Key result
In-house groEL PCR slightly outperforms IgM ELISA for diagnosing scrub typhus, yielding ~67% sensitivity.
Why the study?
Scrub typhus presents nonspecific clinical features during acute undifferentiated febrile illness that render early diagnosis difficult.
Does in-house groEL PCR improve the diagnosis of scrub typhus compared to IgM ELISA in patients with acute undifferentiated febrile illness?
Observational (n=221)
Does in-house groEL PCR improve the diagnosis of scrub typhus compared to IgM ELISA in patients with acute undifferentiated febrile illness?
Absolute Event Rate: 66.6% vs 62.8%
In-house groEL PCR provides comparable diagnostic accuracy to IgM ELISA for scrub typhus and can be a useful adjunct, especially in seronegative cases.
PURPOSE: Scrub typhus, caused by Orientia tsutsugamushi (O. tsutsugamushi) present nonspecific clinical features during manifestation of acute undifferentiated febrile illness (AUFI) to render its early diagnosis difficult. Accordingly, this study was undertaken to assess an in-house groEL PCR versus IgM ELISA for the diagnosis of scrub typhus and to genotypically characterise the randomly selected scrub typhus positive cases. METHODS: Blood samples, collected from two hundred twenty one (221) AUFI cases were subjected to groEL PCR and IgM ELISA for diagnosis of scrub typhus. Eleven randomly selected PCR positive cases were processed for DNA sequencing to determine the genetic diversity of O. tsutsugamushi in Chhattisgarh. RESULTS: Scrub typhus prevalence of 35.2% were detected among AUFI cases using both in-house groEL PCR and IgM ELISA. PCR alone showed sensitivity, specificity, positive and negative predictive values of 66.6% (CI: 55.08-76.94), 100% (CI: 90 to 100),100% (CI: 93.15 to 100) and 57.37% (CI: 44.05 to 69.96) while for IgM ELISA, these parameters were 62.8% (CI: 51.13-73.50), 100% (CI: 90 to 100), 100% (CI: 92.75 to 100) and 54.68% (CI: 41.75 to 67.18) respectively. PCR and ELISA could detect scrub typhus in 37.2% and 33.3% cases, when tested alone. groEL PCR detected the O. tsutsugamushi throughout the course of infection. Phylogenetic analysis depicted 5 of 11 positive cases belonged to Kuroki, Japan strain of O. tsutsugamushi, followed by Gilliam and Karp strain in 4 and 2 cases respectively. CONCLUSION: Scrub typhus should be considered in differential diagnosis of AUFI. groEL PCR may aid on to IgM ELISA test for optimum laboratory diagnosis of scrub typhus by its implementation especially in seronegative cases. Predominance of Kuroki-like strain followed by Gillian and Karp strains of O. tsutsugamushi in Chhattisgarh confirm variable geographical distribution of O. tsutsugamushi and provide the baseline epidemiological data which will eventually be used to help the researchers for developing better diagnostic tests and vaccine covering the predominant genotypes.
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Prakash et al. (2022) conducted an observational in Acute undifferentiated febrile illness (AUFI) / Scrub typhus (n=221). in-house groEL PCR vs. IgM ELISA was evaluated on Sensitivity for diagnosing scrub typhus. An in-house groEL PCR demonstrated a sensitivity of 66.6% and specificity of 100% for diagnosing scrub typhus, compared to 62.8% and 100% for IgM ELISA.
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