A diagnostic composition for the detection and classification of PRRSV-infections in swine herds, including at least one antigen capable to bind a neutralizing antibody against the Type I-virus possibly present in the animal wherein the at least one antigen capable to bind a neutralizing antibody against the Type I-virus is a peptide of a PRRSV GP3 protein and is SEQ ID NO. 1 and at least one antigen capable to bind a neutralizing antibody against the Type II-virus possibly present in the animal and the necessary buffers and solutions typically present in an ELISA-assay.