Tehran University of Medical Sciences Iranian Journal of Microbiology 2008-3289 17 4 2025 07 29 600 605 EN Gopinath Ramalingam Viral Research and Diagnostic Laboratory, Department of Microbiology, Government Theni Medical College, Theni, Tamil Nadu, India Arundadhi Muthukumar Viral Research and Diagnostic Laboratory, Department of Microbiology, Government Theni Medical College, Theni, Tamil Nadu, India Dhanasezhian Aridass Viral Research and Diagnostic Laboratory, Department of Microbiology, Government Theni Medical College, Theni, Tamil Nadu, India Krishnapriya Subramani Viral Research and Diagnostic Laboratory, Department of Microbiology, Government Theni Medical College, Theni, Tamil Nadu, India Sucila Thangam Ganesan Viral Research and Diagnostic Laboratory, Department of Microbiology, Government Theni Medical College, Theni, Tamil Nadu, India 2024 12 16 2025 05 09 Background and Objectives: 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. Materials and Methods: 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. Results: 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. Conclusion: 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. https://ijm.tums.ac.ir/index.php/ijm/article/view/5205 https://ijm.tums.ac.ir/index.php/ijm/article/download/5205/1803