Prevalence of High Risk Human Papillomavirus Infection with Different Cervical Cytological Features among Women Undergoing Health Examination at the National Cancer Institute , Thailand

Cervical cancer is the second leading cancer among Thai women, the incidence rate was 16.7/100,00 (Khuhaprema, 2013). Cervical cancer screening based on the Papanicolaou (Pap) smear test has been credited with a significant reduction in the incidence of this disease. For a several decades, most of hospitals in Thailand using this method for cervical cancer screening. Today, certain types of human papillomavirus (HPV) have now conclusively been shown as a necessary cause of cervical cancer (Wallboom, 1999). In addition, epidemiologic studies have shown a strong association between high-risk HPV types and the development of high-grade cervical intraepithelial neoplasias (CIN) (Kjaer, 2002; Sclect, 2001; Woodma, 2001). Alternative technologies such as liquid based cytology or human papillomavirus (HPV) screening or vaccination have been proposed as possible means to improve prevention of cervical cancer. (IARC, 2005; 2007) According to the ASCCP (American Society for


Introduction
Cervical cancer is the second leading cancer among Thai women, the incidence rate was 16.7/100,00 (Khuhaprema, 2013).Cervical cancer screening based on the Papanicolaou (Pap) smear test has been credited with a significant reduction in the incidence of this disease.For a several decades, most of hospitals in Thailand using this method for cervical cancer screening.Today, certain types of human papillomavirus (HPV) have now conclusively been shown as a necessary cause of cervical cancer (Wallboom, 1999).In addition, epidemiologic studies have shown a strong association between high-risk HPV types and the development of high-grade cervical intraepithelial neoplasias (CIN) (Kjaer, 2002;Sclect, 2001;Woodma, 2001).Alternative technologies such as liquid based cytology or human papillomavirus (HPV) screening or vaccination have been proposed as possible means to improve prevention of cervical cancer.(IARC, 2005;2007) According to the ASCCP (American Society for  (Wright, 2002), women with ASC-US should be managed using a program of two repeated cytology tests, immediate colposcopy or HPV DNA testing for high-risk HPV types.Women with ASC-H, LSIL, HSIL and atypical glandular cells should be referred for immediate colposcopy evaluation, regardless of the result of HPV testing.Therefore, detection of HR-HPV is becoming increasingly attractive as a primary screening tool.
The aim of this study is to describes the prevalence of HPV infection and to investigate the role of HPV infection in women with normal and abnormal cervical cytology.

Materials and Methods
During May to December 2011, a total of 2897 females, with a mean age of 39.02±12.00years (range, 20-55 years), underwent cervical cancer screening for routine health check up at National Cancer Institute were recruited in the study.This study was approved by the Institution Review Board and Ethic Committee of the National Cancer Institute of Thailand.
In our gynecological outpatient clinic, cervical cancer screening were performed by the combination of HPV testing and liquid-based cytology testing.The cervical sample is taken from the patients in the usual manner, cervical smear specimen were placed in tubes with specimen transport medium.The liquid-based cytologywere obtained using Thin-prep system (Hologic, Marlborough, MA).A cytotechnician reviewed all the slides and referred any abnormal findings to a cytopathologist.The cytologic results were classified according to the Bethesda system by pathology department.Abnormal cytology were defined as ASCUS or higher grade of cell abnormalities.Women underwent colposcopy (and further biopsy to visualize suspected lesions) if abnormalities were detected in cytology or HPV infection.The pathologist read the biopsies and classified them as follows: normal; cervicitis; cervical intraepithelial neoplasia (CIN) grade 1, 2, or 3, or; invasive cervical cancer (ICC).

Results
The study population consist of 2897 women aged 20 to 55 years (mean±SD: 39.02±12.00Years).61.5% of the participants have children, 22.8% were unmarried and only 1.2%reported for smoking, these factors were not different between HPV positive or negative results (data not shown).
HPV were detected in 270 of 2897 women examined (9.3%) (Table 1 We further investigated in the group of HPV-positive with normal cytology who underwent colposcopy.The HPV prevalence in normal, CINI, CINII, CINIII and cervical cancer were 57%, 90.9%, 100%, 50% and 100%, respectively (Table 3).In addition, we compared HPV prevalence among health examination women in different cancer hospitals that use the same technique .The prevalence of HPV infection in Lopburi cancer hospital,   Ubon Rathathani cancer hospital and Udon Thani were 12.1%, 18.4% and 22.4%, respectively (Table 4).

Discussion
The overall HPV infection in this study was 9.3% which consist of 7.3% non 16,18 HR-HPV 1.6% HPV-16 and 0.4% HPV-18.Age-standardized HPV prevalence varied nearly 20 times between populations, from 1.4% in Spain to 25.6% in Nigeria (Clifford et al.,, 2005).Sukvirach et al. also reported the different of HPV prevalence in Thailand (Sukvirach et al, 2003).In low incidence area of cervical cancer in Songkhla HPV infection was found 3.8%, while in high incidence area in Lampang HPV infection was found 8.0%.Earlier studies of cervical and vulvar lesions in Thailand demonstrated HPV-16 to be most prevalent (Natphopsuk et al., 2013;Ngamkham et nal., 2013;Swangvaree et al., 2013;Siriaunkgul et al., 2014).
In addition, many studies reported the prevalence of HPV infection varied according to age group (Coupe et al., 2008, Argyri et al., 2013), however others have not identified a significant relation (Burd 2003).Our results show that the prevalence of HPV infection were similar in all age groups.
As expected, HPV positivity was greater in higher grade cytology abnormalities.The prevalence of HPV infection in normal, ASC, LSIL and HSIL was 6. 7%, 46.7%, 54.8% and 80%, respectively. In 2008, Bao et al. report that overall HPV prevalence in women with normal cervical cytology was estimated to be 14.4% in Asia in a meta-analysis of 79 studies.In the LSIL group, the prevalence ranged from 33.3% (India) to 74.6% (Korea and Japan).For the HSIL group, the prevalence ranged from 75.1% (China, Hong Kong) to 85.2% (Korea, Japan) The American Society for Colposcopy and Cervical Pathology (ASCCP) suggests that women ≥30 years old, with a negative cytopathological test but a positive high-risk (HR) human papillomavirus (HPV) test should undergo HPV 16 and HPV 18 genotyping.If this test is positive, immediate cervical pathology is required.In Thailand, we conducted the last version of the clinical practice guideline for cervical cancer screening and treatment follow this recommendation.The estimated HPV16/18 positive fraction was 40.4%, 26.7% and 3.3% in women with HSIL, LSIL and normal cytology (Bao, 2008).In our study, the prevalence of HPV16/18 infection was lower than of previous report in other countries.In HSIL, LSIL and normal cytology, 24%, 6.4% and 1.3% HPV16/18 infection were found, respectively.
Although this study presented here included a large number of women of a broad age range, it has some limitations.Our sample is representative of women presenting for health examination, our sample cannot be considered representative of the Thai women.The prevalence of HPV infection varied from 9.3% in Bangkok to 22.4% in Udon Thani, this might be related with hospital based patient accrual and high rate of women with abnormal cytology.
In conclusion, the prevalence of HPV-HR, 16 and 18 in our study were lower than other studies in Asian countries.
The results of this study provide baseline information on the HPV type distribution, which may useful for clinicians to decide who should be monitored or treated more aggressively.However, larger epidemiological studies in different regions in our country are needed in order to report the accurate prevalence of HPV infection.