Figure 4From: Distinction of subtype-specific antibodies against European porcine influenza viruses by indirect ELISA based on recombinant hemagglutinin protein fragment-1Venn diagram of detection of NP-specific antibodies by commercial blocking ELISA (hatched ellipsis) and indirect ELISA (recombinant NP; red ellipsis) in porcine field sera (n = 207) compared with hemagglutination inhibition assays (white ellipsis). Eleven sera produced congruently negative results in all three tests.Back to article page