Swine influenza A serology: ELISA versus HI test

Abstract

Considering the subtype-specific assays separately, the best ELISA performances resulted in comparison with H1N1pdm HI test with 87.89% (95%CI:83.25-91.62) sensitivity, 46.65% (95%CI:43.09-50.23) specificity, 35.21% (95%CI:31.51-39.05) PPV and 92.11% (95%CI:88.99-94.58) NPV. The best concordance was shown with H3N2 HI assay (K=0.4601, 95%CI:0.4059-0.5144).Conclusion: One hypothesis for the higher ELISA positivity rate may be indicative of a seroconversion against another IAV strain, but the different target antibodies of the two tests might be also taken into account. The false negative sera may be due to an early immune response in some animals, not detectable by the commercial kit. Infact, as suggested by some authors, ELISA test may not identify positive animals at the early stage of infection effectively as the HI, particularly when the virus is introduced to a naive swine population. In conclusion, the ELISA performances need to be improved, but the commercial kit can be used in SIV infection serodiagnosis. However, caution may be used since the test could miss recently exposed animals.

Detection methods for influenza A H1N1 virus with special reference to biosensors: a review

“…ELISA sensitivity decreases after 10 5 (log 10/ml) viral load but QuickVue Influenza A+B test sensitivity decreases after 10 7 (log 10/ml) viral load [51]. In a different study, 1086 sera were analysed from 43 swine herds for different reference strains (H1N1, H3N2, H1N2, H1N1pdm) using ELISA with HI test and it was found that ELISA sensitivity and specificity were higher than HI that were 72.65% and 63.01%, respectively, for the detection of these strains [52,53]. According to these studies, ELISA cannot detect infection at an early stage.…”