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Age-specific prevalence of human papillomavirus by grade of cervical cytology in Tibetan women.

BACKGROUND
Human papillomavirus (HPV) is believed to be the most common sexually transmitted infection. However, little is known about the prevalence and distribution of HPV types in China. We aimed to assess the prevalence and the distribution of HPV types as well as risks for abnormal cervical cytology in women who reside in the Tibetan Autonomous Region of China.


METHODS
A cross-sectional study was performed involving a sample of 3036 women. An epidemiological questionnaire was applied and cervical specimens were obtained for liquid-based cytology and HPV DNA detection. Statistical analysis included chi-square and Logistic regression model.


RESULTS
In this population, 3.66% (111/3036) had atypical squamous cells of undetermined significance (ASCUS), 1.45% (44/3036) low-grade squamous intraepithelial lesions (LSIL) and 1.09% (33/3036) had high-grade squamous intraepithelial lesions (HSIL). Tibetan women (5.74%, 137/2387) exhibited lower abnormal cytology rates than non-Tibetan women (8.01%, 52/649, P = 0.03). The overall prevalence of HPV infection was 9.19% (279/3036). We failed to identify any differences in HPV prevalence by age. In the groups with normal, ASCUS, LSIL and HSIL, the overall HPV prevalences were 7.41% (211/2847), 24.32% (27/111), 56.82% (25/44) and 45.45% (15/33), respectively. HPV 16 (1.52%, 46/3036) was the most common type, and was also the most prevalent in women with ASCUS (8.11%, 9/111) and HSIL (15.15%, 5/33). The most common HPV type for Tibetan women was HPV 16 (1.42%, 34/2387), whereas for non-Tibetan individuals it was HPV 33 (2.31%, 15/649). Of the 279 HPV-infected women, 40 individuals (14.34%) presented with multiple HPV positivity. Women who had two pregnancies were more likely to have abnormal cytology smear (OR = 1.67; 95%CI: 1.07 - 2.61).


CONCLUSIONS
A low prevalence of HPV positivity was observed in women who reside in the Tibetan Autonomous Region of China. The prevalence of abnormal cervical cytology and HPV type distributions were different between Tibetan and non-Tibetan women.