By David Kilpatrick, PhD and Abbas Vafai, PhD
INTRODUCTION: There are several commercial immunoassays for HSV on the market (Western blot, Dot blot or standard ELISA assays). Of these, the University of Washington Western blot assay (UW-WB) is considered the “gold standard” for assays to detect Herpes virus antibodies in patient sera1University of Washington Western blot. https://depts.washington.edu/. While this FDA approved assay is considered to be very accurate, a second confirmatory assay is often preferred as most patients are unaware of their genital Herpes status2Ashley-Morrow, Rhoda, and David Friedrich, 2003. The inaccuracy of Certain Commercial Enzyme Immunoassays in Diagnosing Genital Infections with Herpes Simplex Virus Types 1 and 2. Am J Clin Pathol, 120:839-844.. False-positive results can bring emotional stress to the patient, and for this reason, a second test is often requested for a confirmatory result3CDC 2015. Sexually Transmitted Diseases Treatment Guidelines. https:// www.cdc.gov/ .
DISCUSSION: Several reports have analyzed available commercial assays in the past. One review compared thirteen available commercial immunoassays for HSV-24van Dyck, et al., 2004. Performance of Commercially Available Enzyme Immunoassays for Detection of Antibodies against Herpes Simplex Virus Type 2 in African Populations. J. Clin. Micro. 42(7):2961-2965.. Test samples were first compared to monoclonal antibody (MAb) enzyme immunoassays (EIA) from the Central Public Health Lab, London, UK. The discordant assays and the three best assays were compared to the Western blot assay from the University of Washington. Test sensitivities from 86% to 100%, while the specificity ranged from 47-99%. The tests which performed the best were the Gull Premier EIA (sensitivity, 86.7%; specificity 97.6%), and the Kalon Biological (sensitivity, 92.3%; specificity, 97.7%) tests. In another more recent article Patel et. al.,5Patel, et al., Precision of the Kalon Herpes Simplex Virus Type 2 IgG ELISA: an international inter-laboratory assessment. BMC Infectious Diseases 15:398-406. found that the Kalon assay was reliable, stand-alone, on-site assay for detecting HSV-2 IgG antibodies. While the University of Washington HSC Western blot (UW-WB) is expensive and technically difficult for screening and clinical trials, other commercial assays such as the Kalon (which is not yet FDA approved) and the FDA-cleared Focus HerpeSelct-2 IgG ELISA offer reliable assays for use in secondary research. Both of these assays have optimal accuracy in industrialized countries, while their performance on sera from developing countries has varied6Biraro, et al., 2011. Performance of commercial Herpes Simplex Virus Type-2 antibody tests using serum samples from Sub-Sahara Africa: a systematic review and meta-analysis. Sex Transm. Dis. 38(2):140-147.. These investigators found that the high false positivity rate of the HerpeSelect assay was a challenge in African sera. Poor specificity of this test in HIV-1 seropositive patients shows a need for additional commercially available for HSV-2 detection in these populations. Additional economically feasible, reliable assays which are not as technically challenging, should be welcomed in the market place.
CONCLUSION: Commercial tests for the detection of HSV are often unreliable, especially for those with a “low positive” score. For this reason, a report from the American Sexual Health Association in 2017 states that improved Herpes diagnostic tests are needed. It was reported that nearly 50% of commercial tests indicating an HSV-2 infection were inaccurate7Agyemang, et al, 2017. Performance of Commercial Enzyme-linked Immunoassays for Diagnosis of Herpes Simplex Virus-1 and Herpes Simplex Virus-2 Infection in a Clinical Setting. Sexually Transmitted Diseases, 44-12:763-767..
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