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A real-time polymerase
chain reaction amplification assay is a rapid and sensitive method for the
diagnosis of genital herpes.
Polymerase chain
reaction for diagnosis of genital herpes in a genitourinary medicine
clinic.
Scoular A, Gillespie G, Carman WF.
Sexually Transmitted Infections 2002;78:21-25.
Summary:
Question
What is the performance of a real-time PCR assay compared to viral culture
for the diagnosis of HSV infection in patients presenting with clinical
lesions suggestive of genital herpes?
Design
This study describes a direct comparison of a real-time PCR assay to viral
culture of genital swab samples for the detection of HSV-1 and HSV-2 in
patients presenting with clinical lesions suggestive of genital herpes.
Participants
Two hundred thirty six patients (44% male and 56% female) with clinical
features suggestive of genital herpes who attended an inner city
genitourinary medicine clinic in Glasgow, UK, were tested.
Description of Tests and Diagnostic
Standard
Two swabs were taken from each patient and placed in a randomized order in
either standard viral transport medium or PCR lysis buffer. Standard viral
cultures were performed on MRC-5 HEL cells and Vero monkey kidney cells
that were incubated for up to 10 days. In samples considered positive for
HSV, cells were dried onto a slide and stained with monoclonal FITC-conjugated
antibodies to HSV-1 and HSV-2 (PathoDx Herpes Typing, Diagnostic Products
Corporation, Los Angeles, CA).
DNA was extracted from both swabs using
the High Pure Viral Nucleic Acid Kit (Roche Molecular Diagnostics Ltd.,
Lewes, UK). Real time PCR was carried out on DNA from both swab samples
using a LightCycler (LC32, Idaho Technologies) and primers to the
glycoprotein B gene of the HSV-1 and HSV-2 genomes (KS30 and KS31). The
HSV PCR amplicons were detected using Sybr Green 1 and melting point
analysis. The amplicons from all specimens positive by LightCycler PCR
were analyzed by restriction fragment length polymorphism after
amplification by conventional PCR.
Main Outcome Measures
The number of samples positive and negative for HSV DNA by real-time PCR
compared to viral culture were determined.
Main Results
The results of virus culture and real-time PCR are compared in the table.
All PCR-positive specimens were positive in both swab samples taken. Ten
of the 21 samples that were PCR-positive and virus culture negative (24%
of all positive tests) were from patients who had past medical histories
of culture-confirmed genital herpes. Four of 20 (19%) patients who were
PCR positive, culture negative had lesions of 10 days' duration compared
with 8 of 87 (9%) patients with concordant PCR and culture results. Use of
PCR increased sensitivity by 13.3% in specimens from vesicular lesions, by
27.4% from ulcerative lesions, and by 20% from crusting lesions.
| Comparison of virus
culture with real time PCR for 236 swab samples from patients
presenting with clinical features of genital HSC infection. |
| Culture |
Real
time PCR |
Total |
| Positive |
Negative |
| HSV-1 |
46 |
0 |
46 |
| HSV-2 |
42 |
0 |
42 |
| Negative |
21 |
127 |
148 |
| Total |
109 |
127 |
236 |
Authors' Conclusions
PCR increased the overall detection rate of
HSV in genital swab samples by 24%.
Source of funding: None given
For correspondence: Anne Scoular,
Department of Genitourinary Medicine, The Sandyford Initiative, 2
Sandyford Place, Sauchiehall St., Glasgow G3 7NB, UK. E-mail address:
anne@scoular.demon.co.uk.
expert
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