Key result
Flock-level specificity of the ELISA for AMPV at processing was 97% using a cutoff of 1 positive sample and 100% for higher cutoffs, though antibiotic use increased false positives (P=0.02).
Why the study?
What is the flock-level diagnostic specificity of an ELISA for Avian metapneumovirus antibodies in turkeys?
Observational (n=37)
Yes
What is the flock-level diagnostic specificity of an ELISA for Avian metapneumovirus antibodies in turkeys?
The ELISA for AMPV has high flock-level specificity at processing, though cross-reactions may occur with antibiotic use or B. avium vaccination.
High specificity supports ELISA for AMPV flock screening at processing with adjusted cutoffs; leaves open antibiotic effects on false positives.
Routine serologic testing for Avian metapneumovirus (AMPV) infection of turkey flocks at slaughter is currently being used to monitor changes in the occurrence of AMPV infection in endemic areas and can also be used to detect the emergence of infection in currently unaffected areas. Because of the costs associated with false-positive results, particularly in areas that are free of AMPV infection, there is a need to obtain improved estimates of flock-level specificity (SP). The objective of this study was to estimate flock-level SP of a program to monitor AMPV infection in turkey flocks at processing using a standard enzyme-linked immunosorbent assay (ELISA). A study was carried out in which 37 AMPV-free flocks from 7 Midwest operations were followed serologically. Six percent, 3%, and 0.2% of total samples tested AMPV positive at 8 weeks, 12 weeks, and at processing, respectively. Overall, flock-level SP increased as the cutoff increased and as age increased. Flock-level SP at processing was 97%, if a cutoff of 1 was used (the flock was classified as positive if at least 1 sample tested positive), and 100%, if any other cutoff was used. Administration of antibiotics (P = 0.02) and vaccination for Bordetella avium (P = 0.08) were positively associated with the probability of (false) positive test results. These findings suggest possible cross-reactions with other infections and highlight the need to consider variable diagnostic performance depending on farm conditions.
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Muñoz‐Zanzi et al. (2009) conducted an observational in Avian metapneumovirus (AMPV) infection (n=37). Enzyme-linked immunosorbent assay (ELISA) for AMPV antibodies was evaluated on Flock-level specificity at processing. Flock-level specificity of the ELISA for AMPV at processing was 97% using a cutoff of 1 positive sample and 100% for higher cutoffs, though antibiotic use increased false positives (P=0.02).
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