Detection of antibodies to Newcastle disease virus in ostriches (Struthio camelus) by an indirect ELISA.

A two-graph receiver operating characteristic analysis, performed on the hemagglutination-inhibition (HI) and enzyme-linked immunosorbent assay (ELISA) test results of a Newcastle disease virus (NDV)-positive and NDV-negative control group of ostrich sera, proved that the ELISA was superior to the HI in both sensitivity and specificity. Comparison of results of the two assays performed on a panel of simulated positive sera ranging from very weak to very strong showed that the ELISA was at least 10 times more sensitive than the HI in detecting low levels of ostrich antibodies to NDV. The ELISA also has the advantage of using untreated serum in a single dilution as opposed to the HI test, which uses pretreated serum in titration.