The invention relates to an in vitro diagnosis of heart failure. More specifically, the invention relates to specific antibodies of a peptide domain which is situated on either side of hinge region R76S77 of proBNP(1-108). In particular, the invention relates to a method of obtaining the aforementioned antibodies and to the use thereof in detecting blood proBNP(1-108) with the exception of BNP(1-76) and BNP(77-108). The invention also relates to a method of detecting blood proBNP(1-108), reagents and a kit for same.