Diagnostic performance of the equine IgM capture ELISA for serodiagnosis of West Nile virus infection.
Abstract: The objectives of these studies were to assess the diagnostic performance (sensitivity and specificity) of the IgM capture enzyme-linked immunosorbent assay (ELISA; MAC) for diagnosis of West Nile (WN) virus in horses and to examine the performance of this test by using different criteria for seropositivity. A total of 36 horses classified as WN virus infected (group 1) and 383 horses from 4 subpopulations of hoses classified as noninfected (groups 2, 3, 4, and 5) were used in the study. The sensitivity (proportion of infected horses that tested positive for WN virus IgM antibodies) and specificity (proportion of noninfected horses that tested negative) were calculated at different cutoff points by using receiver operating curve (ROC) analysis. Using a selected cutoff point = 2.0, the sensitivity and specificity of the MAC were 91.7 and 99.2%, respectively. The area under the ROC curve = 0.95 (95% confidence interval [CI], 0.89 to 1.0), suggesting that the MAC is a useful tool for diagnosis of recent WN virus exposure in horses. In fulfillment of the 2nd objective, 2 other indices were developed and these indices approached 1.0 for the AUC with smaller 95% CIs. These indices were then used to test 602 additional diagnostic samples submitted from suspect horses between 2002 and 2004. Using the standard cutoff, 194 (32%) of the horses were interpreted as positive. Utilizing newly predicted cutoff criteria from each index, additional horses were identified as positive. In conclusion, the MAC as used for identification of WN virus-diseased horses undergoing recent exposure performs reliably at the standard cutoff for seropositivity. A negative test might not completely rule out WN virus disease, but horses that test negative were most likely not exposed to WNV. Performance of the test can be further improved by investigation of other indexes of seropositivity.
Publication Date: 2006-06-01 PubMed ID: 16734097DOI: 10.1892/0891-6640(2006)20[608:dpotei]2.0.co;2Google Scholar: Lookup
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- Evaluation Study
- Journal Article
- Research Support
- Non-U.S. Gov't
- Antibodies
- Clinical Study
- Diagnosis
- Diagnostic Technique
- Disease Diagnosis
- Disease Surveillance
- Enzyme-Linked Immunosorbent Assay (ELISA)
- Epidemiology
- Equine Health
- Horses
- Immunoglobulin M
- Infection
- Infectious Disease
- Laboratory Methods
- Sensitivity and Specificity
- Serodiagnosis
- Seroprevalence
- Veterinary Medicine
- Virus
- West Nile Virus
Summary
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The research investigated the diagnostic accuracy and usefulness of the IgM capture enzyme-linked immunosorbent assay (MAC-ELISA) in diagnosing West Nile virus in horses. The researchers found that this test has a high sensitivity and specificity at a selected cutoff point, indicating it is a reliable tool for diagnosing recent West Nile virus exposure.
The Study and Methods
- The primary focus of the research was to assess the diagnostic performance – sensitivity, and specificity – of the Immunoglobulin M (IgM) Capture Enzyme-Linked Immunosorbent Assay (ELISA), also known as MAC, for the diagnosis of West Nile (WN) virus in horses.
- The researchers used a total of 36 horses known to be infected with WN Virus (Group 1) and 383 non-infected horses from four different subpopulations (Groups 2, 3, 4, and 5) for this study.
- The sensitivity and specificity of the MAC-ELISA test were calculated at different cutoff points using a method called Receiver Operating Curve (ROC) analysis.
Results of the Research
- The results demonstrated the MAC-ELISA, when the cutoff point was set to 2.0, had a sensitivity of 91.7% (indicating the percentage of infected horses that tested positive for WN Virus IgM antibodies) and a specificity of 99.2% (signifying the percentage of non-infected horses that tested negative).
- The area under the ROC curve was 0.95 (indicating a high accuracy rate), affirming the effectiveness of the MAC-ELISA as a tool for diagnosing recent WN Virus exposure in horses.
Validity of the Tests’ Criteria
- The researchers also developed two more indices for a comprehensive assessment of the testing criteria. These indices were found to have values close to 1.0 for the Area Under Curve (AUC) with smaller 95% Confidence Intervals (CIs), suggesting a significant likelihood of the results being valid in the entire population.
- When these indices were used to test 602 more samples from suspected horses, additional horses infected with WN Virus were identified.
Conclusions Drawn
- Overall, the MAC-ELISA was found to be reliable at the selected cutoff point in diagnosing horses recently exposed to WN Virus.
- The findings suggest that a negative test might not entirely rule out WN Virus infection although horses testing negative are most likely not exposed to the virus.
- Additionally, the study concludes that the performance of the MAC ELISA for serodiagnosis of West Nile virus can potentially be improved further by exploring other indices of seropositivity.
Cite This Article
APA
Long MT, Jeter W, Hernandez J, Sellon DC, Gosche D, Gillis K, Bille E, Gibbs EP.
(2006).
Diagnostic performance of the equine IgM capture ELISA for serodiagnosis of West Nile virus infection.
J Vet Intern Med, 20(3), 608-613.
https://doi.org/10.1892/0891-6640(2006)20[608:dpotei]2.0.co;2 Publication
Researcher Affiliations
- Large Animal Clinical Sciences, University of Florida, Gainesville 32511-0136, USA. longm@mail.vetmed.ufl.edu
MeSH Terms
- Animals
- Antibodies, Viral / immunology
- Case-Control Studies
- Enzyme-Linked Immunosorbent Assay / veterinary
- Horse Diseases / blood
- Horse Diseases / diagnosis
- Horse Diseases / virology
- Horses
- Immunoglobulin M / immunology
- Predictive Value of Tests
- ROC Curve
- Sensitivity and Specificity
- Serologic Tests / veterinary
- West Nile Fever / diagnosis
- West Nile Fever / veterinary
- West Nile virus / immunology
Citations
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