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Sexually Transmitted Diseases > Publications > Report
of the Genital Herpes Prevention Consultants Meeting May 5-6, 1998
Report of the Genital Herpes Prevention Consultants Meeting May 5-6, 1998
1. Performance and Uses of Type-Specific HSV Serological TestsClinical recognition and diagnosis of genital herpes are insensitive due to the frequency of subclinical infection and the insensitivity of virologic testing, especially for healing lesions, and the inability of heretofore widely available serological tests for HSV to differentiate the serological responses to HSV-1 and HSV-2. Several truly type-specific serological tests have been developed, most based on antibody to HSV glycoproteins G1 and G2, which have antigenic specificities to HSV-1 and HSV-2, respectively. Type-specific assays have been available in research settings for about 15 years, but only recently have tests been developed for the commercial market. A. Availability and Cost Selected tests currently available in research and commercial settings are listed in Appendix 3. The Western blot has been offered commercially and is widely accepted as the most accurate overall assay but is too cumbersome and expensive for routine use ($95 at the University of Washington), although it is likely to retain a role as a confirmatory assay. The HSV gG type-specific ELISA (Gull Laboratories) and the POCkit-HSV-2 test (Diagnology) are in late stages of clinical testing and are likely to be commercially available in the near future. Their costs are uncertain, but the cost of materials and labor to perform them are likely to be in the range of $8.00 to $40.00 per assay. A few other tests are in various stages of commercial development, whereas others are likely to be available only on a limited basis as research tools. B. Performance The Western blot detects antibodies to a large number of HSV antigens and has been shown to have both sensitivity and specificity >99% for symptomatic infections established >6 months.* Most other assays detect antibody to single antigens and compared to Western blot are at present less sensitive and/or less specific (Appendix 3). All assays have variable and relatively low sensitivities for infection <6 months’ duration. Substantial discussion addressed the newer tests’ specificity, approximating 97-99% compared with Western blot, which has important implications for the use and interpretation of test results in individual patients. For example, in a population with 10% prevalence (as might be expected in some screening settings, such as teen clinics) a test with 95% sensitivity and 98% specificity has a positive predictive value (PPV) of 84%, corresponding to an unacceptable 16% rate of false positive results. Thus, serious concerns were raised about the utility of the newer assays as single tests for screening. A possible approach would be to use a sequential testing scheme, with re-testing all positives with a second assay, a strategy that probably would substantially increase for the cost of screening programs. However, in a population with a 50% prevalence rate the PPV rises to 98%, which may be acceptable for some uses, such as diagnosis of genital ulcer disease or evaluating the sex partners of persons with genital herpes. Although concerns have been raised that some infected persons may lose antibody to HSV-2 over time ("seroreversion"), there was consensus that this phenomenon is due not to loss of antibody but to a lower sensitivity of antibody detection for some assays, which are operating at or near their limits of detection. However, no studies have determined the natural course of seroreactivity in persons with longstanding subclinical infection or in never-symptomatic infected persons. There was broad consensus that type-specific serological tests for HSV are useful in the diagnosis of genital ulcer disease (e.g., for patients with recurrent genital lesions in whom viral isolation is impractical or unsuccessful) and for counseling, and that all clinicians who manage patients with STD or at risk should have access to such assays when they become generally available at reasonable cost. Nevertheless, several unknowns must be resolved before the full scope of serological testing is known and its role in genital herpes prevention fully defined. These include the "real world" performance of the newer assays, outside research settings; performance of all assays in chronic, subclinical infection, including the natural history of seroreactivity in subclinically infected persons; and the psychological and behavioral responses to being informed of a reactive test, especially in persons with neither clinical nor epidemiologic histories to suggest genital herpes. It was recognized that many patients seeking STD clinical services assume that evaluation routinely includes assessment for all common STDs, including herpes, but that almost no STD clinics and few other providers of STD clinical services routinely offer this service. However, quantitative data are lacking. C. Recommendations
Page last modified: September 18, 1998 Page last reviewed: September 18, 1998 Historical Document Content Source: Division of STD Prevention, National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention |
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