scholarly journals Diagnostic Accuracy of the InBios Scrub Typhus Detect™ ELISA for the Detection of IgM Antibodies in Chittagong, Bangladesh

2018 ◽  
Vol 3 (3) ◽  
pp. 95 ◽  
Author(s):  
Stuart Blacksell ◽  
Hugh Kingston ◽  
Ampai Tanganuchitcharnchai ◽  
Meghna Phanichkrivalkosil ◽  
Mosharraf Hossain ◽  
...  
Keyword(s):  
General Population ◽  
Diagnostic Accuracy ◽  
Diagnostic Tests ◽  
Scrub Typhus ◽  
Febrile Illness ◽  
High Sensitivity ◽  
Immunofluorescence Assay ◽  
Immunoglobulin M ◽  
Regional Assessment ◽  
Igm Elisa

Here we estimated the accuracy of the InBios Scrub Typhus Detect™ immunoglobulin M (IgM) ELISA to determine the optimal optical density (OD) cut-off values for the diagnosis of scrub typhus. Patients with undifferentiated febrile illness from Chittagong, Bangladesh, provided samples for reference testing using (i) qPCR using the Orientia spp. 47-kDa htra gene, (ii) IFA ≥1:3200 on admission, (iii) immunofluorescence assay (IFA) ≥1:3200 on admission or 4-fold rise to ≥3200, and (iv) combination of PCR and IFA positivity. For sero-epidemiological purposes (ELISA vs. IFA ≥1:3200 on admission or 4-fold rise to ≥3200), the OD cut-off for admission samples was ≥1.25, resulting in a sensitivity (Sn) of 91.5 (95% confidence interval (95% CI: 96.8–82.5) and a specificity (Sp) of 92.4 (95% CI: 95.0–89.0), while for convalescent samples the OD cut-off was ≥1.50 with Sn of 66.0 (95% CI: 78.5–51.7) and Sp of 96.0 (95% CI: 98.3–92.3). Comparisons against comparator reference tests (ELISA vs. all tests including PCR) indicated the most appropriate cut-off OD to be within the range of 0.75–1.25. For admission samples, the best Sn/Sp compromise was at 1.25 OD (Sn 91.5%, Sp 92.4%) and for convalescent samples at 0.75 OD (Sn 69.8%, Sp 89.5%). A relatively high (stringent) diagnostic cut-off value provides increased diagnostic accuracy with high sensitivity and specificity in the majority of cases, while lowering the cut-off runs the risk of false positivity. This study underlines the need for regional assessment of new diagnostic tests according to the level of endemicity of the disease given the high levels of residual or cross-reacting antibodies in the general population.

scholarly journals EVALUATION OF IGM ELISA, WEIL FELIX TEST AND INDIRECT IMMUNOFLUORESCENCE ASSAY IN THE DIAGNOSIS OF SCRUB TYPHUS.

2020 ◽  
pp. 1-4
Author(s):  
Pooja Raghunath
Keyword(s):  
Diagnostic Test ◽  
Scrub Typhus ◽  
Febrile Illness ◽  
High Sensitivity ◽  
Immunofluorescence Assay ◽  
Research Centre ◽  
Medical Sciences ◽  
Serological Tests ◽  
Igm Elisa ◽  
Highly Sensitive

