As described in detail elsewhere(6,7,8,9), HPV testing was conducted at every visit using an MY09/MY11/HMB01 polymerase chain reaction (PCR) assay. Amplification of a 268 bp cellular β-globin DNA fragment was included in each assay as an internal control. Following amplification, the presence of HPV DNA was assessed using filters hybridized with biotinylated oligonucleotide probes for specific HPV types, as well as a general probe mixture able to detect most anogenital HPV. For this analysis, oncogenic HPV types were defined as types 16/18/31/33/35/39/45/51/52/56/58/59/66.
