Real time PCR diagnosis of genital herpes in routine practice
Genital herpes is the fourth most common sexually transmitted disease in the UK with over 18 000 new cases reported from genitourinary medicine clinics in 2002. Clinical diagnosis is neither sensitive nor specific and virus isolation is slow and decreasingly sensitive as the lesions age. Polymerase chain reaction (PCR) increases herpes simplex virus (HSV) detection rates and newer real time PCR assays are fast, safe, and fully automated. Simultaneous detection and typing of HSV can be performed using software analysis of the probe melting temperature (Tm) values of HSV-1 and HSV-2 specific probes. Now data from a London, UK, sexual health clinic have shown the feasibility and value of real time PCR diagnosis of genital herpes in routine clinical practice.
Genital swabs from 233 consecutive patients with suspected genital herpes were tested by virus culture and automated real time PCR. HSV was detected in 79 samples (34%) by culture and 132 (57%) by PCR. Detection rates (culture v PCR) in the first 145 patients were 31% v 49% for first episodes, 31% v 58% for recurrent episodes, 42% v 59% for early (<5 days) lesions, 22% v 48% for later lesions, 34% v 64% for ulcerated lesions, and 25% v 31% for non-ulcerated lesions. They were 28% v 51% in men and 35% v 57% in women. In HIV positive patients the detection rates were 41% v 71% and in HIV negative patients 34% v 55%. Overall detection rates in this first part of the study were 31% v 53%. In the subsequent 88 patients detection rates were 39% v 63%. In the whole cohort 91% of HSV positive samples were typed as HSV-2. PCR results (detection and typing) were available in less than four hours and the results were highly reproducible. In a comparison of three specimen preparation methods (manual DNA extraction with the QIAamp DNA mini kit, automated DNA extraction with MagNA Pure LC, and virus precipitation with PEG) PEG precipitation was the most sensitive, quickest, and cheapest.
Real time PCR is labour efficient, and feasible in routine diagnostic settings. It provides accurate and rapid results for the detection and typing of genital HSV infection.
