Evaluation Of IgM ELISA, Weil Felix Test And Indirect Immunofluorescence Assay In The Diagnosis Of Scrub Typhus.

Dr Pooja Raghunath; Dr P. Jose Paul; Dr Seema Oommen; Dr Sreeja Nair; Dr Archana Sasimohan

Volume : X, Issue : I, January - 2020

Evaluation Of IgM ELISA, Weil Felix Test And Indirect Immunofluorescence Assay In The Diagnosis Of Scrub Typhus.

Dr Pooja Raghunath, Dr P. Jose Paul, Dr Seema Oommen, Dr Sreeja Nair, Dr Archana Sasimohan

Abstract :

Scrub typhus is an acute feile illness caused by Orientia tsutsugamushi. There are reports of resurgence of scrub typhus in different parts of India including Kerala. Many cases go undiagnosed due to the lack of knowledge regarding the diagnostic test to be used. This study was undertaken at Pushpagiri Institute of Medical Sciences and Research Centre, Tiruvalla in the Department of Microbiology from January 2014 to September 2015, to assess the validity of various tests in diagnosing scrub typhus. A total of 94 samples were subjected to IgM ELISA, Weil Felix (WF) test and Indirect Immunofluorescence assay(IFA). The agreement between ELISA, IFA and Weil Felix test was assessed by κ (kappa) coefficient of Cohen using SPSS version 17. The sensitivity and specificity of ELISA with respect to IFA was 100% and 94.67% respectively, and that of IFA with respect to ELISA was 82.61% and 100% respectively. The sensitivity and specificity of WF test with respect to ELISA was 43.48 and 100% respectively and that of WF test with respect to IFA was 52.63% and 100% respectively. Although IgM ELISA is highly sensitive, it cannot be relied upon as the sole diagnostic test due to high false positivity. WF test is not a sensitive test, but when positive it is rather specific. IFA has high sensitivity and specificity, but is unsuitable for moderately equipped laboratories. Hence, we suggest that scrub typhus could be diagnosed using a combination of IgM ELISA and WF test and these tests should be included in the panel of serological tests ordered for patients presenting with undifferentiated feile illnesses.