The Need for Geographic Location Specific Optical Density Cut-offs for IgM ELISA Serology to Diagnose Scrub Typhus in Children

Scrub typhus (Orientia tsutsugamushi), is a strict intracellular bacterium which is reported to be a recent threat to parts of southern India. There is re-emergence of scrub typhus during the past few years in Chennai. Scrub typhus is an acute febrile illness which generally causes non-specific symptoms and signs. The clinical manifestations of this disease range from sub-clinical disease to organ failure to fatal disease. This study documents our laboratory experience in diagnosis of scrub typhus in patients with fever and suspected clinical symptoms of scrub typhus infection for a period of two years from April 2014 to April 2016 using immunochromatography and IgM ELISA methods. The study was conducted on 648 patients out of whom 188 patients were found to be positive for scrub typhus. Results also showed that pediatric (0 -12 years) and young adults (20 – 39 years) were more exposed to scrub typhus infection and female patients were more infected compared to male. The study also showed that the rate of infection was higher between September to February which also suggested that the infection rate is proportional to the climatic condition. Statistical analysis showed that the mean age of the patients in this study was 37.6, standard deviation was 18.97, CV % was 50.45.

Download Full-text

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

Tropical Medicine and Infectious Disease ◽

10.3390/tropicalmed3030095 ◽

2018 ◽

Vol 3 (3) ◽

pp. 95 ◽

Cited By ~ 7

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.

Download Full-text

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

10.21203/rs.3.rs-352195/v1 ◽

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.

Download Full-text

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

10.21203/rs.2.10024/v5 ◽

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.

Download Full-text

Spectrum of Multiorgan Dysfunction in Scrub Typhus Infection

Journal of Tropical Pediatrics ◽

10.1093/tropej/fmab074 ◽

2021 ◽

Vol 67 (4) ◽

Author(s):

Vidushi Mahajan ◽

Vishal Guglani ◽

Nidhi Singla ◽

Jagdish Chander

Keyword(s):

Pressure Support ◽

Distress Syndrome ◽

Scrub Typhus ◽

Pediatric Emergency ◽

University Teaching ◽

Positive Pressure ◽

Mortality And Morbidity ◽

Multiorgan Dysfunction ◽

Igm Elisa ◽

Systemic Manifestations

Abstract Objectives We planned this study to determine the clinical spectrum and compare incidence of multiorgan dysfunction in children hospitalized with scrub typhus with other etiologies of tropical fever. Design Prospective cohort study. Setting Pediatric emergency and PICU services of a university teaching hospital situated in the sub-Himalayan region. Patient Children aged 2 months to 14 years with acute undifferentiated fever of more than 5 days. Interventions Detailed fever workup was performed in all children. We compared scrub typhus IgM positive children (cases) with remaining febrile children who were negative for scrub IgM assay (controls) for mortality and morbidity. Main results We enrolled 224 febrile children; 76 children (34%) were positive for scrub typhus IgM ELISA. Scrub typhus group had a significantly higher incidence of multiorgan dysfunction [OR 3.5 (95% CI 2.0–6.3); p < 0.001] as compared to non-scrub typhus group requiring supportive care. The incidence of altered sensorium [OR 8.8 (95% CI 3.1–24.9)], seizures [OR 3.0 (95% CI 1.1–8.3)], acute respiratory distress syndrome [OR 17.1 (95% CI 2.1–140.1)], acute renal failure (5% vs. 0%), meningitis [OR 6.2 (95% CI 1.2–31.6)], thrombocytopenia [OR 2.8 (95% CI 1.5–5.1)], transaminitis [OR 2.7 (95% CI 1.6–4.8)], requirement of oxygen [OR 17.8 (95% CI 4.0–80.3)], positive pressure support [OR 3.7 (95% CI 1.2–10.5)] and shock requiring inotropes [OR 3.0 (95% CI 1.3–6.7)] was significantly higher in scrub typhus group as compared to the non-scrub typhus group (Table 1). Conclusions Pediatric scrub typhus who were hospitalized had severe systemic manifestations when compared to other causes of fever.

Download Full-text

Clinical presentation of scrub typhus during a major outbreak in central Nepal

Asian Journal of Medical Sciences ◽

10.3126/ajms.v8i4.17163 ◽

2017 ◽

Vol 8 (4) ◽

pp. 27-31 ◽

Cited By ~ 5

Author(s):

Arun Sedhain ◽

Gandhi R. Bhattarai

Keyword(s):

Acute Kidney Injury ◽

Scrub Typhus ◽

Clinical Manifestations ◽

Kidney Injury ◽

Continuous Variables ◽

Neurologic Manifestation ◽

Igm Elisa ◽

Clinical Presentations ◽

Tertiary Teaching ◽

Major Outbreak

Background: Scrub typhus, an emerging rickettsial disease caused by the organism Orientiatsutsugamushi, is associated with multi-organ involvement. We prospectively studied the clinical manifestations of the disease during a major outbreak in central part of Nepal.Aims and Objective: This study was carried out with an aim to analyze the clinical presentations, laboratory parameters, complications and outcomes of scrub typhus.Materials and Methods: A prospective observational study was conducted in the Department of Medicine in a tertiary teaching hospital. A total of 1398 patients admitted with acute febrile illness were subjected for Scrub Typhus Detect™ IgM ELISA test, among which 502 (35.90%) patients tested positive and were included in the study. Acute kidney injury was defined according to KDIGO guideline. Statistical analysis was done with SAS University Studio package using t-test for continuous variables and chi-square test for categorical variables.Results: Mean age of the patients was 30.37±18.81 years with 26.29% in the pediatric age group (<14 years). Females comprised of 55.98% of the patients. Majority (97.98%) of the patients were seen between July to November. Clinical presentations in the descending order of frequency were anorexia (55.18%), headache (53.39%), lymphadenopathy (15.73%), jaundice (13.35) and eschar (6.57%). Mean scrub typhus IgM ELISA value was 2.17. Leukocytosis was seen in 5.78% and thrombocytopenia in 66.73% of patients. Transaminitis was found in 80.68% of patients. Urinary abnormalities were recorded in 42.3% of patients. Acute kidney injury (AKI) was seen in 35.8% of patients followed by acute respiratory distress syndrome (24.1%), pneumonia (22.1%), shock (14.74%), neurologic manifestation (6.37%) and cardiac manifestations (4.38%). ICU admission was required for 18.73% of patients and 8.57% required ventilator support. Mortality rate was 1.79%.Conclusion: Scrub typhus, being an emerging vector borne infectious disease in Nepalese context, is associated with multiple organ involvement.Asian Journal of Medical Sciences Vol.8(4) 2017 27-31

Download Full-text