Agar gel immunodiffusion test (AGID) evaluation for detection of bovine paratuberculosis in Rio de Janeiro, Brazil.
OBJECTIVE
The aim of this study is to evaluate the AGID serological test for detection of antibodies anti-Mycobacterium paratuberculosis and its possible adoption as diagnostic method in our field conditions.


METHODS
Bovine serum samples from dairy herds in Rio de Janeiro State, Brazil, were screened for the presence of antibodies against Myco. paratuberculosis using three different ELISA tests. A panel of 48 randomly selected sera were evaluated by an Agarose Gel Immunodiffusion (AGID) test using Protoplasmatic Paratuberculosis Antigen (PPA). AGID results were compared to the standards--the results of the three ELISA tests, and the specificity and sensitivity were calculated.


RESULTS
From 48 sera tested for AGID, 14 (29.17%) were positive and 34 (70.83%) were negative. AGID sensitivity was 57% with two false-positive reactions, and specificity was 92.5% with nine false-negative results. The positive predictive value was calculated in 85.7% for a confidence interval of 95%.


CONCLUSIONS
Due to its low sensitivity and specificity rates, AGID test has shown to be unsatisfactory as a screening diagnostic method for subclinical herd infection, but it can be useful as a confirmatory test for clinical suspect animals.
Department of Medical Microbiology, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil. ferreirarachel@hotmail.com
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Ferreira
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Fonseca
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Lilenbaum
D000362:Agar; D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood*; D001938:Brazil; D002417:Cattle; D002418:Cattle Diseases / Q000175:diagnosis*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods / Q000662:veterinary; D005779:Immunodiffusion / Q000379:methods / Q000662:veterinary; D016927:Mycobacterium avium subsp. paratuberculosis / Q000276:immunology*; D010283:Paratuberculosis / Q000175:diagnosis*; D012680:Sensitivity and Specificity
D000907:Antibodies, Bacterial; D000362:Agar