated rate of false negatives in a single screening for PA. Therefore, PA screening should be based on at least 2 screenings with concomitant aldosterone and renin measurements.

Automated summary

This study evaluated the coefficient of variation (CV) of aldosterone and aldosterone to direct renin concentration ratio (A/DRC) within individuals and its impact on primary aldosteronism (PA) screening. The results showed that the median intra-individual CV of aldosterone and A/DRC was 26.8% and 26.7%. A significant proportion of patients had aldosterone levels below the minimum threshold for PA screening. False negative rates were higher for single aldosterone measurements compared to multiple measurements. Therefore, PA screening should involve at least two screenings with concurrent aldosterone and renin measurements.