Scrub typhus is an acute febrile illness caused by Orientia tsutsugamushi. There are reports of resurgence of scrub typhus in different parts of India including Kerala. Many cases go undiagnosed due to the lack of knowledge regarding the diagnostic test to be used. This study was undertaken at Pushpagiri Institute of Medical Sciences and Research Centre, Tiruvalla in the Department of Microbiology from January 2014 to September 2015, to assess the validity of various tests in diagnosing scrub typhus. A total of 94 samples were subjected to IgM ELISA, Weil Felix (WF) test and Indirect Immunouorescence assay(IFA). The agreement between ELISA, IFA and Weil Felix test was assessed by κ (kappa) coefcient of Cohen using SPSS version 17. The sensitivity and specicity of ELISA with respect to IFA was 100% and 94.67% respectively, and that of IFA with respect to ELISA was 82.61% and 100% respectively. The sensitivity and specicity of WF test with respect to ELISA was 43.48 and 100% respectively and that of WF test with respect to IFA was 52.63% and 100% respectively. Although IgM ELISA is highly sensitive, it cannot be relied upon as the sole diagnostic test due to high false positivity. WF test is not a sensitive test, but when positive it is rather specic. IFA has high sensitivity and specicity, but is unsuitable for moderately equipped laboratories. Hence, we suggest that scrub typhus could be diagnosed using a combination of IgM ELISA and WF test and these tests should be included in the panel of serological tests ordered for patients presenting with undifferentiated febrile illnesses.

scholarly journals Evaluation of a Genus Specific rGroEL 1-524 IgM-ELISA and Commercially ELISA Kits During Course of Leptospirosis in Thailand

2021 ◽  
Author(s):  
Santi Maneewatchararangsri ◽  
Galayanee Doungchawee ◽  
Thareerat Kalambaheti ◽  
Viravarn Luvira ◽  
Ngamphol Soonthornworasiri ◽  
...  
Keyword(s):  
Early Detection ◽  
Early Diagnosis ◽  
Screening Test ◽  
Scrub Typhus ◽  
Acute Infection ◽  
Febrile Illness ◽  
High Sensitivity ◽  
Elisa Assay ◽  
Igm Elisa ◽  
Post Onset

Abstract This work, we developed a genus-specific rGroEL1-524 IgM-ELISA assay for using as screening diagnosis of suspected leptospirosis among acute undifferentiated febrile illness patients during acute fever. Ddiagnostic accuracies of rGroEL1–524 IgM-ELISA, and commercial Panbio IgM-ELISA, and Virion-Serion Classic IgG-ELISA were evaluated with Thai 107 leptospirosis sera, and 189 controls, compared to reference culture and/or MAT methods. Sensitivities were 91.7%, 59.6%, and 17.7% for acute- infection, and were 97.1%, 54.8%, and 9.7% for early detection at 1-3 days post-onset of symptoms (DPO1-3), and the specificities were 87.5%, 86.6%, and 74.8% among controls, respectively. The rGroEL1-524 IgM-ELISA had high sensitivity, at 95.9% and 91.2% among culture and MAT negative cases. Impaired specificity on scrub typhus, possibly from antibody-cross reaction to ortholog GroEL. Commercial Panbio IgM-ELISA had sensitivities of 50%, 63.2%, and 89.9% compared with culture, MAT-negative and single MAT-positive cases whereas Virion-Serion IgG-ELISA provided sensitivities of 13.3%, 10.5% and 71.4%, respectively. A rGroEL1-524 IgM-ELISA could be useful as a screening test for early diagnosis. The performance of the commercial ELISA suggests the applicability of IgM-ELISA for diagnosis, while IgG-ELISA is useful for seroprevalence surveys. However, confirmation by reference tests is recommended.

scholarly journals Diagnostic evaluation of IgM ELISA and IgM Immunofluorescence assay for the diagnosis of Acute Scrub Typhus in central Nepal

2020 ◽  
Author(s):  
Rajendra Gautam ◽  
Keshab Parajuli ◽  
Tshokey Tshokey ◽  
John Stenos ◽  
Jeevan Bahadur Sherchand
Keyword(s):  
Likelihood Ratio ◽  
Predictive Value ◽  
Gold Standard ◽  
Scrub Typhus ◽  
Febrile Illness ◽  
Immunofluorescence Assay ◽  
Acute Febrile Illness ◽  
Central Nepal ◽  
Igm Elisa ◽  
Typhus Fever

