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 the obligate intracellular bacterium known as Orientiatsutsugamushi. Although it presents with nonspecific clinical manifestation, early diagnosis and treatment oftenprevents it’s complication. Here in this study, we used two different diagnostic tools Scrub-polymerase chainreaction (PCR) and serologic Scrub IgM antibody based enzyme-linked immunosorbent assay (IgM ELISA) test.Out of 154 cases, total of 101 cases were found Scrub IgM-ELISA positive. Both serology and Scrub-PCR wasdone in total 96 cases. Out of 96 cases, 41.6% (n−40) were Scrub-PCR positive and 58.3% (n−56) cases werePCR negative. Eighty percent cases become serology positive (IgM ELISA) those who presented after 7 days butbefore 14 days of illness and least (54%) when presented before 1 week of illness. Twenty cases were found to beIgM positive but PCR negative. The mean duration of illness among those 20 patients who were IgM positive butPCR negative was found to 12.55 days. Only four cases were PCR positive but IgM negative. The mean durationof 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 entireduration of illness for early and accurate diagnosis so as to prevent the complications.