Image: The dengue virus (DENV) Detect IgM Capture ELISA from InBios (Photo courtesy of Inbios).
Researchers have now reported results from a first evaluation of the FDA-cleared assay for diagnosis of dengue virus infection in patients with suggestive clinical symptoms.
A study from the laboratory of Prof. Vivek R. Nerurkar at the University of Hawaii at Manoa (UHM; Honolulu, Hawaii, USA) provides the first independently funded evaluation of the InBios "DENV Detect IgM Capture ELISA", a rapid in vitro assay based on technology patented by the US Centers for Disease Control and Prevention (CDC; Atlanta, GA, USA). The assay, produced by Inbios International, Inc. (Seattle, WA, USA), is currently the only commercially available dengue infection assay cleared by the the US Food and Drug Administration (FDA; Silver Spring, MD, USA).
Diagnostic testing for dengue virus (DENV) infection is often time-consuming and complicated. The current study provides a comparative evaluation of the rapid (about five hours) InBios assay and a 2–3 day in-house "gold-standard" assay, and discusses some of the complicating factors. Well-characterized clinical serum samples obtained from 79 dengue-infected patients or suspected cases were performance-tested for qualitative detection of anti-DENV IgM antibodies, mainly in terms of sensitivity and specificity. The serum samples were collected from Hawaii, Vietnam, Niue, Singapore, and American Samoa, where dengue outbreaks have occurred in the past. Samples with equivocal results were repeated in duplicate, and samples that remained equivocal were further examined (e.g., using plaque reduction neutralization test (PRNT) where sufficient sample serum was available). Inclusion of positive as well as negative antigens was critical for interpretation of the results, as they detect background, nonspecific reactivity.
Sensitivity and specificity of InBios ELISA compared to the in-house "gold standard" ELISA were 92% and 94%, respectively. Out of the 79 serum samples tested, 22 samples were positive and 50 samples were negative by using both assays. Levels of agreement as defined by kappa values were also determined and the two assays showed near perfect agreement (κ = 0.87).
Overall, despite the relatively minor limitations of the study itself, the results indicate that the more rapid InBios DENV Detect IgM Capture ELISA is a reliable, sensitive, and specific serological test for detection of acute or recent dengue infections. It can also be used by public health laboratories for rapid confirmation of dengue cases during dengue outbreaks. Both tests show some cross-reactivity with West Nile and other closely related viruses and this must be considered, particularly when working in geographic regions where multiple flaviviruses co-circulate.
This study by Namekar M., et al. was published online ahead of print July 3, 2013, in the Journal of Clinical Microbiology.
UHM Dengue Test Publication Link
University of Hawaii at Manoa