Development and comparison of a rapid isothermal nucleic acid amplification test for typing of herpes simplex virus types 1 and 2 on a portable fluorescence detector.

We have developed a rapid and simple molecular test, the IsoGlow HSV Typing assay, for the detection and typing of herpes simplex virus (type 1 and 2) from genital or oral lesions. Clinical samples suspended in viral transport mediums are simply diluted and then added to a helicase-dependent amplification master mix. The amplification and detection were performed on a portable fluorescence detector called the FireFly instrument. Detection of amplification products is based on end-point analysis using cycling probe technology. An internal control nucleic acid was included in the amplification master mix to monitor the presence of amplification inhibitors in the samples. Because the device has only two fluorescence detection channels, two strategies were developed and compared to detect the internal control template: internal control detected by melting curve analysis using a dual-labeled probe, versus internal control detection using end-point fluorescence release by a CPT probe at a lower temperature. Both have a total turnaround time of about 1 hour. Clinical performance relative to herpes viral culture was evaluated using 176 clinical specimens. Both formats of the IsoGlow HSV typing assay had sensitivities comparable to that of the Food and Drug Administration-cleared IsoAmp HSV (BioHelix Corp., Beverly MA) test and specificity for the two types of HSV comparable to that of ELVIS HSV (Diagnostic Hybrids, Athens, OH).