Prevalence of "unclassified" HPV genotypes among women with abnormal cytology.

Background: High risk human papillomaviruses (HPVs) have been unequivocally recognised as the necessary cause of squamous intraepithelial lesions (SIL) and invasive carcinoma of the cervix. The distribution and the role of unclassified risk HPV genotypes in cervical neoplasia has not been fully elucidated.

Methods: Liquid-based cytological samples were collected from 337 women referred for colposcopy following an abnormal cytological diagnosis. HPV DNA was detected by broad-spectrum PCR and genotypes identified by nucleotide sequencing analysis and reverse line blot (RLB).

Results: The overall frequency of HPV infection was 36.5% (35 out of 96) in samples negative for intraepithelial lesions or malignancy (NILM), 80% (181 out of 226) in low grade SIL and 93.3% (14 out of 15) in high grade SIL ( < 0.001). Thirty-five different genotypes were identified among the 230 HPV-positive cases. The Group 1 oncogenic viruses (HPV16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58 and 59) were found in 21.9, 46.5, and 86.7% of NILM, low grade SIL and high grade SIL, respectively. The Group 2A, including the probably oncogenic virus HPV68, was found in 1 and 0.8% of NILM and low grade SIL, respectively. The Group 2b possibly oncogenic HPVs (HPV34, 53, 66, 67, 70, 73, 82 and 85) were found in 4.2, 21.7 and 26.7% of NILM, low grade SIL and high grade SIL, respectively. The unclassified viruses (HPV12, 42, 54, 55, 61, 62, 81, 83, 84, 89, 90, 91) were detected in 8.3 and 14.6% of NILM and low grade SIL, respectively, and never in high grade SIL.

Conclusions: Group 1 HPVs were mainly prevalent in high grade SIL and low grade SIL while Group 2B were equally distributed among the two groups. The dominant frequency of unclassified HPVs in low grade SIL and NILM and their rarity in high grade SIL suggests their marginal role in cervical neoplasia of the studied population.