Supplementation of the commercial IDEXX ELISA with blocking agents for the detection of antibodies to porcine reproductive and respiratory syndrome (PRRS) virus and the use of immunoglobulin G purified from serum samples had no effect on unexpected positive results. These findings strongly suggest that the unexpected positive signals were due to an antibody-antigen reaction. Simple competitive and blocking ELISAs were developed by modifying the IDEXX ELISA. All unexpected positive sera were negative in the indirect fluorescent antibody test, and 89.0% were negative in both the competitive and blocking ELISAs. These results show that both ELISAs are capable of distinguishing positive and unexpected positive sera and suggest that most of the unexpected positive signals obtained in the IDEXX ELISA are false positives.
(Research Team for Viral Diseases, TEL +81-29-838-7708)
Reference:
Okinaga, T. et al. (2009) Vet. Rec. 164:455-459.
