Cross-Reactivity of BNP, NT-proBNP, and proBNP in Commercial BNP and NT-proBNP Assays: Preliminary Observations from the IFCC Committee for Standardization of Markers of Cardiac Damage

B-type natriuretic peptide (BNP) is a 32 amino acid cardiac-synthesized hormone that reduces blood pressure and increases sodium excretion (1). Following proteolytic cleavage of proBNP, a 108-amino acid precursor, an N-terminal fragment (NT-proBNP) and BNP are released (2). Increased concentrations of BNP and NT-proBNP can be used clinically to monitor heart failure, but a lack of alignment between commercial BNP and NT-proBNP assays (3) can lead to confusion when clinicians or laboratorians compare results measured for the same analyte on different instruments. Some of this confusion arises from variable assay specificity regarding what peptides are being measured. We studied whether ( a ) BNP assays demonstrated cross-reactivity with NT-proBNP or proBNP, and ( b ) whether NT-proBNP assays demonstrated cross-reactivity with BNP or proBNP, by using 5 commercial BNP and 3 commercial NT-proBNP assays with 2 BNP, 2 NT-proBNP, and 2 proBNP materials.The NPs studied were: Peptide Institute synthetic BNP (aa 77–108), Scios human recombinant BNP (aa 77–108), HyTest human recombinant NT-proBNP (aa 1–76), Roche modified (amidated for stabilization) synthetic NT-proBNP, HyTest human recombinant proBNP (aa 1–108), and Scios glycosylated human recombinant proBNP. BNP assays evaluated were Abbott Architect, Abbott AxSYM, Bayer …