Type- and age-specific distribution of human papillomavirus in women attending cervical cancer screening in Finland

Abstract

Background: Large-scale data on type-specific HPV prevalences and disease burden are needed to monitor the impact of HPV vaccination and to plan for HPV-based cervical screening.

Methods: 33 043 women (aged 25-65) were screened for HPV by a Hybrid Capture 2 (HC2) in a population-based programme. HPV-positive women (n=2574) were triaged by cytology and HPV genotyped using PCR-Luminex. Type-specific prevalence of HPV infection and its correlation to findings in cytology triage and histology as well as Population Attributable Fractions for a referral to colposcopy and findings in histology were calculated.

Results: Among HC2-positive women, 61.5% had normal, 23.1% had ASC-US and 15.5% had LSIL or more severe (LSIL+) results in cytology. Out of HC2-positive samples, 57% contained the 13 Group 1/2A HPV types, which were targeted by the HC2, 15% contained Group 2B types, 8.5% Group 3 types and 30% were found to be negative in HPV genotyping. The proportion of samples positive for HPV by the HC2, but negative in HPV genotyping increased with age and decreased with increasing cytological abnormality. The most frequent types were HPV 16 (0.9% of screened women and 12.1% of the HC2-positive women), HPV 31 (0.7% and 8.9%, respectively) and HPV 52 (0.5% and 6.3%, respectively). The prevalence of Group 1/2A HPV types increased with increasing CIN grade and attributed 78.3% (95% CI 53.4-89.9) of the CIN 3+ lesions, while HPV 16 attributed 55.8% (40.0-67.5) of them.

Conclusion: The type-specific prevalence of HPV were slightly lower than the average in international meta-analyses. Genotyping for HPV 16 better identified women with CIN 3+ than cytology triage at the threshold of LSIL+. The high proportion of women that were HC2-positive but HPV-negative in genotyping suggests that HPV genotyping may be useful also for validation of results in HPV screening. The large-scale HPV genotyping data were found to be directly useful for planning further preventive efforts for cervical cancer.

Figure 1

Flowchart of the women invited for HPV screening in 2003–2005. Results of HPV screening and genotyping, cytology triage and histology at the baseline screening visit. ¹Including seven women whose cytology triage test was missing or unsatisfactory. AIS=adenocarcinoma in situ; ASC-US=atypical squamous cells of undetermined significance; CIN=cervical intraepithelial neoplasia; HC2=Hybrid Capture 2; HPV=human papillomavirus; ICC=invasive cervical cancer; LSIL+=low-grade squamous intraepithelial lesion or worse.

Figure 2

(A,B) Age-specific distribution of the human papillomavirus types in women attending cervical cancer screening in Finland in 2003–2005. HPV=human papillomavirus.