Evaluation of diagnostic accuracy of the novel Scrub Typhus IgM ELISA Kit.

Background: Scrub typhus (ST) is a rickettsial infection endemic in Southeast Asia, with diagnostic challenges due to its clinical overlap with other febrile illnesses. Due to its accessibility and ease of use, Enzyme-linked Immunosorbent Assay (ELISA) is the widely preferred diagnostic tool.

Objectives: This study aims to evaluate the diagnostic performance of the Scrub typhus IgM Microlisa kit (J. Mitra & Co Pvt., Ltd.,) for detecting ST IgM antibodies, using the Scrub Typhus Detect™ IgM ELISA (Inbios International, Inc.) as a reference standard.

Methods: A retrospective observational study was conducted using 547 serum samples archived between January 2022 and December 2023. Samples were tested for ST IgM antibodies using the J. Mitra Scrub typhus IgM Microlisa kit (index test) and the Inbios Scrub Typhus Detect™ IgM ELISA kit (reference standard). Sensitivity, specificity, diagnostic accuracy, and likelihood ratios were calculated with 95 % confidence intervals.

Results: Of the 247 seropositive samples demonstrated a sensitivity of 87.45 % (95 % CI: 82.74-91.02), specificity of 97.67 % (95 % CI: 95.26-98.87), and diagnostic accuracy of 93.05 % (95 % CI: 90.61-94.9) by index kit. The performance of the index kit was consistent across different durations of fever, with the highest sensitivity observed in samples from patients with a fever lasting >7 days.

Conclusions: The J. Mitra Scrub typhus IgM Microlisa kit demonstrates high sensitivity, specificity, and diagnostic accuracy, comparable with that of the reference standard. It offers a reliable alternative for the routine laboratory diagnosis of scrub typhus, facilitating timely diagnosis and management.