Evaluation of Copan ESwab™ for the collection of Specimens for Chlamydia trachomatis, Neisseria gonorrhoeae and Herpes Simplex Virus by Molecular Methods

ABSTRACT

Introduction

ESwab™ is a FDA approved device for the collection and transport of clinical microbiology specimens. Each collection kit consists of a pre-labeled polypropylene screw-cap tube with conical shaped bottom filled with 1 mL of Liquid Amies transport medium and a specimen collection swab which has a tip flocked with soft nylon fiber. The liquid Amies transporting medium, is used as a supportive medium that can sustain the viability of a plurality of organisms that include clinically important aerobes, anaerobes and fastidious bacteria such as Neisseria gonorrhoeae during transit to the testing laboratory. In addition, to bacterial supportive medium, ESwab™ offers condition that will maintain intracellular microorganism’s viability such as Chlamydia trachomatis (CT) and intracellular virus if stored at 4°C .

The purpose of this study is to validate ESwab™ for collection and transport of specimens for Chlamydia trachomatis (CT), Neisseria gonorrhoeae (NG) and Herpes Simplex virus (HSV) testing using molecular methods.

Methods

A total of 100 specimens were used for this study; 60 specimens for CT/NG, and 40 specimens for HSV. Specimens were spiked with cell pellets collected from 1mL of previously tested positive ThinPrep® and 0.5mL of previously tested positive M4 specimens. In addition, to determine the lowest detection limits (LOD), five ESwabs™ were spiked with NG (bacterial control) ranging from 106 to 102 copies; five ESwabs™ were spiked with, CT (GenProbe® positive control containing 5fg) and HSV 1 and 2 plasmid DNA ranging from 1000 to 10 copies/reaction. For CT/NG testing, 0.9mL, 0.5mL, and 0.2mL of spiked ESwab™ specimen were then transferred to ThinPrep® transfer media (GenProbe) and run on the TIGRIS APTIMA assay. Results were compared using Relative Light Units (RLU). For HSV testing, 0.5mL and 0.2mL of the spiked ESwab™ specimen were extracted on the MagNA Pure and then tested using a real-time PCR HSV assay (Qiagen, Inc.). Crossing point (Cp) was used to compare the results.

Results

Of all tested specimens, 41 were positive for CT, 5 were positive for NG and 2 were positive for both CT and NG. The remaining 11 tests were negative and matched the results reported by the reference method. Two specimens that were discrepant, one negative and one positive for CT/NG were confirmed by repeat analysis giving the assay a sensitivity of 96% and specificity of 100%, with an overall correlation of 98.33%. Of 40 specimens tested for HSV, 25 were positive and 15 were negative, and all matched those reported by the reference method. Interestingly, there was no significant difference in RLUs or Cp between 0.9mL, 0.5mL and 0.2mL for CT/NG and between 0.5mL and 0.2mL for HSV. The results for analytical sensitivity and LOD, correlated with expected results.

Conclusions

The ESwab™ collection and transport system used for collection and transport of clinical microbiological specimens is an optimal and reliable device and meets or exceeds all required standards for collection and transport of clinical specimens for CT, NG and HSV testing by molecular methods.