Poster Presentation Australian Society for Microbiology Annual Scientific Meeting 2016

Evaluation of the AusDiagnostics Herpes Assay for the detection of Herpes Simplex Virus and Varicella Zoster Virus in clinical samples using the AusDiagnostics High-Plex system (#228)

Zamri Ahmad 1 , Todd M Pryce 1 , Ian D Kay 1 , James Flexman 1
  1. Microbiology, PathWest Fiona Stanley Hospital, Perth, WA, Australia

In this evaluation we compare an existing in-house HSV and VZV assay (Roche MagNAPure LC/LightCycler 1.0) with the AusDiagnostics Herpes assay (Roche MagNAPure 96/High-Plex 384-well Analyser) for detection of HSV/VZV in clinical samples. The AusDiagnostics Herpes Assay (AusDx) demonstrated a significant increase in sensitivity (> 2 log10) compared to the in-house reference method with a five-fold decrease in sample input volume (0.2 mL compared to 1.0 mL). To determine the utility of each method to detect experimental mixed HSV infections, controls containing HSV-1 and HSV-2 were titrated against one another at various concentrations in a chequerboard experiment. The AusDx assay was able to detect both high and low concentrations of HSV-1 and HSV-2 (and vice-versa) for all controls tested. The reference method was unable to detect low concentrations of one target when the other target was high. Fifty clinical samples were tested in a blinded prospective manner. AusDx assay demonstrated 100% sensitivity and specificity with the reference method. Assessment of assay reproducibility (extraction and PCR) was performed using the quantitative result output from replicates of an extraction control and a DNA control containing known concentrations of HSV-1, HSV-2 and VZV. The AusDx assay demonstrated good assay reproducibility across all targets. The AusDx assay was also assessed for well-to-well contamination by alternating VZV high-positive controls with negative controls. Well-to-well contamination was not observed. The AusDx assay has a sample adequacy control (human house-keeping gene) and internal control (artificial DNA) to determine sample quality and inhibition. Inhibition was not observed in the patient samples tested, however a varying degrees of sample quality were noted. Total consumable costs (extraction and PCR) of the in-house assay were also comparable with the AusDx assay. The AusDx assay has added advantages such as less hands-on time (20min compared to 45min), automated set-up, sample adequacy control, and additional targets (Enterovirus, Adenovirus group B, C, E and Cytomegalovirus). Overall the AusDx out-performed the reference method.