Updates in Immunoassays: Virology

Extract

The rapid identification of viral infectious agents has always been a challenge to clinical microbiologists. The long standing gold standard for diagnosing viruses is the cell culture,¹ however most cultures take up to 7 days for an accurate identification.² This turnaround time is unacceptable in healthcare where a rapid diagnosis and appropriate treatment is essential for positive patient outcomes and reduced hospital stays. With emerging technology and the variety of molecular platforms available, identifying viruses can be achieved in a matter of hours.^3,4 Although nucleic-acid amplification tests are highly sensitive and specific, “the performance of molecular assays can vary significantly due to nucleic acid extraction methods, primer and probe design, amplification and detection technologies, instrumentation, and technical expertise.”⁴ In recent years some of the self-contained molecular systems such as the GeneXpert System and SmartCycler System by Cepheid have eliminated these issues.⁵ Although many laboratories have taken on molecular assays for identifying viruses, immunoassays are still widely used in the identification process due to the rapid, sensitive, and accurate results they produce, not to mention their cost effectiveness and ease of use.

Rapid direct antigen testing and immunofluorescent assays are widely used in the clinical laboratory; however, controversy exists regarding the sensitivity and specificity of some of the methodologies used for viral detection. In a recent review published in CAP Today, several invited speakers at the Association for Molecular Pathology's 2011 conference commented on the use of molecular platforms in identifying viruses and compared the sensitivity and specificity with rapid direct…

ABBREVIATIONS: Ag/Ab = antigen/antibody; CAP - College of American Pathologists; CLIA - chemiluminescent immunoassay; CMIA - chemiluminescent microparticle immunoassay; CMV - cytomegalovirus; EBV - Epstein-Barr virus; EIA - enzyme immunoassay; ELFA - enzyme-linked fluorescent assay; ELISA - enzyme-linked immunosorbent assay; FDA - Food and Drug Administration; GS - Genetic Systems; HBV - hepatitis B virus; HCV - hepatitis C virus; HIV - human immunodeficiency virus; HSV - Herpes simplex virus; IFA - immunofluorescent assay; MEIA - microparticle enzyme immunoassay; RSV - respiratory syncytial virus; VZV - Varicella zoster virus.