Comparative evaluation of four competitive/blocking ELISAs for the detection of influenza A antibodies in horses.

The research article studies the efficiency of four readily available enzyme-based tests (ELISAs) in detecting influenza A antibodies in horses, with the aim of selecting the most accurate test for equine influenza (EI) in case of an outbreak in New Zealand. The tests yield differing levels of specificity and sensitivity, making some of them more suitable than others for detecting EI.

Objective of the Study

• The primary purpose of this study was to find the most effective test for detecting equine influenza (EI) antibodies among four different enzyme-linked immunosorbent assays (ELISAs) available, as a measure to prepare New Zealand for a potential outbreak of this exotic animal disease.

Methodology

• The researchers used serum samples from non-infected, non-vaccinated horses in New Zealand (365 samples) as well as field-infected (99 samples) and experimentally infected horses in Australia (3 samples) to conduct the tests.
• Each of the four ELISA tests was evaluated based on their diagnostic specificities (DSP) and diagnostic sensitivities (DSE), essentially measuring how effectively they could detect EI presence or absence.

Results

• The results showed varying levels of DSP and DSE for each ELISA. ELISA-1 yielded 98.1% DSP and 99.0% DSE, ELISA-2 had 90.1% DSP and 99.0% DSE, ELISA-3 showed 98.1% DSP and 96.0% DSE, and ELISA-4 had 95.3% DSP and 99.0% DSE.
• The DSP and DSE results for ELISA-1 matched previously published data from Australian horses, confirming the test’s consistency.
• Additionally, Receiver Operating Characteristics (ROC) and frequency histogram analyses were performed, which essentially measure the performance of the diagnostic tests. The area under the curve (AUC) ranged between 0.996 to 0.979, with ELISA-1 possessing the highest AUC, indicating its superior reliability and accuracy.
• However, when looking at the clear distinction between negative and positive serum panels, ELISA-4 performed best, followed by ELISA-2, ELISA-1, and ELISA-3.
• In the experimentally infected horses, sero-positivity (the presence of specific antibodies in the horse’s blood serum) was detected between 7 and 9 days post-infection. ELISA-4 was the most sensitive in detecting this, followed by ELISA-1, ELISA-2, and ELISA-3.

Conclusion

• Overall, all four ELISAs performed relatively well in detecting EI from horse serum samples, but there were notable differences that could impact their usage in a real-world outbreak scenario.