Abstract Book of EAVLD2012 - eavld congress 2012

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RING TEST EVALUATION FOR THE DETECTION OF PRRSV ANTIBODIES IN ORAL FLUID
SPECIMENS USING A COMMERCIAL PRRSV SERUM ANTIBODY ELISA
Apisit Kittawornrat 1 , Chong Wang 1 , Gary Anderson 2 , Andrea Ballagi 3 , Andre Broes 4 , Susy Carman 5 , Kent
Doolittle 6 , Judith Galeota 7 , John Johnson 1 , Sergio Lizano 3 , Eric Nelson 8 , Devi Patnayak 9 , Roman Pogranichniy 10 ,
Anna Rice 3 , Gail Scherba 11 , Jeffrey Zimmerman 1
1 Iowa State University, 2 Kansas State University, 3 IDEXX Laboratories,Inc., 4 Biovet Inc., 5 University of Guelph, 6 Boehringer Ingelheim Vetmedica Inc.,
7 University of Nebraska, 8 South Dakota State University, 9 University of Minnesota, 10 Purdue University, 11 University of Illinois
Oral fluid, ELISA, Ring test, PRRSV
Introduction
A commercial PRRS serum antibody ELISA (IDEXX
Laboratories, Inc., Westbrook ME USA) was recently adapted to
detect anti-PRRSV antibody in oral fluid specimens (1). Based on
testing of field and experimental samples, diagnostic sensitivity
and specificity was estimated at 94.7% (95% CI: 92.4, 96.5) and
100% (95% CI: 99.0, 100.0), respectively, at a sample-to-positive
(S/P) cutoff of ≥ 0.40. 1 The purpose of this study was to evaluate
the reproducibility and repeatability of the PRRS oral fluid ELISA
in a ring test (check test) format.
Materials & methods
A total of 276 oral fluid samples were collected, completely
randomized, and sent for testing in 12 collaborating diagnostic
laboratories. In addition to the set of oral fluid samples, each
laboratory received the materials required for conducting the test:
ELISA plates (HerdChek® PRRS X3 ELISA, lot #40959-W721),
reagents, positive and negative controls, pre-diluted conjugate
antibody, and a copy of the standard operating procedure for the
PRRS oral fluid IgG ELISA. The laboratories tested the samples
and returned the results for analysis. Assay results were
analyzed as S/P ratios, with S/P ratios ≥ 0.40 considered
positive.
Results
Distribution of the results from the 12 laboratories is summarized
in Figure 1. As is shown in Figure 1, variation in S/P results
increased as the concentration of antibody in the sample
increased. Overall, this had little impact on categorical results.
That is, among the 276 samples tested by the 12 laboratories,
133 samples tested positive in all laboratories; 136 samples
tested negative in all laboratories, and 7 samples had discordant
results (Table 1). With the exception of sample #7, a discordant
result was reported in each case by only one of the 12
laboratories. Discordant results for sample #7 were reported at 3
laboratories, but this may be explained by the fact that all results
for sample #7 clustered close to the 0.40 cutoff.
Table 1: Summary of discordant results
Laboratory
Sample 1 2 3 4 5 6 7 8 9 10 11 12
1 0.03 0.00 0.02 0.05 0.00 0.08 0.03 0.51 0.01 0.00 0.06 0.02
2 0.05 0.01 0.00 0.01 0.01 0.04 0.04 0.03 0.00 0.72 0.00 0.01
3 0.03 0.01 0.04 0.05 0.00 0.04 0.02 0.01 3.03 0.02 0.02 0.00
4 1.19 0.03 0.04 0.06 0.00 0.04 0.01 0.08 0.03 0.02 0.04 0.04
5 0.07 0.04 0.01 0.00 0.02 0.02 0.04 0.00 0.07 0.96 0.00 0.02
6 0.05 0.03 0.00 0.02 0.02 0.00 0.02 0.03 0.02 0.01 0.04 1.21
7 0.27 0.26 0.26 0.39 0.45 0.27 0.33 0.41 0.40 0.26 0.26 0.25
Discussion & conclusions
The ring test results showed that the PRRS oral fluid IgG ELISA
was highly reproducible across laboratories. These results
support the routine use of this test in laboratories providing
diagnostic service to pig producers. Thus, herd monitoring based
on oral fluid sampling could be one part of a PRRSV control
and/or elimination program. Further, the successful adaptation of
one assay to the oral fluid matrix suggests that this approach
could provide the basis for monitoring specific health and welfare
indicators in commercial swine herds using a "pig friendly"
approach.
References
1. Kittawornrat, A et al.: 2012. Detection of PRRSV antibodies in oral fluid
specimens using a commercial PRRSV serum antibody ELISA. J Vet
Diagn Invest 24 (2):262-263
Figure 1: PRRS oral fluid antibody ELISA results from 237
samples tested in 12 laboratories