Comparison of Weil Felix Test and IgM ELISA in the diagnosis of Scrub Typhus in Kangra, Himachal Pradesh. -

Introduction: Rickettsial diseases are an important cause of fever of unknown origin. They pose a serious threat to public health if not diagnosed properly. Diagnosis of these diseases is a challenge to both clinicians and laboratorians. Kangra region of Himachal Pradesh is endemic for Scrub Typhus. Various serological tests are available, of which the Weil Felix Test (WFT) is most widely used. Recently, IgM ELISA for Scrub Typhus has been introduced in our set up for the diagnosis of Scrub Typhus. Objective: To evaluate and compare results of Weil Felix Test and IgM ELISA in the diagnosis of Scrub Typhus. Materials and Methods: A prospective study was conducted amongst the patients suspected of suffering from Scrub Typhus w.e.f. March 2013 through February 2014. IgM ELISA Scrub Typhus was carried out on sera of suspected patients. Those positive for Scrub Typhus were also evaluated by the Weil Felix Test. The WFT was carried out on the microtitre plate agglutination test, using doubling dilutions from 1:40 to 1:320. Sera having titres more than 320 were further screened till end titre dilution. Results: 1653 patients suspected to be suffering from Scrub Typhus were enrolled for the study. The mean age of the patients was 30.93+-17.02 years. Majority (56.87%) of patients were females. 487 patients were serologically positive for Scrub Typhus by IgM ELISA. Out of these 487 patients, 353 were also positive by Weil Felix OXK agglutination test. The diagnostic titre of Weil Felix considered positive was titre 160. Sensitivity and Specificity of WFT in relation to IgM ELISA at a titre of 160 was 72.5% and 91.4% respectively. As the titres increased, the WFT was more specific. Conclusion: Though IgM ELISA for Scrub Typhus is more sensitive, rapid and specific for testing large number of sera in early phase of disease, the specificity of Weil Felix increases with increasing titre.