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.