Abstract Introduction Scrub typhus is an acute febrile illness caused by the obligate intracellular bacterium,Orientia tsutsugamushi. Given their affordability and ease of use, antibody based diagnostic assays can be important diagnostic tools for early detection of scrub typhus fever in resource poor countries like Nepal. 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 the InBios Scrub Typhus Detect™ Immunoglobulin M (IgM) ELISA and IgM Immunofluorescence assays in single serum sample at the time of admission. Methodology Study participants (1585 suspected cases), were enrolled based on acute febrile illness with suspected scrub typhus cases in central Nepal from April 2017 to March 2018. 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 (In Bios International, USA) and an in-house IgM IFA (Australian Rickettsial Reference Laboratory, Geelong, Australia. The IFA assay was performed with the Gilliam, Karp, Kato strains and O. chuto antigens following the ARRL protocol. Result Statistical analysis of ELISA IgM 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 The study indicated that the IgM ELISA has the sensitivity 84.0% (95% CI: 79.73%-87.68%) and specificity 94.82% (95% CI: 93.43%-95.99%). 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 with appropriate OD cut–off values may be the best alternative test and possible viable option for resource limited endemic countries like Nepal.

scholarly journals Diagnostic Accuracy of the InBios Scrub Typhus Detect Enzyme-Linked Immunoassay for the Detection of IgM Antibodies in Northern Thailand

2015 ◽  
Vol 23 (2) ◽  
pp. 148-154 ◽  
Author(s):  
Stuart D. Blacksell ◽  
Ampai Tanganuchitcharnchai ◽  
Pruksa Nawtaisong ◽  
Pacharee Kantipong ◽  
Achara Laongnualpanich ◽  
...  
Keyword(s):  
Diagnostic Accuracy ◽  
False Positive ◽  
Gold Standard ◽  
Latent Class ◽  
Scrub Typhus ◽  
Febrile Illness ◽  
Statistical Correlation ◽  
Immunofluorescence Assay ◽  
Enzyme Linked Immunosorbent Assay ◽  
Northern Thailand

ABSTRACTIn this study, we examined the diagnostic accuracy of the InBios Scrub Typhus Detect IgM enzyme-linked immunosorbent assay (ELISA) and determined the optimal diagnostic optical density (OD) cutoffs for screening and diagnostic applications based on prospectively collected, characterized samples from undifferentiated febrile illness patients in northern Thailand. Direct comparisons with the serological gold standard, indirect immunofluorescence assay (IFA), revealed strong statistical correlation of ELISA OD values and IFA IgM titers. Determination of the optimal ELISA cutoff for seroepidemiology or screening purposes compared to the corresponding IFA reciprocal titer of 400 as previously described for Thailand was 0.60 OD, which corresponded to a sensitivity (Sn) of 84% and a specificity (Sp) of 98%. The diagnostic performance against the improved and more-stringent scrub typhus infection criteria (STIC), correcting for low false-positive IFA titers, resulted in an Sn of 93% and an Sp of 91% at an ELISA cutoff of 0.5 OD. This diagnostic ELISA cutoff corresponds to IFA reciprocal titers of 1,600 to 3,200, which greatly reduces the false-positive rates associated with low-positive IFA titers. These data are in congruence with the recently improved serodiagnostic positivity criteria using the Bayesian latent class modeling approach. In summary, the InBios Scrub Typhus Detect IgM ELISA is affordable and easy-to-use, with adequate diagnostic accuracy for screening and diagnostic purposes, and should be considered an improved alternative to the gold standard IFA for acute diagnosis. For broader application, regional cutoff validation and antigenic composition for consistent diagnostic accuracy should be considered.

scholarly journals Serological evidence of human leptospirosis in patients with acute undifferentiated febrile illness from Uttarakhand, India: A pilot study

2019 ◽  
Vol 11 (01) ◽  
pp. 011-016
Author(s):  
Mohit Bhatia ◽  
Pradeep Kumar ◽  
Pratima Gupta ◽  
Puneet Kumar Gupta ◽  
Minakshi Dhar ◽  
...  
Keyword(s):  
Pilot Study ◽  
Scrub Typhus ◽  
Tertiary Care ◽  
Febrile Illness ◽  
Immunoglobulin M ◽  
Serological Evidence ◽  
Serum Samples ◽  
Malaria Parasites ◽  
Human Leptospirosis ◽  
Igm Elisa

