Type-specific oncogenic human papillomavirus infection in high grade cervical disease in New Zealand

Background: The national Human Papillomavirus (HPV) Immunisation Programme in New Zealand was introduced in 2008, and involves routine vaccination of girls 12-13 years with a catch-up for females aged up to 19 years. The aims of this study were to measure the pre-vaccination prevalence of oncogenic HPV infection in women aged 20-69 years who were participating in the New Zealand National Cervical Screening Programme (NZ-NCSP) and who were: (1) referred with high grade cytology with a subsequent histologically-confirmed high grade cervical intraepithelial neoplasia (CIN2/3) or adenocarcinoma in situ (AIS); or (2) were in the wider group of women who had a cytological prediction of high grade squamous disease or glandular abnormality (ASC-H/HSIL+/AGC/AIS). Methods: Women aged 20-69 years appearing on the NZ-NCSP register between August 2009-February 2011 with a cytology record of ASC-H/HSIL+/AGC/AIS were invited to participate in the study. Liquid-based cytology specimens were tested for 37 HPV types using Linear Array genotyping. The prevalence of type-specific HPV infection was reported within women with histologically-confirmed CIN 2/3 and within the wider group with ASC-H/HSIL+/AGC/AIS cytology. Age-specific trends for the relative proportion of HPV 16/18 vs. other oncogenic types in CIN2/3 were assessed. Results: A total of 594 women with ASC-H/HSIL+/AGC/AIS cytology and a valid HPV test were recruited; of these 356 (60%) had confirmed CIN2/3 and 6 (1%) had confirmed AIS or glandular dysplasia. Positivity rates for any oncogenic HPV infection and for HPV16 and/or 18 within confirmed CIN2/3-AIS were 95% (95% CI: 92-97%) and 60% (54-65%) respectively; in all women with ASC-H/HSIL+/AGC/AIS cytology it was 87% (84-89%) and 53% (49-57%), respectively. The most common reported HPV types in women with CIN 2/3 were 16 (51%), 52 (19%), 31 (17%), 33 (13%) and 18 (12%). A trend for higher rates of HPV 16/18 infection compared to other oncogenic types was observed in younger women (p=0.0006). Conclusions: The prevalence of HPV 16/18 in confirmed high grade disease in New Zealand is comparable to that observed in Australia and European countries. Test positivity rates for type 52 appear higher than in comparable studies in other developed countries. A greater proportion of high grade lesions in younger women appear to be associated with HPV 16/18 infection.