Comparative accuracy of Pap smear and HPV screening in Ubon Ratchathani in Thailand

We evaluate the potential for using high-risk human papillomavirus (hr-HPV) testing-based screening for cervical intraepithelial neoplasia (CIN) in routine health services in Thailand; its accuracy in comparison to that of conventional cytology (CC); and the utility of HPV16/18 positive results and liquid-based cytology (LBC) triage for HPV-positive women in the detection of high-grade CIN. Women aged 30-60 years in Ubon Ratchathani province, Thailand were screened with CC and hr-HPV testing and those abnormal on either tests were referred for colposcopy and/or directed biopsies. The final diagnosis using COBAS was based on histology or colposcopy when histology was not available. Estimation of test accuracy parameters was done using latent class analysis using Bayesian models. Of the 5004 women were enrolled, 20 (0.4%) had abnormal CC and 174 (3.5%) women were HPV-positive. Among 185 women abnormal on CC or HPV-positive, 176 (95.1%) underwent colposcopy, of whom 101 (57.4%) had abnormal colposcopy findings. Ninety-seven women with abnormal and 69 with normal colposcopy had biopsies performed. All 21 women with histological CIN2 or worse had hr-HPV and none were abnormal on CC. The estimated sensitivity, specificity and positive predictive value were respectively 71.8%, 97.0% and 13.0% of HPV testing; 53%, 98.7% and 20.3% for triage of HPV-positive women with LBC; and 70.4%, 98.2% and 16.9% when test positivity was taken as HPV16/18 irrespective of LBC result or positive for hr-HPV non 16/18 types and LBC triage. Our study findings indicate poor performance of cytology screening and demonstrate the potential and utility of using HPV testing in public health services in Thailand as well as the utility of primary HPV testing and LBC triage in screening for cervical neoplasia.