Evaluation of Diagnostic Sensitivity of Rapid Immuno-Chromatographic Card Test (ICT) Against IgM ELISA for Serological Diagnosis of Scrub Typhus: An Experience at a Tertiary Care Centre in South-Eastern Rajasthan

Abstract

Introduction: Scrub typhus (ST) is a common but under-reported rickettsial disease in rural/sub-urban population of our country often resulting in severe complications and high mortality. Evaluation of ‘point of care’ tests like Rapid Immuno-Chromatographic Card Test (ICT) for diagnosis of ST is important to ascertain its utility in diagnosis of the disease in remote and peripheral settings. Aims: The present study was designed to evaluate the diagnostic sensitivity of Rapid ICT Test against IgM Enzyme-Linked Immunosorbent Assay (ELISA) for diagnosis of ST and to determine the prevalence, risk factors for ST infection in our setting. Materials and Methods: Setting and Design: Hospital based, cross-sectional & observational. The study included consecutive, ST suspects visiting a tertiary care hospital in south-eastern Rajasthan. Laboratory Investigations: Blood samples were collected and brief history was retrieved from the patient’s requisition forms. IgM ELISA and rapid ICT were performed as per manufacturer’s instructions. Statistical Analysis Used: The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) of rapid ICT against IgM ELISA was evaluated. The correlation between seropositivity and possible clinical/epidemiological risk factors for the disease were also analyzed using Chi-Square test. Results: One hundred eight (108) suspects were tested positive for ST by any one of the methods. The positivity was 45.83% (99/216) and 43.51% (94/216) by rapid ICT and IgM ELISA, respectively. Residence in rural settings, presence of fever with rash and/or eschar was suggestive of the ST disease, which often required hospitalization. Rapid ICT showed a good sensitivity and specificity against IgM ELISA. Conclusion: ST is an under reported disease in our setting and its role in acute febrile illness needs to be further assessed. Though ELISA is a more sensitive method for diagnosis of ST; Rapid ICT also shows good sensitivity and specificity for diagnosing ST and can be used in rural and peripheral settings. Rapid ICT test can be used for preliminary diagnosis of ST in peripheral and resource limited setting.

Keywords: Scrub typhus (ST), Orientia tsutsugamushi, Enzyme-Linked Immunosorbent Assay (ELISA), lateral flow rapid immuno-chromatographic card test (Rapid ICT)

Cite this Article

Deepti Dashora, Yogendra Kumar Tiwari, Priyanka Saini, Surabhi Sharma. Evaluation of Diagnostic Sensitivity of Rapid Immuno-Chromatographic Card Test (ICT) against IgM ELISA for serological diagnosis of Scrub Typhus: An Experience at a Tertiary Care Centre in South-eastern Rajasthan. Research & Reviews: A Journal of Microbiology and Virology. 2019; 9(1): 85–91p.