Home testing for HPV infection could be a valuable tool in cervical cancer prevention, both for developing countries and resource-deprived parts of high-income countries.

A randomised controlled trial shows that vaginal self-sampling for human papillomavirus (HPV) at home could detect many cases of cervical cancer or precancerous lesions that could otherwise be missed in developing countries. Self-testing could also have a role in resource-deprived parts of high-income countries.

The findings are reported in The Lancet, written by Professor Attila T Lorincz, Centre for Cancer Prevention, Wolfson Institute of Preventive Medicine, Barts and The London School of Medicine, Queen Mary University of London, UK, and Professor Eduardo Lazcano-Ponce, Centre of Investigation in Population Health, National Institute of Public Health, Morelos, Mexico, and colleagues across Mexico.

In clinic-based settings, vaginal HPV testing is at least as sensitive as cytology—sometimes known as smear testing—for detecting cervical intraepithelial neoplasia (CIN-the precursor to cervical cancer) grade 2 or worse; however, effectiveness in home settings is unknown. In this new work, the authors aimed to establish the relative sensitivity and positive predictive value for HPV screening of vaginal samples self-collected at home as compared with clinic-based cervical cytology.

The trial recruited Mexican women of low socioeconomic status aged 25–65 years. Participants came from 540 medically underserved, predominantly rural communities in Morelos, Guerrero, and the state of Mexico.

Eight community nurses who were masked to patient allocation received daily lists of the women's names and addresses, and did the assigned home visits. Women with positive results in either test were referred to colposcopy (visual inspection of the cervix using a magnifying instrument, which may include taking a biopsy sample). The primary endpoint was CIN 2 or worse, detected by colposcopy.

12330 women were randomly allocated to HPV screening and 12731 to cervical cytology; 9202 women in the HPV screening group adhered to the protocol, as did 11054 in the cervical cytology group. HPV prevalence was 9·8% and abnormal cytology rate was 0·38%. HPV testing identified 117 women with CIN 2 or worse per 10 000 compared with 34 women with CIN 2 or worse per 10 000 identified by cytology; the relative sensitivity of HPV testing was 3·4 times greater.

Similarly, HPV testing detected 4·2 times more invasive cancers than did cytology (30 per 10 000 vs 7 per 10 000). However, the positive predictive value of HPV testing for CIN 2 or worse was 12·2% (meaning only 12% of the cases referred for colposcopy through home based HPV testing were actually positive for CIN 2 or worse by histology) compared with 90% for cytology.

The authors say: "The HPV test had a relatively low but acceptable positive predictive value, and our findings indicate the need for additional study of potentially suitable methods for triage. Vaginal self-sampling for HPV testing reduces the need for cytology clinics and permits an increase in screening coverage, especially in marginalised areas, in conjunction with more sensitive detection of cervical cancers and precursor lesions."

They add: "The challenge facing such testing as a strategy for cervical cancer prevention in low-income countries is identification of the most effective triage for HPV DNA positive women because the test substantially increases the number of colposcopy referrals,

associated costs, and risks of overtreatment. With our results we aim to inform policy formulation and programme implementation in deprived rural areas of Mexico, but these findings could also be relevant elsewhere, including in developed countries with low participation rates and localised resource-poor settings."

In a linked Comment, Dr Nubia Muñoz, Colombian Cancer Institute, Bogota, Colombia, and Dr Rolando Herrero, Prevention and Implementation Group, International Agency for Research on Cancer, Lyon, France, say although the findings of Lazcano and colleagues's study largely confirm those of earlier studies, it is the first community-based randomised trial to investigate the use of HPV testing of home-based self-collected vaginal specimen.

They also state that HPV-positive women need to be triaged using either visual inspection with acetic acid (VIA), high-quality cytology, repeat HPV testing, or other biomarkers, each method having advantages and limitations. They refer to a US study that showed that primary HPV screening of home-based self-collected vaginal specimens with subsequent clinic-based cytological triage was accurate and cost effective.

They conclude: "Mexico is, to our knowledge, the first country in the world to establish primary testing with HPV and subsequent cytological triage as the national policy, having already established a large network of high technology laboratories and done several million HPV tests...The experience in Mexico shows what can be achieved when scientific judgment guides public health policy."

Source:The Lancet