Evaluation of the MAGLUMI non-competitive angiotensin I chemiluminescence immunoassay for measuring renin activity in human plasma

OBJECTIVES: Plasma renin activity (PRA) measures the rate of renin converting angiotensinogen to angiotensin I in circulation and reflects the function of renin-angiotensin-aldosterone system (RAAS). The study aimed to demonstrate the performance of the MAGLUMI Angiotensin I assay for the measurement of PRA. METHODS: The MAGLUMI Angiotensin I assay was evaluated for precision, linearity, limit of blank (LoB), limit of detection (LoD), limit of quantification (LoQ), interferences, cross-reactivity and reference intervals. It was compared to liquid chromatography tandem mass spectrometry (LC-MS/MS) using 54 samples, and impact of clinical factors was assessed in 181 samples. RESULTS: The assay demonstrated repeatability of 1.5 %, 1.85%, and 1.6 % across three different pool concentrations, with corresponding within-laboratory imprecision values of 2.0 %, 2.5%, and 1.9 %. The linear range was [0.10, 24.0] ng/mL. The LoB, the LoD, and the LoQ were 0.03 ng/mL, 0.07 ng/mL, and 0.10 ng/mL, respectively. The interferences and cross-reactivity met the criterion for acceptable cross-reactivity (CR) with <±10 %. Reference interval validation shows <10 % of a total of 40 healthy individuals' plasma samples falling outside the established interval for standing and lying position. The MAGLUMI assay showed excellent agreement with LC-MS/MS for both angiotensin I (slope=1.076, intercept=0.109 ng/mL/h, r=0.987, p<0.001) and plasma renin activity (slope=1.131, intercept=-0.386 ng/mL/h, r=0.973, p<0.001). CONCLUSIONS: The MAGLUMI Angiotensin I chemiluminescence immunoassay is a sensitive and reliable commercial kit for detecting plasma renin activity. The assay exhibited robust analytical performance and strong agreement with LC-MS/MS.