Assessment of two immunoassays for detection of IgM antibodies to scrub typhus using a serum panel

IntroductionScrub typhus is a vector borne zoonotic disease caused by Orientia tsutsugamushi, endemic to tsutsugamushi triangle. As the characteristic eschar is not always present, laboratory testing especially serological assay are the main stay of diagnosis.\n\nMaterials and methodsA total of 346 well-characterized sera from normals and patients with scrub typhus, malaria, dengue, enteric fever and gram negative septicaemia were tested for IgM antibodies by ST IgM ELISA and ST Ig M ICT\n\nResultsThe sensitivity and specificity of Scrub typhus IgM ICT and ELISA were 98.7, 96.3 and 97.4, 99.3 respectively. The IgM ICT and ELISA had a excellent concordance (99%) and a very high negative predictive value.\n\nConclusionThe findings from this study suggest that IgM ICT and IgM ELISA can be used interchangeably for serodiagnosis of scrub typhus in resource poor settings.