Poster Presentation Australian Society for Microbiology Annual Scientific Meeting 2017

Validation of samples diluted in PreservCyt for testing for C trachomatis with the Cepheid Xpert CTNG test (#221)

David Hawkes 1 2 , Michael Malley 2 3 , Ellen Ip 2 , Marco HT Keung 2 , Marion Saville 2 4
  1. Pharmacology and Therapuetics, University of Melbourne, Parkville, Victoria, Australia
  2. Victorian Cytology Service Ltd, Carlton, VIC, Australia
  3. Centre for Epidemiology and Biostatistics, Melbourne School of Population Health, University of Melbourne, Parkville, Victoria, Australia
  4. Obstetrics and Gynecology, , University of Melbourne, Parkville, Victoria, Australia

Introduction:

Chlamydia trachomatis, (CT) is the most commonly reported communicable disease in Australia. While endocervical/vaginal swabs are considered the most accurate sampling method for nucleic acid testing (NAT), the introduction of the HPV-based National Cervical Screening Program will present laboratories with a high volume of samples in liquid-based cytology (LBC) media. As current national guidelines recommend that all sexually active people under 30 are screened annually for CT these LBC samples could provide a mechanism to increase screening. This study examined whether clinical samples diluted in a common LBC media, PreservCyt®/ThinPrep (Hologic), could be validated on the Xpert® CT/NG test.

Methods:

Samples were tested for CT using both the Roche cobas® 4800 CT/NG test and the Cepheid Xpert® CT/NG test at Victorian Cytology Service (VCS) Pathology. Samples tested on the cobas® 4800 were resuspended in cobas® PCR media (4.2 ml). Sample types used were either specimens collected from a gynaecological site or a FLOQSwab™ which had been used to collect urine. Samples tested on the cobas® 4800 were diluted in cobas® PCR media whilst samples tested on the Xpert® CT/NG test were diluted in PreservCyt® LBC media. Urine from the Melbourne Sexual Health Centre was used to supplement VCS Pathology samples to increase the rate of positive results in urine.

Results:

There was a high degree of concordance (kappa=0.943) that was statistically significant (p<0.0001) between the samples tested on the cobas® 4800 and Xpert® CT/NG tests.

Conclusion:

This study demonstrates that, although PreservCyt® is not an approved media for use with the Xpert® CT/NG test, samples collected in this media are able to be used effectively on this assay. The increased number of samples collected in PreservCyt® as part of the NCSP could help increase CT screening Australia wide.