Endocrine Abstracts

Introduction: Measurement of aldosterone, the major mineralocorticoid secreted by adrenal cortex, is important for the screening of primary aldosteronism and for the clinical assessment of hypertensive patients. RIA remain widely used for the measurement of aldosterone but some automated immunoassays are emerging. The aim of our study was to evaluate the performances of a new automated aldosterone immunoassay.

Methods: Method imprecision of the Liaison® aldosterone assay (Diasorin), a fully automated immunoassay with chemiluminescence based detection, was determined with quality control materials and a pool of serum samples. Method comparison was performed with a commercial RIA (coat-a-count®, Siemens) in 91 patients samples.

Results: With quality control materials, between-run coefficients of variation (CV) were 8.3% at 4.9 ng/ml (n=15) and 5.3% at 25.4 ng/ml (n=11) with the Liaison® assay. For the serum pool with a concentration of 16.5 ng/ml, close to our laboratory cut-point of 14 ng/ml, the between-run coefficient of variation was 6.3% (n=8). A positive and significant correlation was observed between the two methods (r=0.96, P<0.001). For samples with aldosterone concentrations below 14 ng/ml (n=65), Passing and Bablock regression analysis provides a slope of 0.99 and an intercept of 0.02, without significant deviation of linearity. The mean difference observed on the Bland an Altman plot was 0.2 ng/ml. For samples with aldosterone concentrations higher than 14 ng/ml (n=23), Passing and Bablock regression analysis provides a slope of 1.00 and an intercept of −1.03, without significant deviation of linearity. The mean difference observed on Bland an Altman plot was 1.1 ng/ml.

Conclusions: Our study demonstrated satisfactory precision for the Liaison® aldosterone assay and results comparable to those of the RIA. Therefore, if our preliminary results are confirmed by larger studies, the Liaison® assay might be relevant for screening of primary aldosteronism and for the assessment of hypertensive patients.