Comparison of diagnostic performance between serological tests (Scrub IgM-ELISA) and Scrub-PCR for scrub typhus fever in an Indian tertiary care teaching hospital

Abstract

Scrub typhus is a mite borne transmittable disease caused by obligate intracellular bacterium known as Orientia tsutsugamushi. Though, it presents with nonspecific clinical manifestation, early diagnosis and treatment often prevents it’s complication. Here in this study we used two different diagnostic tools Scrub PCR and serologic Scrub IgM ELISA test. Out of 154 cases, total 101 cases were found scrub IgM ELISA positive. Both serology and scrub PCR was done in total 96 cases. Out of 96cases 41.6% (n-40) were Scrub PCR positive, 58.3% (n-56) cases were PCR negative. 80% cases become serology positive(IgM ELISA) those who presented after 7days but before 14days of illness and least (54%) when presented before 1week of illness .20 cases were found to be IgM positive but PCR negative. The mean duration of illness among those 20 patients (IgM positive but PCR negative) were found to 12.55 days so that the antigen detection may be negative at that stage. Only 4 no of patients had PCR positive but IgM negative. The mean duration of illness was 6.2 days among those four patients so that the antibody conversion was not detectable at that phase. Therefore, the combination of molecular and serological tests needs to be used so that it can cover the entire duration of illness for early and accurate diagnosis so as to prevent the complications.