Received: December 1, 2008.

Accepted: December 9, 2008.

Abstract published online: January 12, 2009.

Full paper published online: February 28, 2009.

A BAYESIAN APPROACH TO ESTIMATE THE ACCURACY OF "IN-HOUSE" ELISA ASSAY TO MEASURE RABIES ANTIBODIES FROM COMPULSORY VACCINATED DOGS AND CATTLE

Nogueira AHC (1), Silva C (2), Gomes DE (2), Rosa ACG (2), Luvizotto MCR (3), Cardoso TC (2)

(1) São Paulo Agency of Agribusiness Technology, APTA, Araçatuba, São Paulo State, Brazil; (2) Laboratory of Virology, Department of Animal Health and Production, School of Dentistry, São Paulo State University, UNESP, Araçatuba, São Paulo State, Brazil; (3) Laboratory of Veterinary Pathology, Department of Animal Health and Production, School of Dentistry, São Paulo State University, UNESP, Araçatuba, São Paulo State, Brazil.

ABSTRACT: Rabies is a vaccine-preventable disease that causes acute encephalitis in mammals, and it is still a significant public health problem in numerous countries. Infected dogs represent the main vectors involved in human rabies. Additionally, cattle rearing close to geographic areas where vampire bats are found presents an important connection with rural epidemiology. We applied two "in-house" enzyme-linked immunosorbent assay (ELISA) methodologies, considered alternatives to measure antibodies from vaccinated dogs and cattle, without employing the gold standard approach. The ELISA assays were performed on individual serum samples taken from domestic adult dogs and cows compulsory vaccinated against rabies (147 urban dogs and 64 cows; n = 211). The sandwich and liquid-phase competitive ELISA (scELISA and lpcELISA), considered "in-house" assays, were performed according to previous works. The only statistical methodology that allows this study is the Bayesian approach, developed to replace the conventional Hui-Walter paradigm. For conditional independent Bayesian model (one population, two tests and no gold standard) the prior information for sensitivity and specificity of each test, mode, prevalence and transformed (, ) were submitted to Bayesian inference. The "in-house" lpcELISA revealed 16 – out of 261 serum samples – negative results, whereas in scELISA all results were positive. The Bayesian approach showed that prior information was specified for all parameters; posterior medians were SescELISA 89%, SpscELISA 88%, SplpcELISA 95% SelpcELISA 98%, and prevalence (pi) of 99%, without the use of gold standard analysis to measure specific anti-rabies antibodies.

KEY WORDS: rabies antibody, Bayesian analysis, ELISA assay.

CONFLICTS OF INTEREST: There is no conflict.

FINANCIAL SOURCE: CNPq, FAPESP.

CORRESPONDENCE TO:

TEREZA CRISTINA CARDOSO, Departamento de Apoio, Produção e Saúde Animal, FOA, UNESP, Araçatuba, SP, 16.050-680, Brasil. Phone: +55 18 3636 3200 ext. 1568. Email: tcardoso@fmva.unesp.br.