COMPARISON OF QUANTITATIVE TUBE AGGLUTINATION AND SEMIQUANTITATIVE SLIDE AGGLUTINATION TEST FOR DIAGNOSING OF THE SUSPECTED CASES OF ENTERIC FEVER

Abstract

Introduction: Enteric fever is the major health problem of developing country like India, with a notable morbidity and mortality. Isolation of Salmonella the causative agent from Blood is the standard laboratory method for diagnosis, but it is not available at PHC level. So, rapid and affordable diagnostic test like Widal tube and slide agglutination test are used. The present study was done to comparatively evaluate the Widal slide agglutination and tube agglutination test in detecting enteric fever.

Methods: A total of 500 patients with clinical presentation suggestive of enteric fever were included in the study whose venous blood was collected. All the samples were tested for the presence of anti O and anti H agglutinins against S. typhi and S. paratyphi A by semi quantitative slide and quantitative tube agglutination tests as per standard protocols. The titers of 1:80 (O agglutinins) and 1:160 (H agglutinins) were taken as the significant titer for the diagnosis of enteric fever.

Results: Out of 500 collected samples, 183 (36.6%) was positive by slide agglutination test, whereas, only 145 (29%) were positive by tube agglutination method. The slide test had a sensitivity of 97.2%, specificity of 88.1%, positive predictive value of 77% and negative predictive value of 98.7% as compared to Widal tube agglutination test.

Conclusions: Due to high false positivity shown by slide test, it is suggested that serological diagnosis should not be made solely on the basis of slide test rather its results should be confirmed by using Widal tube agglutination test.

Keywords: Enteric fever, Slide agglutination test, Widal tube agglutination test, Sensitivity, Specificity