Dados do Trabalho

Título

Sensitivity of serum aldosterone and renin measured by immunoassay for primary aldosteronism screening

Introdução

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. Nowadays, most of centers measure direct renin concentration (DRC) using an automated chemiluminescence

assay, but diagnostic cutoffs for aldosterone to DRC ratio (A/DRC) have not been addressed in previous guidelines, which proposed only conversion factors to change DRC to PRA. Recently, a single Italian study investigated the A/DRC cutoff for PA diagnosis in hypertensive patients. An A/DRC cut-off of 2.06 was associated with a negative predictive value of 99% for PA diagnosis. Among the patients with PA, the minimum aldosterone concentration was 14.7 ng/dL.

Objetivo

To evaluate intraindividual variability of serum aldosterone and aldosterone to direct renin concentration ratio (A/DRC) and its impact on PA screening sensitivity.

Método

We retrospectively evaluated the variability of aldosterone measurements in a large cohort of 216 patients with confirmed PA at the Hospital das Clinicas, University of São Paulo.

Resultados

A total of 671 aldosterone and DRC measurements were uniformly performed by the same chemiluminescence assays in a large cohort of 216 patients with confirmed PA and at least two screenings (Figure 1). Aldosterone concentrations varied from 3.9 to 784 ng/dL with a median value of 25 ng/dL. A/DRC ranged from 0.98 to 196 with a median value of 6.1 (Figure 2).The median intraindividual coefficient of variability for aldosterone was 26.8% (0 to 110%). Almost 40% of the patients had at least one aldosterone level < 15 ng/dL, 19.9% had at least two aldosterone levels < 15 ng/dL and 16.2% had mean aldosterone levels <15 ng/dL. A lower cut-off of 10 ng/dL was associated with false negative rates for PA screening of 14.3% for a single aldosterone measurement, 4.6% for two aldosterone measurements and only 2.3% for mean aldosterone levels. Considering the minimum aldosterone, sensitivity of aldosterone thresholds was 85.7% for 10 ng/dL, 78.2% for 12 ng/dL, 61.6% for 15 ng/dL and 44.4% for 20 ng/dL (Figure 3). An A/DRC > 2 had a sensitivity for PA diagnosis of 94.4% and 98.4% when based on one or two assessments, respectively (Figure 4).

Conclusão

Aldosterone concentrations had a high intraindividual variability in PA patients, which results in an elevated rate of false negative testing in a single screening for PA. If based on two screenings, an aldosterone threshold >10 ng/dL and an A/DRC > 2 had a very high sensitivity for PA diagnosis.