Clinical and Diagnostic Laboratory Immunology, June 2005, p. 685-692, Vol. 12, No. 6
1071-412X/05/$08.00+0 doi:10.1128/CDLI.12.6.685-692.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.
Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, 2015 Linden Dr., Madison, Wisconsin 53706-1102,1 Department of Veterinary Population Medicine, College of Veterinary Medicine, University of Minnesota, 1354 Eckles Ave., St. Paul, Minnesota 55108,2 Minnesota Board of Animal Health, 90 W. Plato Blvd., St. Paul, Minnesota 55107,3 University of Minnesota Veterinary Diagnostic Laboratory, 1333 Gortner Ave., St. Paul, Minnesota 55108,4 School of Veterinary Medicine, University of Pennsylvania, New Bolton Center, 382 West Rd., Kennett Square, Pennsylvania 19348-16925
Received 18 February 2005/ Returned for modification 7 March 2005/ Accepted 14 March 2005
Five diagnostic tests based on enzyme-linked immunosorbent assay (ELISA) technology for bovine paratuberculosis were evaluated by using individual serum or milk samples from 359 dairy cattle in seven paratuberculosis-free herds and 2,094 dairy cattle in seven Mycobacterium paratuberculosis-infected dairy herds. Three independent laboratories using three different culture procedures completed fecal cultures for M. paratuberculosis on these cattle and found 417 cows to be shedding M. paratuberculosis in their feces. An animal that was fecal culture positive for M. paratuberculosis by any of the three laboratories was considered a confirmed case of infection. The specificity of three ELISAs (two on serum and one on milk) was
99.8%. The specificity of the remaining two ELISAs, both done on serum, was 94.9 and 84.7%. Four of the five ELISAs evaluated produced similar sensitivity in detecting fecal culture-positive cattle (27.8 to 28.9%). Serum ELISA "D" had the lowest specificity (84.7%) and the highest sensitivity (44.5%), but if the cutoff value defining a positive test was changed from 125 to 250% (of the positive control) the sensitivity and specificity, 31.8 and 97.5%, respectively, were comparable to those of the other four assays. If the case definition for M. paratuberculosis infection was based on the culture results of a single laboratory instead of the combined results of three laboratories, ELISA sensitivity estimates were 45.7 to 50.0%. With the exception of ELISA D, assay agreement was high (kappa 0.66 to 0.85) for categorical assay interpretations (positive or negative), but linear regression of quantitative results showed low correlation coefficients (r2 = 0.40 to 0.68) due to the fact that ELISA results for some cows were high in one assay but low in another assay. Likelihood ratio analysis showed a direct relationship between the magnitude of ELISA result and the odds of a cow shedding M. paratuberculosis in its feces. If used judiciously and interpreted quantitatively, these ELISAs are useful tools in support of paratuberculosis control programs in dairy herds.
This article has been cited by other articles:
Copyright © 2009 by the American Society for Microbiology. For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»