Reducing false positives pays in ELISA mycoplasma testing

Poultry producers should consider specificity when selecting a Mycoplasma ELISA test to avoid costs associated with false positives, advise researchers at Zoetis Inc.

New studies, presented at the 2014 American Association of Avian Pathologists conference, compared the specificity, or the ability to detect true negative samples, of three tests approved for Mycoplasma gallisepticum (MG), M. synoviae (MS) and MG/MS combination testing.¹

In the first two studies, Kit A (ProFLOK^® MG/MS) was significantly more specific (p ≤0.05), meaning it yielded fewer false positives, than another commercial ELISA assay for MG/MS testing, Kit B. Positive tests were confirmed using hemagglutination inhibition (HI).

The third study compared the specificity of Kits A, B and a third commercial ELISA test, Kit C, to HI. For MG, there were no significant differences between Kits A, B and C. There were also no significant differences for MS between Kit A and Kit C, but both were significantly more specific (p ≤0.05) than Kit B.

For MG/MS combination screening, Kits A and B were significantly more specific (p ≤0.05) than Kit C (for detailed results, see Table 1).

These differences in specificity have meaningful economic consequences for producers, says Dan Domingo, DVM, global director of diagnostic medicine for poultry at Zoetis.

“For each positive sample, separate HI assays must be performed. At this particular lab, HI tests cost $1 or $2 each,” he says. “Multiply that cost by the number of false positives for each test per year and we’re looking at a substantial economic difference.”

Table 1. Specificity of three commercial Mycoplasma ELISA kits compared to HI. Different superscript letters indicate a significant difference (p≤0.05).

¹ Zedek, a et al. Comparison of Commercially Available Mycoplasma Kit (abstract). Proceedings of the annual conference of the American Association of Avian Pathologists, 2014; 21-22.