Vaginal self-sampling for human papillomavirus (HPV) testing demonstrated a relatively low but acceptable positive predictive value in a large trial of women of low socioeconomic status in underserved areas of Mexico.
In clinic-based settings, vaginal HPV testing is at least as sensitive as cytology for detecting cervical intraepithelial neoplasia (CIN; the precursor to cervical cancer) grade 2 or worse. Vaginal self-sampling could increase screening rates, but the effectiveness of the test in home settings is unknown.
For this trial, Professor Attila T. Lorincz, PhD, of the Centre for Cancer Prevention at Queen Mary University in London, United Kingdom, and colleagues randomized 12,330 women to HPV screening and 12,731 to cervical cytology. The participants were aged 25 to 65 years.
A total of 9,202 women in the HPV screening group adhered to the protocol, as did 11,054 in the cytology group. HPV prevalence was 9.8% and abnormal cytology rate was 0.38%. HPV testing identified 117.4 women with CIN2 or worse per 10,000; cytology identified 34.4 women with CIN2 or worse per 10,000. The relative sensitivity of HPV testing was 3.4 times greater. Women with positive results from either test were referred to colposcopy. HPV testing also detected 4.2 times as many invasive cancers as did cytology (30.4 per 10,000 vs 7.2 per 10,000).
The positive predictive value of HPV testing for CIN2 or worse was 12.2% compared with 90.5% for cytology. Despite this much lower value, HPV testing of self-collected vaginal specimens may be preferred for detecting CIN2 or worse in low-resource settings where cytology screening programs are less effective. As the investigators pointed out in their report for The Lancet, women in such areas will be screened only a few times in their lives, rendering the high sensitivity of an HPV screen of paramount importance.