The Xpert HPV test (Cepheid) detects HR-HPV 16, 18-45 and 3 groups of other HPV types (P3 : 31-33-35-52-58, P4 : 51-59 and P5 : 39-56-66-68) by PCR, including the detection of a reference gene, confirming an adequate cellularity. To date this technique hasn’t yet been evaluated for cervical smears fixed in BD-SurePath transport medium.
The HC2 (Qiagen) HPV test targets 13 HR-HPV types (no HPV 66 detection).
The aim of the study was to evaluate the performance of the Xpert HPV test on SurePath fixed cervical smears by comparing it to the HC2 HPV test as reference method.
We tested 110 consecutive SurePath ASCUS smears by HC2 and Xpert HPV using the residual cell pellets after BD-autocyte® PAP cytology.
Samples with discordant results were submitted for detailed genotyping by Inno-LIPA PCR Version Extra II (Fujirebio).
We further evaluated the repeatability (5x) with different technicians on 2 different modules(4 HPV+ and 1 HPV- smears), the stability across time of one positive smear at 1, 7, 14 and 28 days and the reproducibility between the initial vial and the residual cell pellet (35 samples).
Of the 110 HC2 tested ASCUS smears, 57 were HC2 HR-HPV+, 53 were HC2 HR-HPV-. The overall concordance was 89.1%, the negative concordance was 96.2% (two HC2- smears were Xpert HPV+) and the positive concordance was 82.5% (of 57 HC2+ samples, 10 were Xpert HPV-).
Among these 10 HC2+/Xpert HPV- smears genotyping revealed : one HPV 39+, one HPV 52/66/70+, one HPV 33/53+, one HPV 33/35/51/58/53/70/52/44+ and six not targeted HPV types : four HPV53+ samples, two of them coexpressing HPV54 or HPV67, one HPV67+ and one not yet classified HPV type.
Among the HC2-/Xpert HPV+ cases one was HPV 18/66/70/62+ and one HPV 16/51/62+.
The repeatability according to different technicians/modules and across time was 100%. The reproducibility between initial vials and cell pellets was 97%.
When we look at the 10 HC2+/HPV- cases and considering the targeted HPVs, after genotyping only 4 Xpert HPV- cases were true false negatives, all of them with a RLU/cut off ratio < 5 considered at low risk for CIN2+(1). None was false positive.
The other 6 HC2+/Xpert HPV- concerned non targeted HPVs due to cross-reactions of HC2 with low risk and potentially HR-HPVs. Colposcopy was normal for 5 of these 6 patients, 2 of them with a biopsy within normal limits.
Two HC2-/Xpert HPV+ smears were probably related to insufficient sample quantity.
Our global, negative and positive concordances (89.1%, 96.2% and 82.5%) show a performance quite similar to the ones reported for the PreservCyt (Hologic)(2,3).
The SurePath transport medium is suitable for routine HPV testing with the Xpert HPV.
1. Jarboe et al. A weakly positive HPV HC2 result correlates with a significantly lower risk of CIN2,3 after ASCUS cytology, J of Lower Genital Tract Disease, 14(3):174-8, 2010.
2. Rabaan et al. Comparison of Xpert HPV and HC2 DNA Test for detection of high-risk HPV infection in cervical ASCUS, J Infect Public Health 10(2):219-223, 2017.
3. Castle et al. Reliability of the Xpert HPV assay to detect HR-HPV DNA in a colposcopy referral population, Am J Clin Pathol, 143(1):126-33, 2015.