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Diagnostic evaluation of IgM ELISA and IgM Immunofluorescence assay for the diagnosis of Acute Scrub Typhus in central Nepal.
BMC Infect Dis. 2020 Feb 13; 20(1):138.BI

Abstract

BACKGROUND

Scrub typhus is an acute febrile illness caused by the obligate intracellular bacterium, Orientia tsutsugamushi. Immunochromatography (ICT) and IgM ELISA are two of the routinely employed antibody based assays for diagnosis of Scrub typhus fever in Nepal, although the recommended gold standard diagnostic test is IgM Immunofluorescence assay (IFA). This study evaluated InBios Scrub Typhus Detect™ Immunoglobulin M (IgM) ELISA and IgM Immunofluorescence assays in single serum sample at the time of admission.

METHOD

Study participants (1585 suspected cases), were enrolled based on acute febrile illness with suspected scrub typhus cases in central Nepal. Blood sample was collected from the suspected patients of scrub typhus, presenting with acute febrile illness. IgM antibody to Orientia tsusugamushi was detected by using Scrub Typhus Detect™ Kit and an in-house IgM IFA. The IFA assay was performed with the Gilliam, Karp, Kato strains and O. chuto antigens following the ARRL protocol.

RESULT

Statistical analysis of IgM ELISA results when compared to reference test, IgM IFA results demonstrated the following characteristics, sensitivity 84.0% (95%CI: 79.73-87.68%), specificity 94.82% (95% CI: 93.43-95.99%), positive likelihood ratio 16.21% (95% CI: 12.71-20.67%), negative likelihood ratio 0.17% (95% CI: 0.13-0.21%), disease prevalence 22.08% (95% CI: 20.06 -24.21%), positive predictive value 82.12% (95% CI: 78.28-85.42%) and negative predictive value 95.44% (95% CI: 94.27-96.38%) respectively.

CONCLUSION

Although IgM IFA is considered the gold standard test for the diagnosis of scrub typhus cases, it is relatively expensive, requires trained personal and a microscope with fluorescence filters. Scrub typhus IgM ELISA may be the best alternative test and possible viable option for resource limited endemic countries like Nepal.

Authors+Show Affiliations

Department of Microbiology, Maharajgunj Medical Campus, Institute of Medicine, Kathmandu, Nepal. gautamrajen@gmail.com.Department of Microbiology, Maharajgunj Medical Campus, Institute of Medicine, Kathmandu, Nepal.Australian rickettsial reference laboratory, Geelong, Victoria, Australia.Australian rickettsial reference laboratory, Geelong, Victoria, Australia.Department of Microbiology, Maharajgunj Medical Campus, Institute of Medicine, Kathmandu, Nepal.

Pub Type(s)

Evaluation Study
Journal Article

Language

eng

PubMed ID

32054525

Citation

Gautam, Rajendra, et al. "Diagnostic Evaluation of IgM ELISA and IgM Immunofluorescence Assay for the Diagnosis of Acute Scrub Typhus in Central Nepal." BMC Infectious Diseases, vol. 20, no. 1, 2020, p. 138.
Gautam R, Parajuli K, Tshokey T, et al. Diagnostic evaluation of IgM ELISA and IgM Immunofluorescence assay for the diagnosis of Acute Scrub Typhus in central Nepal. BMC Infect Dis. 2020;20(1):138.
Gautam, R., Parajuli, K., Tshokey, T., Stenos, J., & Sherchand, J. B. (2020). Diagnostic evaluation of IgM ELISA and IgM Immunofluorescence assay for the diagnosis of Acute Scrub Typhus in central Nepal. BMC Infectious Diseases, 20(1), 138. https://doi.org/10.1186/s12879-020-4861-y
Gautam R, et al. Diagnostic Evaluation of IgM ELISA and IgM Immunofluorescence Assay for the Diagnosis of Acute Scrub Typhus in Central Nepal. BMC Infect Dis. 2020 Feb 13;20(1):138. PubMed PMID: 32054525.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Diagnostic evaluation of IgM ELISA and IgM Immunofluorescence assay for the diagnosis of Acute Scrub Typhus in central Nepal. AU - Gautam,Rajendra, AU - Parajuli,Keshab, AU - Tshokey,Tshokey, AU - Stenos,John, AU - Sherchand,Jeevan Bahadur, Y1 - 2020/02/13/ PY - 2019/05/22/received PY - 2020/02/06/accepted PY - 2020/2/15/entrez PY - 2020/2/15/pubmed PY - 2020/5/6/medline KW - ELISA KW - Nepal KW - Orientia tsutsugamushi KW - Scrub typhus SP - 138 EP - 138 JF - BMC infectious diseases JO - BMC Infect Dis VL - 20 IS - 1 N2 - BACKGROUND: Scrub typhus is an acute febrile illness caused by the obligate intracellular bacterium, Orientia tsutsugamushi. Immunochromatography (ICT) and IgM ELISA are two of the routinely employed antibody based assays for diagnosis of Scrub typhus fever in Nepal, although the recommended gold standard diagnostic test is IgM Immunofluorescence assay (IFA). This study evaluated InBios Scrub Typhus Detect™ Immunoglobulin M (IgM) ELISA and IgM Immunofluorescence assays in single serum sample at the time of admission. METHOD: Study participants (1585 suspected cases), were enrolled based on acute febrile illness with suspected scrub typhus cases in central Nepal. Blood sample was collected from the suspected patients of scrub typhus, presenting with acute febrile illness. IgM antibody to Orientia tsusugamushi was detected by using Scrub Typhus Detect™ Kit and an in-house IgM IFA. The IFA assay was performed with the Gilliam, Karp, Kato strains and O. chuto antigens following the ARRL protocol. RESULT: Statistical analysis of IgM ELISA results when compared to reference test, IgM IFA results demonstrated the following characteristics, sensitivity 84.0% (95%CI: 79.73-87.68%), specificity 94.82% (95% CI: 93.43-95.99%), positive likelihood ratio 16.21% (95% CI: 12.71-20.67%), negative likelihood ratio 0.17% (95% CI: 0.13-0.21%), disease prevalence 22.08% (95% CI: 20.06 -24.21%), positive predictive value 82.12% (95% CI: 78.28-85.42%) and negative predictive value 95.44% (95% CI: 94.27-96.38%) respectively. CONCLUSION: Although IgM IFA is considered the gold standard test for the diagnosis of scrub typhus cases, it is relatively expensive, requires trained personal and a microscope with fluorescence filters. Scrub typhus IgM ELISA may be the best alternative test and possible viable option for resource limited endemic countries like Nepal. SN - 1471-2334 UR - https://www.unboundmedicine.com/medline/citation/32054525/Diagnostic_evaluation_of_IgM_ELISA_and_IgM_Immunofluorescence_assay_for_the_diagnosis_of_Acute_Scrub_Typhus_in_central_Nepal_ L2 - https://bmcinfectdis.biomedcentral.com/articles/10.1186/s12879-020-4861-y DB - PRIME DP - Unbound Medicine ER -