26 Feb, 12 | by Leslie Goode, Blogmaster
A recent paper (Qiao et al.) – Journal of National Cancer Institute (JNCI) 104:3 – reports the findings of a series of 5 population-based studies of self-screening for cervical cancer in rural China, involving 13,140 participants. They are particularly relevant to STI readers on account of issues they raise about the effectiveness of screening programs in low-resource settings. An editorial in the same issue of JNCI (Patrick Petignat) provides an interesting discussion of these issues.
While a seventh of the world’s cases of cervical cancer (the third most common type of cancer in women) occur in China, a high proportion of these will be in low-resource rural settings where access to healthcare is very limited, and the kind of screening (smear or pap test) conducted in developed countries is not feasible. The last few years have seen the development of a promising alternative to the smear test, which involves screening for the strains of Human Papilloma Virus (HPV) that can lead to cervical cancer (HPV DNA). So far as low-resource settings are concerned, the latter test has the notable advantage that it can be administered by patients on themselves, and need not require significant medical resources and laboratory infrastructure.
Could self-administered HPV DNA testing provide a practicable mode of screening in areas, like rural, China where trained medical practitioners are scarce? Petignat, in his JNCI editorial, helpfully distinguishes between the issue of diagnostic performance, and the wider issue of the likely efficacy of self-testing interventions outside the research setting.
The paper (Qiao et al.) addresses the first issue. Participants in the five studies were all tested with HPV DNA administered by physician and with self-administered HPV DNA, as well as with two other tests – liquid-based cytology (LBC) and visual inspection with acetic acid (VIA) (a test that has been proposed for low-resource settings). Sensitivity and specificity of self-administered HPV DNA in detecting biopsy-confirmed cervical intraepithelial neoplasia grade 2 or more severe (CIN2+) proved to be 86.2% and 80.07% respectively as against 97% and 82.7% for HPV DNA performed by physician. Sensitivity of self-administered HPV DNA at 86.2% was actually superior to sensitivity of LBC at 80.7% and VIA at 50.3%. So far so good. The real problem with HPV DNA, whether self-administered or administered by physician, proved to be its relatively low specificity of 80.7%. Without further triage, screening with HPV DNA would result in an altogether unfeasible 15.6% of women being referred for colposcopy. A combination of self-HPV with triage using LBC or VIA might offer the most feasible solution. Computer models for the impact of these combinations were developed in the course of the study, and produced levels of referral for colposcopy of 4.8% and 4.5% respectively. Given LBC requires laboratory facilities and a medical infrastructure not likely to be achievable in a low-resource context, self-HPV combined with VIA comes out as the most feasible option.
There remains, however, the issue of the likely feasibility of self-testing interventions outside the research setting. The authors comment on the willingness of participants (70% of those invited) and the almost 100% compliance of participants with instructions. This is promising. But compliance on the part of volunteer participants is one thing: likely take-up of self-testing interventions outside such a framework is quite another, and would no doubt depend on the delivery of the intervention, as well as on a range of cultural factors. The authors refer to a relatively inexpensive testing kit – care HPV. Ultimately, however, cost-effectiveness will depend on take-up. Petignat concludes with a salutary note of warning: “Self-HPV per se is only a part of a secondary prevention program, and obstacles to program participation might not only result in program failure but also be harmful for women”. In view of this, further research seems called for.
Fang-Hui Zhao, You-Lin Qiao et al., “Pooled Analysis of a Self-Sampling HPV DNA Test as a Cervical Cancer Primary Screening Method”, Journal of the National Cancer Institute, 104:3, 8th Feb., 2012
Patrick Petignat, Pierre Vassilakos, “Is It Time to Introduce HPV Self-Sampling for Primary Cervical Cancer Screening?” (Editorial) Journal of the National Cancer Institute, 104:3, 8th Feb., 2012