Abstract CONTEXT: To the best of our knowledge, there are no reports of serological evidence of human leptospirosis from Uttarakhand state in India. AIMS: The aim of this study was to screen for serological evidence of leptospirosis in patients with acute undifferentiated febrile illness at a tertiary care teaching hospital in Uttarakhand. SETTINGS AND DESIGN: A pilot study was conducted from March to November 2017. SUBJECTS AND METHODS: Fifty-three adult patients who presented in Medicine outpatient Department with a history of fever of ≥7 up to 14 days duration with or without other associated symptoms such as a headache, rashes, myalgia, arthralgia, and conjunctival suffusion were enrolled in the study using convenience sampling technique. Blood samples of these patients were collected and subjected to peripheral smear examination for malaria parasites, dengue immunoglobulin M (IgM) immunochromatographic card test, IgM Typhidot, Leptospira and Scrub typhus IgM ELISA, respectively. Aerobic blood culture was performed in 24 cases. Relevant clinico-epidemiological details were obtained as per the pro forma formulated in accordance with the modified Faine’s criteria. STATISTICAL ANALYSIS USED: Descriptive statistics. RESULTS: The study population consisted of 50.94% of males and 49.06% of females with a mean age ± standard deviation of 34.2 ± 15.2 years. Fifty febrile patients had additional symptoms of which myalgia was the most common (81.1%) followed by arthralgia (22.6%). Peripheral smears of all patients were negative for malaria parasites. Dengue and Typhidot IgM positivity was observed in two and eight patients, respectively. Six and five patients were tested positive by leptospira and scrub typhus IgM ELISA, respectively. Salmonella Typhi was isolated from blood sample of only one patient. Serum samples of two patients showed dual positivity. All six leptospira seropositive patients satisfied modified Faine’s criteria. CONCLUSIONS: Leptospirosis is a seemingly unexplored infection in Uttarakhand and should be considered as a differential diagnosis in patients with acute undifferentiated febrile illness.

scholarly journals Diagnostic evaluation of IgM ELISA and IgM Immunofluorescence assay for the diagnosis of Acute Scrub Typhus in central Nepal

2019 ◽  
Author(s):  
Rajendra Gautam ◽  
Keshab Parajuli ◽  
Tshokey Tshokey ◽  
John Stenos ◽  
Jeevan Bahadur Sherchand
Keyword(s):  
Likelihood Ratio ◽  
Predictive Value ◽  
Gold Standard ◽  
Scrub Typhus ◽  
Febrile Illness ◽  
Immunofluorescence Assay ◽  
Acute Febrile Illness ◽  
Central Nepal ◽  
Igm Elisa ◽  
Typhus Fever

Abstract Introduction Scrub typhus is an acute febrile illness caused by the obligate intracellular bacterium,Orientia tsutsugamushi. Given their affordability and ease of use, antibody based diagnostic assays can be important diagnostic tools for early detection of scrub typhus fever in resource poor countries like Nepal. 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 the InBios Scrub Typhus Detect™ Immunoglobulin M (IgM) ELISA and IgM Immunofluorescence assays in single serum sample at the time of admission. Methodology Study participants (1585 suspected cases), were enrolled based on acute febrile illness with suspected scrub typhus cases in central Nepal from April 2017 to March 2018. 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 (In Bios International, USA) and an in-house IgM IFA (Australian Rickettsial Reference Laboratory, Geelong, Australia. The IFA assay was performed with the Gilliam, Karp, Kato strains and O. chuto antigens following the ARRL protocol. Result Statistical analysis of ELISA IgM 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 The study indicated that the IgM ELISA has the sensitivity 84.0% (95% CI: 79.73%-87.68%) and specificity 94.82% (95% CI: 93.43%-95.99%). 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 with appropriate OD cut–off values may be the best alternative test and possible viable option for resource limited endemic countries like Nepal.

