Human papillomavirus type specific risk of progression and remission during long-term follow-up of equivocal and low-grade HPV-positive cervical smears.

The prevalence of clinically relevant HPV types and their specific risk for progression and regression in women with atypical squamous cells of uncertain significance (ASCUS) and low-grade squamous intraepithelial lesions (LSIL) were studied in a routine screening population. A 4-year cohort of women (n = 820) with ASCUS/LSIL and a positive HPV test in triage were followed for 6-9 years. The progression risks for CIN2+/CIN3+ were determined for single (71.2%) and multiple HPV infections (28.8%). The CIN2+ progression risk for all HPV 16, all HPV 35, single HPV 16 and single HPV 35 infections were 65.3% (95% CI: 59.6-71.0), 64.4% (95% CI: 50.4-78.4), 63.8% (95% CI: 56.2-71.4) and 73.7% (95% CI: 53.9-93.5), respectively. Based on CIN2+ progression risks four main groups were defined; the HPV 16 group, the HPV 31/33/35 group, the HPV 18/45/51/52 group and the HPV 39/56/58/59/66/68 group with progression risks of 65.3% (95% CI: 59.6-71.0), 62.1% (95% CI: 54.8-69.4), 52.6 (95% CI: 45.9-59.3) and 39.5 (95% CI: 33.0-46.0), respectively. In multivariate analyses, women in the age group 40-49 years had an increased risk of CIN2+ progression. As for CIN3+, HPV 16 had a higher progression risk than other HPV risk groups (p < 0.05). In multiple infections only HPV 16 had a significant additive CIN3+ progression risk (p < 0.05) as compared to other HPV risk groups. In summary, HPV types 16 and 35, including the HPV risk group 31/33/35, had a similar CIN2+ progression risk, but only HPV 16 had a higher risk for CIN3+ progression.