NT-proBNP can be determined in a biological sample using at least one antibody which recognizes an epitope of NT-proBNP in both a glycosylated and non-glycosylated form of NT-proBNP. Said antibody is preferably an isolated polyclonal antibody or a mixture of monoclonal antibodies coated onto a particle, preferably coated onto said particle in a coating ratio of 6-60%, forming a layer or multiple layers of antibodies on said particle. The assay, realized in the form of a nephelometric or turbidimetric assay, can be applied to a wide range of automated clinical analyzers.