Prevalence of human papillomavirus types in cervical intraepithelial lesions

Background. Since the implementation of the cervical cancer screening program in Lithuania in 2004, cervical cancer incidence rates have stabilized during a 4-year period: in 2006 and 2007, 508 and 485 new cases, respectively, were diagnosed. Human papillomavirus (HPV) infection is one of the main risk factors for cervical cancer and development of intraepithelial lesions. However, not only HPV, but also HPV type, is a very important factor for malignant transformation. Cervical intraepithelial lesions with HPV 16 and 18 more frequently progress to cancer. To date, in Lithuania, studies only on HPV prevalence and risk factors have been carried out, and less attention has been paid to the identification of HPV types. The aim of this study was to identify the most common HPV types in women with various cytological lesions.
Material and methods. A total of 246 women with various cytological lesions (atypical squamous cells of undetermined significance [ASCUS], low-grade squamous intraepithelial lesion [LSIL], and high-grade squamous intraepithelial lesion [HSIL]) were included into the study. All the women were screened for HPV infections followed by HPV typing for types 6, 11, 16, 18, 31, 33, 45, and 59. Polymerase chain reaction was used.
Results. Less than half (45.5%) of women with cytological lesions were infected with HPV. The highest prevalence of HPV was detected in women with HSILs (62.1%) and CIN2 (86.7%). HPV typing revealed that the most frequent type was HPV 16 (64.3%); HPV 18 and HPV 33 accounted for 5.4% and 4.5% of cases, respectively. Based on cytologic diagnosis, HPV 16 was more frequently found in women with HSILs than women with ASCUS (77.8% vs. 50.0%).
Conclusions. The prevalence of HPV infection in women with cytological lesions was 45.5%. The highest prevalence of HPV was detected in women with HSILs (cytologic investigation) and CIN2 (histologic investigation). HPV 16 is the most common type in women with various cervical intraepithelial lesions.