scholarly journals Evaluation of a genus-specific rGroEL1-524 IgM-ELISA and commercial ELISA kits during the course of leptospirosis in Thailand

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Santi Maneewatchararangsri ◽  
Galayanee Doungchawee ◽  
Thareerat Kalambaheti ◽  
Viravarn Luvira ◽  
Ngamphol Soonthornworasiri ◽  
...  
Keyword(s):  
Early Diagnosis ◽  
Screening Test ◽  
Scrub Typhus ◽  
Acute Infection ◽  
Febrile Illness ◽  
High Sensitivity ◽  
Elisa Assay ◽  
Igm Elisa ◽  
Culture Positive ◽  
Post Onset

AbstractIn the present study, we developed a genus-specific rGroEL1-524 IgM-ELISA assay for use in screening diagnosis of suspected leptospirosis among acute undifferentiated febrile illness patients during acute fever. The diagnostic accuracies of the rGroEL1–524 IgM-ELISA, commercial Panbio IgM-ELISA, and Virion-Serion Classic IgG-ELISA were evaluated using 133 Thai leptospirosis sera and 210 controls. Sensitivities were 91.7%, 59.6%, and 17.7% for acute infection, and the specificities were 92.6%, 90.2%, and 88.3% for the non-leptospirosis control, respectively. The rGroEL1-524 IgM-ELISA had high sensitivity, at 92.3% and 91.7%, among culture-positive and MAT-negative cases at 1–3 days post-onset of symptoms (DPO1–3), respectively. Impaired specificity on scrub typhus was found, possibly from antibody cross-reaction to ortholog GroEL. Commercial Panbio IgM-ELISA had sensitivities at DPO1–3 of 30.8% and 41.7% for culture-positive and MAT-negative cases whereas Virion-Serion IgG-ELISA showed sensitivities of 5.9% and 13.3%, respectively. The rGroEL1-524 IgM-ELISA could be useful as a screening test for early diagnosis. The performance of the commercial ELISA suggests the applicability of IgM-ELISA for diagnosis, while IgG-ELISA is useful for seroprevalence surveys. However, confirmation by reference tests is recommended.

scholarly journals Diagnostic evaluation of IgM ELISA and IgM Immunofluorescence assay for the diagnosis of Acute Scrub Typhus in central Nepal

2019 ◽  
Author(s):  
Rajendra Gautam ◽  
Keshab Parajuli ◽  
Tshokey Tshokey ◽  
John Stenos ◽  
Jeevan Bahadur Sherchand
Keyword(s):  
Likelihood Ratio ◽  
Predictive Value ◽  
Gold Standard ◽  
Scrub Typhus ◽  
Febrile Illness ◽  
Immunofluorescence Assay ◽  
Acute Febrile Illness ◽  
Central Nepal ◽  
Igm Elisa ◽  
Typhus Fever

Abstract Introduction Scrub typhus is an acute febrile illness caused by the obligate intracellular bacterium,Orientia tsutsugamushi. Given their affordability and ease of use, antibody based diagnostic assays can be important diagnostic tools for early detection of scrub typhus fever in resource poor countries like Nepal. 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 the InBios Scrub Typhus Detect™ Immunoglobulin M (IgM) ELISA and IgM Immunofluorescence assays in single serum sample at the time of admission. Methodology Study participants (1585 suspected cases), were enrolled based on acute febrile illness with suspected scrub typhus cases in central Nepal from April 2017 to March 2018. 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 (In Bios International, USA) and an in-house IgM IFA (Australian Rickettsial Reference Laboratory, Geelong, Australia. The IFA assay was performed with the Gilliam, Karp, Kato strains and O. chuto antigens following the ARRL protocol. Result Statistical analysis of ELISA IgM 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 The study indicated that the IgM ELISA has the sensitivity 84.0% (95% CI: 79.73%-87.68%) and specificity 94.82% (95% CI: 93.43%-95.99%). 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 with appropriate OD cut–off values may be the best alternative test and possible viable option for resource limited endemic countries like Nepal.

