A screening procedure for primary aldosteronism based on the Diasorin Liaison^® automated chemiluminescent immunoassay for direct renin

Abstract

Background: Primary aldosteronism (PA), the most common secondary cause of hypertension, can be screened for using the aldosterone/renin ratio. This ratio is raised in PA and its accuracy depends on the ability to measure plasma renin at extremely low concentrations. Methods: We compared two different procedures for assessing plasma renin. The conventional method, which measures plasma renin activity (PRA), is technically demanding and laborious, and the Diasorin Liaison w method, which measures plasma renin concentration (PRC), is an automated immunoassay. Results from each method were used to calculate the aldosterone/renin ratio (ARR) and the performance of the Diasorin Liaison w method compared with that of the conventional assay using receiver operator characteristic curves. Results: The analytical and functional sensitivity of the PRC method were 2.1 and 5 mIU/mL, respectively. Intra-and interassay precision were ,7.2% and 10.4%, respectively. There was significant (9%) prorenin interference. Samples with PRA . 1.0 ng/mL/h showed significant correlation with PRC (r ¼ 0.93; P , 0.05; n ¼ 146); however, with PRA , 1.0 ng/mL/h, no significant correlation occurred (r ¼ 0.14; P , 0.05; n ¼ 79). An aldosterone ( pmol/L)/PRC(mIU/mL) ratio of .35, in patients with aldosterone .300 pmol/L, resulted in 100% sensitivity and 93% specificity, when compared with the commonly accepted aldosterone ( pmol/L)/PRA (ng/mL/h) ratio of .750, in identifying patients who may suffer from PA. Conclusion: This study indicates the feasibility of using the automated PRC assay as a replacement for the conventional manual PRA assay in calculating the ARR as a first-line screen for PA.

Computed Tomography and Adrenal Venous Sampling in the Diagnosis of Unilateral Primary Aldosteronism

“…Despite this, in the CT group, the median postsurgical ARR (measured with plasma renin activity because direct renin concentration measurements may perform less well compared with plasma renin activity for low renin values) 30,31 was highly elevated in patients with an absent clinical outcome (107.1, interquartile range, 64.5-213.5; Table S2) and significantly greater than in patients with either partial (P<0.001) or complete clinical success (P<0.001; Figure 2; Table S2). Patients with AVS management displayed no significant differences in the ARR stratified for clinical outcomes ( Figure 2; Table S4).…”

Primary Aldosteronism: Changing Definitions and New Concepts of Physiology and Pathophysiology Both Inside and Outside the Kidney

“…Subtracting the amount of preformed angiotensin I in a control aliquot incubated at 4°C is suggested, but this may reduce the reproducibility of the test (462). The plasma concentration of the active (cleaved) form of renin (DRC) can be measured by radioimmunoassay, but more commonly measured by automated immunometric assay (123,146,396). Since renin does not affect blood pressure directly, but only through angiotensin, PRA is a better reflection of angiotensin II concentrations.…”

Novel Approach to Establishing an Aldosterone: Renin Ratio Cutoff for Primary Aldosteronism

“…4 To date, conventional methods used to correlate the 2 have uniformly involved direct head-to-head comparisons, typically in a small numbers of individuals. [5][6][7][8][9][10][11] This approach has many limitations. First, although PRA and DRC are purported to be mathematically correlated, 5-11 their relationship is not entirely linear, especially when renin levels are extremely high or low.…”

“…Such studies are generally small thus limiting their general applicability. [5][6][7][8][9][10][11] Moreover, the Endocrine Society has advised that the correlation between PRA and DRC is poor at lower renin levels, the domain of greatest importance for PA screening. 1 Indeed, differences in analytical method can result in as much as a 2-fold variation in ARR cutoffs and classification error.…”