Background and Objectives: Scrub typhus due to Orientia tsutsugamushi is a leading cause of acute undifferentiated febrile illness (AUFI) in India; however, the diagnosis poses a great challenge. The objectives of this study were to estimate the seroprevalence and performance of both a rapid immunochromatographic test (ICT) and real-time polymerase chain reaction (PCR) compared with standard immunoglobulin M (IgM) enzyme-linked immunosorbent assay (ELISA). Materials and Methods: We performed a prospective, hospital-based study in patients with AUFI. A total of 188 patient samples were tested after excluding the samples negative for other common fevers. Serodiagnosis was carried out using a rapid ICT and IgM-ELISA. For the comparison of sensitivity and specificity, the IgM ELISA was used as a reference standard, and its performance characteristics were compared to those of the ICT. All ELISA-positive samples were tested for molecular diagnosis by real-time PCR. Results: Eighty-two (43.6%) of the 188 patients were positive for scrub typhus by IgM ELISA. ICT was positive in 78 (41.5%) patients. Against IgM ELISA, the performance of the ICT reflected a sensitivity and specificity of 93.9/99.1% (positive predictive value/negative predictive value = 98.7/95.5%). Positive PCR results were obtained for 79 (96.3%) of the ELISA-positive samples with a positive consistency rate between tests. Conclusions: Our results support a substantial disease burden of scrub typhus in febrile patients in this area. The rapid ICT performed accurately in the tested conditions, which may be of great convenience for rapid screening in a number of health care settings.
Panda et al. (Wed,) studied this question.