Performance of a cartridge based assay for the detection of clinically significant HPV infection - lessons from VALGENT (Validation of HPV Genotyping Tests)

The Validation of Genotyping Tests-HPV (VALGENT) studies offer an opportunity to clinically validate HPV assays for use in primary screening for cervical cancer and also provide a framework for the comparison of analytical and type-specific performance. Through VALGENT, we assessed the performance of the cartridge-based Xpert HPV Assay which detects 14 high-risk (HR) types and resolves HPV 16 and HPV 18/45.

Samples from women attending the UK cervical screening programme enriched with cytologically abnormal samples were collated. All had been previously tested by a clinically validated standard comparator test (SCT) – the GP5+6 EIA. Clinical sensitivity and specificity of the Xpert HPV for the detection of CIN2+ and CIN3+ relative to the SCT were assessed as was inter and intra lab reproducibility according to international criteria for test validation (1). Type concordance for HPV 16 and HPV 18/45 between the Xpert and the SCT was also analysed.

Xpert HPV detected 94% of CIN2+ and 98% of CIN3+ lesions among all screened women and 90% of CIN2+ and 96% of CIN3+ in women of 30 years and older. The specificity for ≤CIN1 was 83% (95% CI 80-85%) in all women and 88% (95% CI 86-91%) in women 30 years and older. Inter and intra laboratory agreement for the Xpert was 98% and 97% respectively. The kappa agreement for HPV16 and HPV 18/45 between the CVRT (GP5+/6+ LMNX) and the Xpert was 0.92 and 0.91 respectively.

The clinical performance and reproducibility of Xpert is comparable to well established HPV assays and fulfils the criteria for use in primary cervical cancer screening.