Determining significant cut off titre of single widal test for identifying presence of active typhoid/paratyphoid infection by studying baseline endemic widal titres from Meerut (UP), India & adjoining sub-urban regions

Abstract

Introduction: Globally enteric fever is one of the most infectious disease and endemic in all parts of India. Widal test is considered positive with a fourfold rise in titre in paired sera collected at intervals of one to two weeks or if the antibody titres are higher than the cut -off value in a single test. In endemic areas due to previous exposure and cross reacting antigens, the healthy population may contain antibodies capable of reacting at variable titres in widal test which is called as baseline antibody titre. Widal titres among healthy population of different areas differ substantially and depends upon the endemicity of typhoid in each area which has been changing over time. Aim: To establish the baseline endemic titre inorder to determine significant cutoff values for the single Widal test in Meerut and adjoining suburban areas. Material and Methods: 580 sera were tested by the Widal tube agglutination test from January 2012 to June 2013. Results: Baseline endemic titre for enteric fever in our region for TO and TH was found to be 1:80 and that for AH and BH was noted to be 1:40 and 1:20 respectively . Conclusion: For single Widal test, significant cutoff titre for TO and TH was ≥1:160 and that for AH and BH was ≥1:80 and ≥1:40 respectively. Single Widal test can be widely used as the diagnostic tool for enteric fever in endemic areas if we know the baseline endemic titres and this should be updated periodically with time.