Guidelines for the laboratory diagnosis of genital herpes in eastern European countries

Introduction

During the past 20 years, genital herpes has emerged as one of the most prevalent sexually transmitted infections (STIs). However, data on morbidity due to genital herpes infections in eastern European countries is scarce and their reliability doubtful owing to the lack of validation studies for the diagnostic tests used. The World Health Organization (WHO) has estimated a prevalence of herpes simplex virus type 2 (HSV-2) infection of 29 million cases in men and 12.3 million cases in women in eastern Europe and central Asia in 2003 [1]. The international classification of diseases caused by herpes virus (anogenital) [2] is presented in Table 1.

Table 1. International classification of diseases: anogenital herpes virus infection

Human herpes simplex virus infections can be caused by HSV-1 or by HSV-2. In general, infections caused by HSV-1 manifest above the neck and are acquired as a result of close contact with infected persons, usually in childhood. In contrast, the lesions of infections caused by HSV-2 are usually located below the waist and are usually acquired as a result of sexual contact with infected persons later in life. Unfortunately, the differentiation of HSV-1 from HSV-2 based on anatomical site of infection is not absolute, since genital herpes may frequently be caused by HSV-1 as a result of oro-genital sexual practices and vice versa. The lesions and natural history of the resulting illnesses are very similar. However, because HSV-2 is almost always associated with genital disease, whereas HSV-1 is associated with both oro-pharyngeal and genital disease, there is often considerable stigma associated with HSV-2 infection. Acquisition of HSV-1 usually results in lesions of the oro-pharynx and around the mouth and on the lips and chin. Occasionally the eyes are affected. Sexual transmission of HSV most often produces infection of the genital mucosa, genital skin (penile and labial) and the perigenital region. Virus from genital secretions can also infect other areas, including the eyes and oro-pharynx and rectal mucosa [3,4].

Primary herpetic infection, i.e. when an HSV-seronegative person acquires HSV-1 or HSV-2, is usually the most severe manifestation of infection. Children may develop severe oro-pharyngitis following primary exposure to HSV-1. This episode resolves spontaneously, but recurrences may occur as a result of reactivation of the infection that has become latent but persists in the cervical ganglia. Similarly, if an individual has not been exposed to HSV-1 in childhood, he or she may develop severe genital lesions following sexual exposure to HSV-2 later in life. As with HSV-1 infections, primary HSV-2 infections resolve spontaneously but recurrences are likely to occur as a result of reactivation of latent infection that has been established in the sacral ganglia. In cases of initial, non-primary infection, i.e. when a person with antibodies to HSV-1 subsequently acquires HSV-2, the genital infection is less severe, but is also associated with recurrences. In most cases of genital herpes (80–90%) the disease progresses subclinically, but may become symptomatic at any time [5,6]. The incubation period of both HSV-1 and HSV-2 is usually from two to 10 days (up to four weeks). Therefore, the first episode may indicate either recent or long-lasting infection [7].

Recurrent herpetic infection is associated with reactivation of the virus. The recurrences arise with different frequency: from once every few years to several times per month. The localisation of the primary and recurrent lesions usually coincides. Both oral and genital herpes are manifested by acute recurrences followed by varying periods of latency, when the virus remains in a non-multiplying episomal form in the nuclei of the neurons in the ganglia. Classically, each episode or recurrence is characterised by a patch of redness at the site of the recurrence, followed by a localised papular then vesicular rash. The vesicles contain a clear fluid that contains many thousands of infectious viral particles. These vesicles burst, forming shallow ulcers or erosions that eventually crust and heal spontaneously without leaving scars. These episodes usually last less than 10 days, but may be prolonged as a result of secondary bacterial infection or immunosuppression.

Genital and oral herpes are life-long infections. Neonatal herpes (including neonatal encephalitis) and increased risk for acquiring and shedding human immunodeficiency virus (HIV) are the most serious consequences of genital herpes infection [8,9]. The main clinical symptoms, manifestations and complications of genital herpes infections are summarized in Table 2.

Table 2. Main clinical symptoms, manifestations and complications of genital herpes infections

Importance of laboratory diagnosis of genital herpes

Methods for laboratory diagnosis of genital herpes

The recommendations for sample transportation for testing using microscopy, culture and NAATs are presented in Table 5.

Table 5. Recommendations for sample transportation, by type of test 

The recommended sites and methods to be used for the diagnosis of genital herpes infection are presented in Table 6.

 
Table 6. Recommended sampling sites, type of sample and preferred diagnostic methods for genital herpes

Microscopy
General

Microscopic examination of lesion materials using Romanovsky staining is used by a number of laboratories in Eastern Europe [17]. This method, however, as well as cytological examination using Tzanckand Papanicolaou smears, have been found to have low sensitivity and specificity, and therefore should not be relied upon for diagnosis [5,9,18].

