Authors: Jeyakumari D, Jaberlin Sneha AJ, Gopal R
Background: Enteric fever is endemic in developing countries like India. Widal test in a single serum sample is often the only test relied upon for laboratory diagnosis. The test is considered positive if the antibody titres are higher than the cut – off value in a single test or a rising titre in paired sera. But normal baseline titres in healthy population and cutoff values have not been established in our area. So the aim of our study was to determine the base line titres of antibodies among apparently healthy populations and to define the significant titres of widal test. Materials and Methods: Samples were initially screened by Widal slide agglutination test and further confirmed by the Quantitative tube agglutination test. Results: Among the 500 samples from apparently healthy individuals, 260 samples were positive for agglutinins. 141 were positive for ‘O’ agglutinin and 163 were positive for ‘H’ agglutinin of Salmonella typhi. Among 141 samples, 30 showed agglutination up to 1in 20 titre, 100 up to 1in 40 and 25 (4.8%) up to 1in 80. Among 163 samples, 18 showed a titre of 1 in 20, 120 showed a titre of 1 in 40 and 21(4.2%) up to 1 in 80. Conclusion: When a single widal titre is used for the diagnosis of enteric fever in our locality, it will be more appropriate to change the currently used cutoff levels against S.typhi to ≥ 1 in 160 for anti-O and ‘H’ agglutinins remains the same of ≥ 1 in 160.
Keywords: Baseline titer, Widal test, Healthy population