A concern of screening programs, particularly those based on HPV testing, stems from the fact that many viral targets (e.g., E6/E7 HPV mRNA, or L1, L2, E6/E7 HPV DNA, whole genome HPV DNA) may be used to detect an HPV infection. Due to this aspect of HPV testing, there is a plethora of tests available either in-house or commercial, yet only a number of them have been validated and approved for routine testing. Currently, there are 254 distinct commercial tests, and more than 425 variants of those tests have been identified
[20]. These tests can be divided into hrHPV DNA, hrHPV with partial genotyping for the main hrHPVs, full HPV DNA genotyping tests, HPV DNA type/group-specific tests, hrHPV E6/E7 mRNA tests, in situ hybridization DNA in mRNA-based HPV tests, as well as tests identifying HPV DNA targeting miscellaneous HPV types
[20]. These tests are based on the principles of Polymerase Chain Reaction (PCR) amplification coupled with sequencing, restriction fragment length polymorphism (RFLP) analysis, or hybridization assays. Additionally, other tests are based on real-time detection, transcription-mediated amplification (TMA) or nucleic-acid sequenced based amplification (NASBA)
[21]. Namely, HPV tests that are currently circulating are Xpert HPV (Cepheid), PapilloCheck (Greiner Bio-One), INNO-LiPA HPV Genotyping Extra (Innogenetics), Cobas 6800/8800 HPV Test (Roche Molecular Systems Inc., Alameda, CA, USA), and HPV-Risk Assay (Self-screen BV, Amsterdam, Netherlands); hence, proper criteria (Meijer Criteria) and validation initiatives are required to ascertain which assays are appropriate for cervical cancer screening
[20][22][23][24]. Specifically, an international expert committee in 2009 proposed criteria to denote assays suitable for cervical cancer screening
[22][24]. These criteria aim to assure that candidate hrHPV tests should have an ideal balance between clinical specificity and sensitivity for the detection of CIN2/3, consequently reducing the number of follow up tests a woman has to undergo. For these purposes, new hrHPV DNA assays are compared to the Hybrid Capture 2 (HC2) or GP5+/6+ PCR- enzyme immunoassay (EIA) tests that are used as comparator tests due to their extensive clinical validation. Furthermore, each new test should be highly reproducible and applied to a clinically relevant set of samples characterized by various degrees of CIN from a screening cohort of women within the 30–60-year age group
[22][24]. In this effort of a standardized validation, the international framework “Validation of HPV Genotyping Tests” (VALGENT) was launched in order to provide a comprehensive validation and comparison for HPV genotyping tests to be used for clinically relevant results, which is achieved through the employment of sample populations that are relevant for primary cervical cancer screening
[25]. As of July 2019, there are 15 commercial HPV assays that are either completely or partially validated to be used for cervical cancer diagnostics based on primary HPV testing
[25][26][27]. The list includes but is not limited to HC2, HPV DNA Test (Qiagen), cobas 4800 HPV Test (Roche), APTIMA HPV Assay (Hologic), and BD Onclarity HPV Assay (Becton Dickinson)
[26]. In
Table 1, a selection of HPV tests is presented that are used in primary HPV screening and triage testing, as well as tests used as comparator tests for validation purposes, indicating their technical characteristics, the category they are assigned to, their validation, and intended use
[9][20][23][28][29][30][31][32][33][34][35][36][37][38].