Performance Analysis and Evaluation of Quantitative Real Time PCR for Diagnosis of Scrub Typhus in North-East India

Abstract

Aims: Scrub typhus is a life-threatening infectious disease and always creating a diagnostic dilemma in terms of rapid turnaround time and accuracy, qRT PCR can become a very good option to achieve the desired result. This study was performed to evaluate the performance of qRT PCR in comparison to commonly used IgM ELISA and Weil-Felix tests to diagnose scrub typhus, in North-East India. Study Design: This was a hospital based prospective study. Place and Duration of Study: The study was conducted in the Department of Microbiology, of a tertiary care centre of North-East India over a period of 1 year (June 2019– May 2020). Methodology: Samples from suspected scrub typhus cases were screened by Weil-Felix test, followed by IgM ELISA for the confirmation of diagnosis. All the IgM positive samples and 20 highly suspected but ELISA negative samples were subjected to qRT PCR. Results: Out of 54 samples tested, 24 IgM ELISA positive samples and three IgM ELISA negative samples have shown the presence of bacterial DNA with quantification of DNA copies. It has also been observed that 21 out of 27 PCR positive samples (77.8%) were detected within the first seven days of illness. Conclusion: The performance of the commercial qRT PCR kit used in our study is satisfactory, which provides the extra advantage of quantification of DNA copies and increases diagnostic accuracy within the first week of fever.