B-015 Analytical Verification of MR-proADM Biomarker in Human EDTA Plasma on Immunoassay Analyzer LIAISON® XL of Diasorin

Background Adrenomedullin (ADM) is a potent vasodilator peptide of 52-aminoacid belonging to the calcitonin family of peptides. Midregional pro-ADM (MR-ProADM) is a precursor for ADM that circulates is in a 1:1 ratio with it, and proportionally represents its levels and activity. Increased ADM circulating concentrations have been described for several disease states, including dysfunction of the cardiovascular system and sepsis. However, reliable ADM quantification has been hampered by the short half-life, the existence of a binding protein, and its physical properties. Hence, quantificacion of MR-proADM represents a more suitable option. The biomarker MR-proADM has been shown to be an accurate prognostic marker for outcome prediction in patients with lower respiratory infections, sepsis, urinary tract infections, and kidney disease. The objective of this study was the verification of the metrological characteristics and the verification of the linearity of quantitative measurement range, as declared by the manufacturer, of the LIAISON® Brahms MR-proADMTM on Liaison® XL (DiaSorin). Methods The verification was performed with two levels of quality controls (QC) from the manufacturer (x̄L=1,19 nmol/L and x̄H=5,48 nmol/L), and residual EDTA plasma samples from patients with an active sepsis code. The evaluation included the assessment of: • Detection capability (including limit of quantification (LoQ) and limit of detection (LoD), measuring three samples at the manufacturer's stated concentration (0.21 nmol/L and 0.09 nmol/L, respectively) in duplicate within 4 runs). • Precision (CV, %) and accuracy (bias, %) within, measuring 10 replicates of each QC level; and between run, measuring 5 replicates for each QC level within 5 runs. • Linearity of the quantitative range of measurement (six intermediate samples prepared by mixing a high concentration sample- XH=9.64 nmol/L- and a low concentration sample, XL=0.59 nmol/L; measured in triplicate). All studies were performed in accordance with the recommendations of the Clinical Laboratory Standards Institute guidelines. Statistical analysis was performed using Microsoft Excel®, 2016. Results All results with diluted samples presented a signal (RLU) higher than that detected in samples without analyte, so the LoD was verified. The precision at the LoQ concentration was 26.7% (acceptance criteria was set as <20%). CV for within-run precision were 4.3% and 2.0% and for between-run precision 6.8% and 7.9% for low (L1) and high (L2) control level, respectively. The average bias was 3.60% for L1 and 4.23% for L2, meeting acceptance criteria (<8%). Linearity was confirmed between 0.59 and 9.64 nmol/L (R2 = 0.995). The biases between the expected and the obtained value were ≤7% through the quantitative range of measurement, except for the lowest concentration sample (close to the quantitation limit). Conclusions Our study showed good compliance with the metrological characteristics declared by the manufacturer for LoD, precision, bias and linearity range. Although the LoQ was not verified, it is outside the clinical decision value in septic patients (< 2.25 nmol/L) and it is not deemed a limitation for clinical practice. Additionally, the Liaison XL® platform permits us to configure an emergency protocol circuit (24/7) with a TAT of 35 min.