Antigen detection
General

Viral antigen from swab specimens can be detected using either direct immunofluorescence (DIF) or enzyme immunoassay (EIA). Commercial diagnostic tests produced in eastern European countries for the detection of herpes-specific virus antigen have not been validated against any international standard test; therefore the data presented below reflect characteristics of tests produced in western countries.

Direct immunofluorescence
DIF could be classified as a rapid diagnostic test allowing type differentiation of genital herpes viruses [19,20]. It can be valuable when testing high-prevalence populations [21], but when testing asymptomatic patients, the sensitivity may drop to less than 50% when compared with culture [19,21]. The disadvantages of DIF are that it is time consuming, labour intensive and, compared to NAATs, has a suboptimal sensitivity.

Antigen capture enzyme immunoassays
The sensitivity of commercially available EIAs, when compared with that of viral isolation, is greater than or equal to 95% and with specificities ranging from 62% to 100% for symptomatic patients [22-27]. The sensitivity of antigen capture EIAs may be higher than that of virus culture for typical presentations, but lower for cervical and urethral swabs [22-24,27]. Most commercially available assays, however, do not differentiate between serotypes.

Viral isolation in cell culture
General
Virus isolation in cell culture has been the cornerstone of HSV diagnosis over the past two decades in laboratories of western Europe [28,29] and the United States [30]. Although HSV can be isolated from over 90% of vesicular or pustular lesions, the isolation rate from ulcerative lesions is only 70% and falls to 27% at the crusting stage [4]. Delayed transport of samples to the laboratory and lack of refrigeration during transportation substantially affect the outcome of the testing [31]. The characteristic cytopathic effect of HSV in tissue culture generally appears within 24–72 hours, but may take up to five days.

Virus isolation in tissue culture roller tubes is slow and labour intensive, but has the advantage of demonstrating active infection within a clinical lesion and also allows virus typing and antiviral sensitivity testing [32]. More rapid culture of HSV can be achieved by using shell vials [33] or multiwell plates [34] and centrifuging the specimen onto cell monolayers on coverslips. Commonly used cells include primary human fibroblasts and cell lines such as MRC-5, Vero cells, baby hamster kidney and rabbit kidney cells [35,36].

Typing of HSV using cell culture can be performed directly on infected cell cultures using fluorescein isothiocyanate (FITC)- or immunoperoxidase-labelled type-specific monoclonal antibodies by DIF or by testing the cell supernatant by nucleic acid amplification tests (NAATs), with specifically designed primers.

Storage of HSV isolates
Isolates of HSV may be stored in 0.2 M sucrose in 0.02 M phosphate-buffered saline pH 7.2 (2SP medium) at –70 °С or in liquid nitrogen.

Nucleic acid amplification tests
General

As in western Europe and the United States, there are no comprehensively validated and approved commercial NAATs available for detection of HSV in many eastern European countries. However, some NAATs for HSV detection have been developed and are available in eastern Europe, but have not been validated against their internationally acknowledged analogues.

Quality control

Certified and registered reference panels comprising coded control specimens should ideally be used for intra- and inter-laboratory quality control. The use of specimen panels is standard for test system operation. These act as indicators of sensitivity, specificity and reproducibility, which are independent of the test systems used.

Serological tests

Validation of diagnostic tests

Summary

Older, classical tests can display cross-reactivity between HSV-1 and HSV-2 and even with varicella-zoster virus. During the past 20 years, a number of type-specific tests have been developed, the sensitivity and specificity of which have been evaluated to be approximately 97% and 98%, respectively [46]. Although the benefits of the serological assays (such as type-specific EISAs) include the possibility of automation and therefore simultaneous processing of a large number of samples at relatively low cost, they have a number of disadvantages that considerably limit their use in the diagnosis of genital herpes. Although the detection of HSV-specific IgM is theoretically useful to detect recent herpes infection in the absence of an IgG response, approximately a third of patients with recurrent genital herpes caused by HSV-2 have IgM responses; thus detection of IgM is a poor indicator of recent infection. Unfortunately, serological tests alone cannot inform the aetiology of a presenting genital lesion with any degree of certainty.

Recommendations

Where viral culture facilities exist, they should be maintained in order to detect the causative virus directly from skin and mucous membrane lesions. Where culture is not available, consideration should be given to the introduction of a NAAT for HSV. If NAATs are not available, antigen detection, namely DIF or EIA, could be employed, if high performance of those tests can be assured. HSV type determination is important to inform counselling and prognosis. Type-specific serology should be used for detecting asymptomatic individuals, testing pregnant women at risk of acquiring HSV infection close to delivery, men who have sex with men, and people who are HIV positive. Widespread screening for HSV antibodies should be discouraged. It is recommended that any non-validated diagnostic tests should be validated against a recommended, approved gold standard test.

Members of the Eastern European Network for Sexual and Reproductive Health Network

Acknowledgements
These guidelines were written on behalf of the STI Diagnostic Group of the EE SRH Network, which is supported by grants from the East Europe Committee of the Swedish Health Care Community, Swedish International Development Cooperation Agency (SIDA). The project coordinator is Marius Domeika.

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