Evidence-based guidelines strongly recommend HPV testing in primary screening to prevent cervical cancer. Many HPV test are currently available but four were FDA approved: Hybrid Capture 2 (HC2, Qiagen), Cervista (Hologic), Cobas HPV (Roche), and Aptima (Gen-Probe). These technologies, requiring laboratory expertise and sophisticated platforms, are often time consuming and demonstrated poor feasibility in routinely clinical settings. Xpert HPV assay (Cepheid) is a new, rapid, qualitative Real-time PCR assay, able to detect E6/E7 genes of 14 oncogenic HPV types. DNA extraction, amplification and target detection take place in a disposable cartridge, complete of all reagents (1). The test requires only one hour to be completed. The first goal of this retrospective study was to investigate the analytic performances of Xpert HPV test on up to 11-year-old residual liquid-based cervical samples. Then, in accordance with Meijer’s criteria (2), we assessed the accuracy of Expert HPV. Comparisons with EasyQ HPV mRNA test (Biomerieux) and HC2 test were also done.
In our institution is placed a Tissue and Cell Biobank. Here, starting from 2001, residual PreservCyt cervical specimens are archived. We retrieved 98 specimens, collected during the years 2004-2015, and related to women referred to colposcopy for abnormal cytology result. The inclusion criteria were: HC2 and RNA test results, histological diagnosis as goal standard. Xpert HPV was performed on each single sample.
Xpert HPV test showed 6% of invalid results. A weak correlation between invalid test results and age of specimens has been found (r=0.12). At CIN2+ threshold, sensitivity and specificity were 90 and 23.5%, respectively. The unique cancer case resulted as positive. Percentage of positive samples increased with the severity of histological diagnosis. Concordance with HC2 (k=0.67), and mRNA test (k=0.61) were substantial.
These preliminary data demonstrated the excellent analytic performances of Xpert HPV DNA in residual up-to 11-year old liquid-based samples. Sensitivity appears to be equivalent to those of approved HPV tests. Specificity was low, probably due to characteristics of study population. This fact would emphasize the need of adjunctive, more specific triage test. The good agreement between Expert and E6/E7 mRNA test (both including the five most oncogenic HPV types) would support the use of E6/E7 sequences to bypass false negative results subsequent to the use of target L1 sequence (high-grade lesions are usually associated with HPV integration and loss of L1 gene). Finally, Xpert HPV assay offers simplicity of execution, rapid turnaround time and suitability for clinical setting.
1. Cuzich J et al. Performance of Xpert HPV assay in women attending for cervical screening. Papillomavirus Research 2015.
2. Meijer CJ et al. Validation of high-risk HPV test for primary screening. J Clin Virol, 2009