Effective Cervical screening involves a complex sequence of interactions
between women, clinical staff and systems. Even in well organised
screening programmes, achieving high population coverage is challenging.
The transition to using Human Papilloma Virus (HPV) testing as the
primary screening modality, rather than cytology, has introduced the
possibility of using a self-collected sample for the primary HPV test.
This has been shown to be a reliable method of detecting CIN2+ (Polman
et al, Lancet Oncology 2019;20(2):229-38).
Regardless of the way the sample is collected, the low specificity of a
positive HPV test means that positive results must be triaged. In all
cases where self-sampling has been integrated into a cervical screening
programme to date, this triage is by cytology on a subsequent, clinician
taken sample. Other molecular tests which can be performed on the
original sample may in the future be an alternative, but are not yet
fully evaluated.
It has generally been assumed that a self-collected sample would not be
suitable for cytology because the cervix is unlikely to be thoroughly
(if at all) sampled.
However, the authors have shown that using a well-established
self-sampling device, 95.8% samples had at least 5000 cells, the usual
threshold for adequacy for cytology. (ThinPrep LBC method). Results were
highly specific, and in fact the positive predictive value (PPV) for
high grade disease was higher on the self-collected specimens than on
the subsequent professionally taken samples (Loopik et al. BJOG 2020
xxxx).
As expected, the sensitivity of the test was lower than for a
professionally taken sample, but it still detected 29.4 % of CIN2+. In
this study, an impressive 91.9% of women returned for their reflex
cytology test. This is higher than in other studies, possibly because
the study was not focussed on women who have previously not responded to
invitation.
It is likely that a significant proportion of women needing treatment
could be reliably identified by self-sampling alone by this method.
It is worth noting that despite implementation in several organised
screening programmes, self-sampling tests for HPV have yet to achieve
regulatory approval, and the process for doing so for cytology from
self-collected samples is likely to require studies with more extended
monitoring of clinical outcomes.
Self-sampling is not yet widely implemented internationally and the
pathways can be challenging. There is a concern about how to address
loss to follow up, design of multistep pathways for management, and
potential delays in diagnosis. A pathway which could reliably prioritise
women for referral for immediate colposcopy, with a high PPV for CIN2+,
without requiring a face to face clinical interaction would be extremely
valuable. This is potentially even more topical in the post COVID-19
world where there are new challenges in risks of consultations and in
capacity of health care delivery.
No disclosures: A completed disclosure of interest form is
available to view online as supporting information.