COMPARISON OF THE MAGNA PURE EXTRACTOR TO A SWAB LYSIS METHOD FOR THE DETECTION OF HSV AND VZV IN CLINICAL SPECIMENS BY REAL-TIME PCR

Genital and dermal swabs are important sources for the detection of herpes simplex virus (HSV), and Varicella-Zoster virus (VZV) by real-time PCR. Currently these swabs are collected in M5 media, extracted by the MagNA Pure extractor (Roche Applied Science), and the extracts assayed by real-time PCR for the presence of HSV or VZV DNA. While effective for preparing specimens for testing by real-time PCR, MagNA Pure extraction adds cost, time, and complexity to the process. In this study; we compared the processing of genital and dermal swabs by the MagNA Pure system to a simple lysis method. Three-hundred specimens (176 genital, 114 dermal, and 10 ocular), and an additional 100 dermal specimens from patients suspected of having HSV or VZV infections, respectively, were processed by three different methods. A BD swab (Dacron) was placed in M5 media. Two-hundred ul were extracted by MagNA Pure and eluted into 100 ul volume. A second BD swab (Dacron) was placed into a tube containing 600 ul of neutralization buffer (NB-lab developed) without further processing. A flocked swab (Copan) was placed into a Copan MSwab tube containing 600 ul of buffer also without further processing. All three preparations were then assayed for the presence of HSV or VZV DNA by real-time PCR on a LightCycler 2.0. HSV DNA was detected in 87 of 300 specimens (29%) processed by the MagNA Pure system and in 107 of 300 specimens (36%) processed by the NB or the MSwab tubes without extraction ( p< 0.0001). In addition VZV DNA was detected in 12 of 100 specimens (12%) processed by the MagNA Pure system and in 13 (13%) or 15 (15%) of 100 specimens processed by the NB or MSwab tubes respectively. The extracts and lysed specimens were also assayed by the LC 480 instrument. The results were comparable to those obtained by the LC 2.0 for both HSV and VZV. The time to process 32 samples was longer with the MagNA Pure system (90min) than with either lysis method (10 min). Lysis of swabs for the detection of HSV and VZV DNA is faster, and provides increased sensitivity compared to specimens extracted by the MagNA Pure. The lysis technique is a faster and more practical alternative to the MagNA Pure for the detection of HSV and VZV in genital and dermal swabs.