Field evaluation of an equine influenza ELISA used in New South Wales during the 2007 Australian outbreak response

During the Australian epidemic of equine influenza in 2007, tens of thousands of horses were infected. From the resulting field data, 475 known infected and 1323 uninfected horses were identified to allow a post outbreak evaluation of the performance of the commonly used bELISA for influenza A under field conditions. A variety of techniques, such as ROC plots, area under the curve and hypothesis testing were used to assess the overall performance of the test. The test was deemed to be accurate (area under curve = 0.993 ± 0.003 standard error) and significantly informative (z = −32.0; p < 0.0001). Sensitivity and specificity of the test as used in the response (cut-point percentage inhibition ≥ 50) were 0.992 (95% CI: 0.979-0.997) and 0.967 (95% CI: 0.957-0.976), respectively.