The establishment of a persistent infection by some of the several high-risk human papillomavirus (HR-HPV) is a necessary step in the development of cervical carcinoma [1
]. HPV infection is frequent in sexually active people, but the persistent infection develops only in a small proportion of cases. HPV persistency involves a risk of developing precancerous cervix lesions and, eventually, cervical cancer [4
]. Among the HPVs from the genus alpha (those infecting the mucosal epithelium), 10 to 15 genotypes have been qualified as HR-HPV on the basis of their association with cancer [7
]. The World Health Organization (WHO) International Agency for Research on Cancer (IARC) include, however, at present only twelve of them (HPV-16, -18, -31, -33, -45, -51, -52, -56, -58 and -59) into such consideration [7
], the types 66 and 68 being excluded from their last classifications. However, these two types were present in the widespread classifications previously published, and most commercial tests for HR-HPV detection have included both into the design [8
]. HR-HPV genotypes 16 and 18 are the most clinically relevant, since they are involved in about 70% of cases of cervical cancer [8
HPVs cannot be cultured in vitro
by conventional methods, and the wide natural variation of the humoral immune response after the infection impairs the use of HPV-specific antibody testing in diagnosis [13
]. Diagnosis of the HPV infection is, therefore, achieved by molecular testing, mainly by detection of genomic HPV DNA.
Several practice guidelines for cervical screening have proposed in the last years the use of HR-HPV detection adjunctively with cervical cytology to screen women aged 30 and older and to determine the need for referral to colposcopy of women with ASCUS (atypical squamous cells of undetermined significance) cervical cytology results [14
]. Also, the genotype specific identification of HPV-16 and HPV-18 in women with a positive HR-HPV test and negative cytological results has been recommended [16
Two HR-HPV DNA-based screening tests have the US Food and Drug Administration (FDA) approval: in April 2003, Hybrid Capture 2 (HC2) High-Risk DNA Test (Qiagen, Gaithersburg, MD, USA) and in April 2009, CervistaTM HPV HR, (Hologic, Inc, Marlborough, MA, USA). Both techniques detect concurrently 13 HPV genotypes (HPV-16, -18, -31, -33, -45, -51, -52, -56, -58, -59 and -68); CervistaTM HPV HR test further includes HPV-66. HC2 is an in vitro nucleic acid hybridization assay with signal-amplification and Cervista is based on the Invader Chemistry®, which detects specific nucleic acid sequences using two isothermal reactions simultaneously. Other commercially available tests for pooled detection of HR-HPV genotypes are Amplicor HPV test (Roche Molecular Systems, Inc, Pleasanton, CA, USA), based on PCR amplification and Care HPV Test (Qiagen) based on hybrid capture technology detecting the same 13 HPV types included in HC2 plus HPV-66.
Given the clinical relevance of HPV-16 and HPV-18, some HPV screening assays include the specific identification of these types, and are collectively referred to as HR-HPV DNA-based screening assays with concurrent or reflex HPV-16 and HPV-18 genotyping.