Significant discordance between point of care BNP values obtained by the i-STAT and the Beckman DXI 800, causing confusion in patient management when both methods are used interchangeably by clinicians

Abstract

B-type natriuretic peptide (BNP) is used as a biomarker of heart failure. In our hospital point of care (POCT) BNP test is performed in EDTA whole blood using i-STAT (Abbott Laboratories, Abbott Park, IL, USA) and in the clinical laboratory using EDTA plasma and the DXI 800 analyzer (Beckman, Brea, CA, USA). We compared BNP values in 88 patients obtained by using the i-STAT followed by using the DXI 800. The time difference between the two analyses varied from 32 min to less than 12 h. In addition, 11 specimens were simultaneously analyzed for BNP using both the i-STAT and the DXI 800 analyzer. Plotting BNP concentrations obtained by the DXI 800 in the x-axis (reference method) and the i-STAT values in the y-axis, we observed the following regression equation; y = 1.4758 x + 23.452 (n = 88, r = 0.96), indicating significant positive bias with the i-STAT. In addition, we also observed significant differences between BNP values obtained by the i-STAT and the DXI 800 in 11 specimens analyzed simultaneously. Therefore, clinicians should not use BNP concentrations obtained by the i-STAT interchangeably with BNP concentrations obtained by the DXI 800 analyzer for patient management.