Evaluation of serological tests in the diagnosis of scrub typhus

Scrub typhus is a leading cause of acute undifferentiated febrile illness in India. Overlapping clinical presentation and very low incidence of characteristic eschar makes serology the main stay of diagnosis. IgM ELISA is the most common test performed in tertiary care centres along with rapid diagnostic tests (RDT) and Weil Felix with varying sensitivity and specificityThe present study was conducted to compare the RDT’s and Weil Felix with IgM ELISA and analyse the demographic and clinical profile of scrub positive patientsSerum samples from clinically suspected scrub typhus patients admitted in a tertiary care hospital were tested by Weil Felix, RDT and IgM ELISA. Scrub typhus was confirmed in 38 of the 100 clinically suspected patients by IgM ELISA. Fever was the most common presenting symptom with significant proportion of patients being exposed to vegetation (p=0.0001).Sensitivity of Weil Felix and RDT was 42.1% and 84.2% respectively. Acute Kidney injury was the most common complication and mortality rate was 7.9%.Weil Felix is not a reliable test for scrub typhus diagnosis due to low sensitivity. Results of positive RDT’s can used for early initiation of specific treatment and IgM ELISA can be used as a confirmatory test in highly suspected cases.