scholarly journals Diagnostic evaluation of IgM ELISA and IgM Immunofluorescence assay for the diagnosis of Acute Scrub Typhus in central Nepal

2019 ◽  
Author(s):  
Rajendra Gautam ◽  
Keshab Parajuli ◽  
John Stenos ◽  
Tshokey Tshokey ◽  
Jeevan Bahadur Sherchand
Keyword(s):  
Likelihood Ratio ◽  
Predictive Value ◽  
Gold Standard ◽  
Scrub Typhus ◽  
Febrile Illness ◽  
Immunofluorescence Assay ◽  
Acute Febrile Illness ◽  
Central Nepal ◽  
Igm Elisa ◽  
Typhus Fever

Abstract Introduction Scrub typhus is an acute febrile illness caused by the obligate intracellular bacterium,Orientia tsutsugamushi. Given their affordability and ease of use, antibody based diagnostic assays can be important diagnostic tools for early detection of scrub typhus fever in resource poor countries like Nepal. 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 the InBios Scrub Typhus Detect™ Immunoglobulin M (IgM) ELISA and IgM Immunofluorescence assays in single serum sample at the time of admission. Methodology Study participants (1585 suspected cases), were enrolled based on acute febrile illness with suspected scrub typhus cases in central Nepal from April 2017 to March 2018. 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 (In Bios International, USA) and an in-house IgM IFA (Australian Rickettsial Reference Laboratory, Geelong, Australia. The IFA assay was performed with the Gilliam, Karp, Kato strains and O. chuto antigens following the ARRL protocol. Result Statistical analysis of ELISA IgM 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 The study indicated that the IgM ELISA has the sensitivity 84.0% (95% CI: 79.73%-87.68%) and specificity 94.82% (95% CI: 93.43%-95.99%). 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 with appropriate OD cut–off values may be the best alternative test and possible viable option for resource limited endemic countries like Nepal.

scholarly journals Diagnostic evaluation of IgM ELISA and IgM Immunofluorescence assay for the diagnosis of Acute Scrub Typhus in central Nepal

2019 ◽  
Author(s):  
Rajendra Gautam ◽  
Keshab Parajuli ◽  
Tshokey Tshokey ◽  
John Stenos ◽  
Jeevan Bahadur Sherchand
Keyword(s):  
Likelihood Ratio ◽  
Predictive Value ◽  
Gold Standard ◽  
Scrub Typhus ◽  
Febrile Illness ◽  
Immunofluorescence Assay ◽  
Acute Febrile Illness ◽  
Central Nepal ◽  
Igm Elisa ◽  
Typhus Fever

Abstract Introduction Scrub typhus is an acute febrile illness caused by the obligate intracellular bacterium,Orientia tsutsugamushi. Given their affordability and ease of use, antibody based diagnostic assays can be important diagnostic tools for early detection of scrub typhus fever in resource poor countries like Nepal. 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 the InBios Scrub Typhus Detect™ Immunoglobulin M (IgM) ELISA and IgM Immunofluorescence assays in single serum sample at the time of admission. Methodology Study participants (1585 suspected cases), were enrolled based on acute febrile illness with suspected scrub typhus cases in central Nepal from April 2017 to March 2018. 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 (In Bios International, USA) and an in-house IgM IFA (Australian Rickettsial Reference Laboratory, Geelong, Australia. The IFA assay was performed with the Gilliam, Karp, Kato strains and O. chuto antigens following the ARRL protocol. Result Statistical analysis of ELISA IgM 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 The study indicated that the IgM ELISA has the sensitivity 84.0% (95% CI: 79.73%-87.68%) and specificity 94.82% (95% CI: 93.43%-95.99%). 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 with appropriate OD cut–off values may be the best alternative test and possible viable option for resource limited endemic countries like Nepal.

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