Original Article

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

Abstract

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.

1. Gitau MS, Asiago OH, Rogers OO, Reddy KS, PradeepKumar B, Sudheer A, et al. A Comprehensive review on Scrub typhus: Epidemiology, Transmission, Diagnosis and Management. Uttar Pradesh J Zool 2024; 45: 93-105.
2. Xu G, Walker DH, Jupiter D, Melby PC, Arcari CM. A review of the global epidemiology of Scrub typhus. PLoS Negl Trop Dis 2017; 11(11): e0006062.
3. Ramlingam G, Muthukumar A, Aridass D, Ganesan ST. Seroprevalence and clinical Profile of Leptospirosis and Scrub typhus in clinically Suspected Patients at a Tertiary care center: A Retrospective study from Theni, Tamil Nadu. Biomed Biotechnol Res J 2024; 8: 382-386.
4. Gautam R, Parajuli K, Tshokey T, Stenos J, Sherchand JB. Diagnostic evaluation of IgM ELISA and IgM Immunofluorescence assay for the diagnosis of Acute Scrub typhus in central Nepal. BMC Infect Dis 2020; 20: 138.
5. Kannan K, John R, Kundu D, Dayanand D, Abhilash KP, Mathuram AJ, et al. Performance of molecular and serologic tests for the diagnosis of Scrub typhus. PLoS Negl Trop Dis 2020; 14(11): e0008747.
6. Rawat V, Singh RK, Kumar A, Saxena SR, Varshney U, Kumar M. Epidemiological, clinical and laboratory profile of Scrub typhus cases detected by serology and RT-PCR in Kumaon, Uttarakhand: a hospital-based study. Trop Doct 2018; 48: 103-106.
7. Peniche-Lara G, Moo-Salazar I, Dzul-Rosado K. A Multiplex PCR assay for a differential diagnostic of rickettsiosis, Lyme disease and Scrub typhus. J Vector Borne Dis 2022; 59: 178-181.
8. Blacksell SD, Tanganuchitcharnchai A, Nawtaisong P, Kantipong P, Laongnualpanich A, Day NP, et al. Diagnostic accuracy of the InBios Scrub typhus detect enzyme-linked immunoassay for the detection of IgM antibodies in northern Thailand. Clin Vaccine Immunol 2015; 23: 148-154.
9. Jang WJ, Huh MS, Park KH, Choi MS, Kim IS. Evaluation of an immunoglobulin M capture enzyme-linked immunosorbent assay for diagnosis of Orientia tsutsugamushi infection. Clin Diagn Lab Immunol 2003; 10: 394-398.
10. Prakash JA, Kavitha ML, Mathai E. Nested polymerase chain reaction on blood clots for gene encoding 56 kDa antigen and serology for the diagnosis of Scrub typhus. Indian J Med Microbiol 2011; 29: 47-50.
11. Prakash JA, Abraham OC, Mathai E. Evaluation of tests for serological diagnosis of Scrub typhus. Trop Doct 2006; 36: 212-213.
12. Anitharaj V, Stephen S, Pradeep J, Park S, Kim SH, Kim YJ, et al. Serological diagnosis of acute Scrub typhus in Southern India: Evaluation of InBios Scrub typhus Detect IgM Rapid Test and comparison with other serological tests. J Clin Diagn Res 2016; 10: DC07-DC10.
13. Singhsilarak T, Leowattana W, Looareesuwan S, Wongchotigul V, Jiang J, Richards AL, et al. Short report: Detection of Orientia tsutsugamushi in clinical samples by quantitative real-time polymerase chain reaction. Am J Trop Med Hyg 2005; 72: 640-641.
14. Bakshi D, Singhal P, Mahajan SK, Subramaniam P, Tuteja U, Batra HV. Development of a real-time PCR assay for the diagnosis of Scrub typhus cases in India and evidence of the prevalence of new genotype of O. tsutsugamushi. Acta Trop 2007; 104: 63-71.
15. Saisongkorh W, Chenchittikul M, Silpapojakul K. Evaluation of nested PCR for the diagnosis of Scrub typhus among patients with acute pyrexia of unknown origin. Trans R Soc Trop Med Hyg 2004; 98: 360-366.
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IssueVol 17 No 4 (2025) QRcode
SectionOriginal Article(s)
DOI https://doi.org/10.18502/ijm.v17i4.19249
Keywords
Scrub typhus Orientia tsutsugamushi Real time-polymerase chain reaction Enzyme-linked immunosorbent assay Diagnostic tests
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How to Cite
1.
Ramalingam G, Muthukumar A, Aridass D, Subramani K, Ganesan ST. 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. Iran J Microbiol. 2025;17(4):600-605.