Investigation of Human Papillomavirus Prevalence in Women in Eskisehir, Turkey by Pap Smear, Hybrid Capture 2 Test and Consensus Real-Time Polymerase Chain Reaction and Typing with Pyrosequencing Method

Abstract

Human papillomavirus (HPV) infections have a broad range of clinical spectrum from subclinical or asymptomatic infection to anogenital carcinoma. The detection of HPV-DNA and determination of the risk groups in cervical cancer (CC) screening is very important because CC is considered to be a preventable illness which is the third most common cancer type of women in the world. The aims of this study were to investigate the presence of HPV-DNA in women by two different molecular methods and to compare their results together with the results of cytology, in Eskisehir, Central Anatolia, Turkey. A total of 1081 women aged between 30-65 years, who applied to Eskisehir Early Diagnosis, Screening and Training of Cancer Center (KETEM) for screening were included in the study. Three separate cervical samples were collected simultaneously from the participants for cytologic examination and molecular studies. In the first step of the study, all cervical samples were investigated for the presence of HPV-DNA by Hybrid Capture 2 (HC2; Qiagen, Germany) method. In the second part of the study, consensus real-time polymerase chain reaction (RT-PCR) (Takara Bio Inc., Japan) was performed in 152 samples which included HC2 positive and randomly selected negative samples, and then the HPV genotypes were detected by using a commercial kit based on pyrosequencing method (Diatech Pharmacogenetics S.R.L, Italy). In the first part of the study, HC2 test was found positive in 3% (32/1081) of the women, while in 4.4% (47/1081) Pap smear was positive alone or with HC2 test. Five (0.5%) samples yielded positive results with both of the methods, and four of them were positive for high risk HPV types. Cytology results were negative in 19 out of 23 (23/1081, 2.1%) samples that were reported as high risk HPV by HC2 test. On the other hand, 42 (42/1081, 3.9%) samples that were positive by cytology yielded negative results by HC2 test. In the second part of the study, 32 (21.1%) of 152 selected samples were positive by HC2 test, 40 (26.3%) were positive by Pap smear, and 53 (34.9%) were positive by consensus RT-PCR. All of the 32 samples that were positive by HC2 were also positive by RT-PCR, however 21 samples that were positive by RT-PCR were negative by HC2 test. Among 40 samples that were positive (abnormal) by Pap smear, HPV-DNA was positive in nine (22.5%) by RT-PCR and in five (12.5%) by HC2 test, but HPV-DNA was not detected in 31 (77.5%) samples by both of the tests. Genotyping of the strains could be performed in 44 samples, and the most common type detected was HPV type 16 (n=15, 34.1%), followed by type 90 (n=11, 25%) and type 18 (n=4, 9.1%). In our study, the sensitivity, specificity, positive and negative predictive values of Pap smear method were estimated as 16.1%, 96%, 10.6% and 97.5%, respectively, based on the HC2 results which was approved by U.S. Food and Drug Administration (FDA). In addition, a significant degree of concordance was detected between HC2 and concensus RT-PCR methods (Cohen's kappa: 0.665). In conclusion, regarding the insufficient number of cytopathologists in our country and according to the recommendations of American Society for Colposcopy and Cervical Pathology (ASCCP) and FDA, it was once again demonstrated that, the implementation of molecular diagnostic methods in addition to the Pap smear for effective screening of CC are needed.