A comparative study on diagnostic accuracy of rapid card test, IgM ELISA and real time-PCR in detecting scrub typhus infection: a cross-sectional study from tertiary care hospital

Scrub typhus, caused by Orientia tsutsugamushi, is a significant zoonotic illness in the Asia-Pacific region. Timely diagnosis is crucial, but overlapping symptoms and limitations of traditional diagnostic methods pose challenges. This study evaluates the diagnostic accuracy and utility of IgM ELISA, RT-PCR, and Rapid Card test for Scrub typhus, focusing on sensitivity, specificity, and practical applicability in endemic regions. This cross-sectional study was conducted on 192 patients with suspected Scrub typhus at a tertiary care hospital from June to November 2024. Diagnostic tests included Rapid Card, IgM ELISA, and RT-PCR. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy were calculated, along with clinical and demographic data. IgM ELISA had the highest sensitivity (96.30%) and specificity (100%), followed by Rapid Card (sensitivity: 93.55%, specificity: 99.38%) and RT-PCR (sensitivity: 92.86%, specificity: 99.44%). Common symptoms included fever (99.4%) and headache (95.8%). Positive cases were mostly males (56.7%-64.3%) and individuals aged 21-40 years. IgM ELISA shows high sensitivity and specificity for Scrub typhus, while RT-PCR aids early detection. The Rapid Card offers a quick field alternative. Combining molecular and serological methods can enhance diagnostic accuracy.