Valutazione delle caratteristiche analitiche di un nuovo metodo di dosaggio del BNP

Evaluation of the analytical characteristics of a new method for determination of BNP. Recent studies demonstrated that there are marked differences in analytical performances and results obtained with different methods for BNP assay. The aim of this study is to evaluate the analytic performance and results obtained with a novel BNP assay using the platform AIA 2000 Tosoh Bioscience. The novel method for BNP tested in the present study, named ST AIA-PACK BNP, is a two-site immunoenzymometric assay. The BNP assay uses a combination of two monoclonal antibodies and a fluorescent detection. The limits of blank (LoB) and detection (LoD) for BNP assay were determined according to the CLSI EP17-A protocol. As a result, the calculated LoB and LoD values were 2.6 ng/L and 5.4 ng/L, respectively. The assay reproducibility was evaluated in accordance with the CLSI EP5-A2 protocol by repeatedly measuring 3 different EDTA plasma samples for consecutive 20 working days, containing on average 8.70 ng/L, 21.72 ng/L, and 38.72 ng/L of BNP, respectively; CV values between 19.4% and 5.0% were obtained. The between-runs imprecision profile was performed by repeatedly measuring in 20 different runs 9 EDTA blood sample, with concentration from 5 ng/L to 778 ng/L, collected from healthy subjects and patients with cardiac disease. The calculated limits of quantitation (LoQ) at 20% CV and 10% CV were 9 and 30 ng/L of BNP, respectively. The results obtained with the new BNP Tosoh method was compared with those found with the TRIAGE Beckman-Coulter. A very close linear regression was found when the BNP values were measured with Tosoh and Beckman-Coulter methods in 133 EDTA plasma samples of healthy subjects and cardiac patients. However the Tosoh method showed on average a significant negative bias (i.e., underestimation) of BNP values compared to Beckman-Coulter of -40.0%±8.8% (mean±SD, p<0.0001). A significant correlation was also found between the BNP and NT-proBNP values, respectively measured with AIA Tosoh and ECLIA Roche methods, although weaker than that obtained comparing the two BNP assays. These data suggest that the ST AIA-PACK BNP assay has reproducibility and analytic sensitivity similar to the common automated methods commercially available at present time. In particular, the AIA method measures the recommended cut-off (i.e., 100 ng/L) by international guidelines with an imprecision less than 5%. These data also suggest that clinicians should be carefull when comparing results from different laboratories, which use different BNP assays.