The present disclosure relates to an antibody that specifically binds a mutated NT-proBNP having i) a mutation substituting arginine at position 46 with histidine or ii) a mutation substituting glutamic acid at position 43 with aspartic acid. Moreover, the present disclosure relates to a mutated NT-proBNP or fragment thereof. Further, envisaged by the present disclosure are kits containing the antibody of the present disclosure, or the mutated NT-proBNP of the present disclosure. The present disclosure also concerns a method for diagnosing heart failure.