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Published: 21 August 2023

It is not possible to achieve zero-error cancer screening

by Dr Alan Smith, Specialist in Public Health Medicine, National Screening Service

Cancer screening programmes are destined to succeed for the many but sadly cannot reach levels of perfection. It is an upsetting reality that not every individual within a screened population can or will benefit from screening. This is not unique to Ireland, as it is a permanent feature of all population cancer screening programmes. Even though most benefit, success is rarely spoken of or reported on.

Nobody can doubt that the 58 recommendations from the Scoping Enquiry into the CervicalCheck Screening Programme (2018) has had a positive impact on its running. And with the passage of time, published data has definitively answered the impact and effectiveness question of CervicalCheck on population health.

The programme has delivered a significant decreasing trend of 2.8 per cent per year since its inception in 2008. There are many thousands of women that have benefited as a result. Despite this, there is a narrative that continues to appear intermittently in political debate and is reported on in media, including The Irish Times, which has instilled doubt, needless upset and undermined confidence in our national programme. This is that the use of a non-Irish laboratory has produced a greater than expected number of errors in CervicalCheck. Published data has proven this to be incorrect.

Before 2008, women in Ireland faced an appalling outlook in relation to cervical cancer, a killer of predominantly young women. Ireland was 20 years behind the UK in introducing a screening programme for cervical cancer. While mortality rates were decreasing in England, Wales, Scotland and Northern Ireland, mortality rates were increasing here.

To have found ourselves so far behind the NHS and 30 years behind the Nordic countries was a health policy failure. Headlines reporting six to nine months’ waiting times for a smear test were not uncommon in Ireland at the time. We had reached a critical juncture for cervical cancer screening. The position was quite simply untenable and unacceptable to the then board of the National Cancer Screening Service (NCSS) and its executive management team.

The first contract for the provision of cytology services was awarded after a competitive tender conducted in accordance with European Union procurement guidelines. It was open to all laboratories worldwide, including those operating in Ireland. The awarding of the contract to an overseas laboratory was met with what can only be described as vitriolic opposition and criticism, some of which continues to this day with less than subtle hints at times that it was a questionable process.

This is despite the fact that the 2018 scoping inquiry into CervicalCheck found no evidence to suggest at any time the NCSS was less than fair in its evaluation of the tender submissions.

Opinions were expressed that a greater-than-expected number of errors would occur as a result of the contract award to a non-Irish laboratory. In a democratic society, opinions, debate and discussion should be welcomed but, ultimately, there can be only one fact-based truth. We now have the benefit of real data.

An independent and expert panel review of cervical screening in Ireland was undertaken by the UK Royal College of Obstetricians and Gynaecologists in 2019. They concluded the findings of their review of CervicalCheck were in line with the patterns of discordance reported in their own English audit of cervical cancer and were not, in themselves, a cause for concern.

It is an indisputable fact that irrespective of where the laboratory is – be it Ireland, the United States or elsewhere – screening will always fail some individuals for the simple reason that screening is not a diagnostic test and can only prevent approximately 70 per cent of cervical cancers. Every single laboratory in Ireland that has ever provided cytology services has been the subject of litigation. Every single one. And it is a certainty the new National Cervical Screening Laboratory will also be sued.

In July, the World Health Organisation’s report on best practices in cervical screening stated it is not possible to achieve zero-error screening in standard practice, no matter how high the quality is.

The added difficulty and the many nuances of trying to attribute errors to negligence is captured succinctly in a judgment delivered by former Supreme Court Justice Frank Clarke in May 2020 when he stated “even screening processes which operate at the very highest standards can give rise to different results by competent screeners. In addition, a retrospective review of the screening process after someone has been diagnosed may well give different results, possibly influenced by the difficulties encountered with hindsight. It is thus possible that a competent screener exercising ordinary care might give a clear result, even in circumstances where it might transpire with the benefit of hindsight that there could have been suspicious material on the slide. For these and doubtless other reasons, it is not simply a case of inferring from the fact that someone obtained a clear result but subsequently was diagnosed with the relevant disease that there was necessarily negligence on someone’s part.”

The level of litigation in screening in Ireland is unprecedented – quite extraordinary, in fact – with no equivalent anywhere else in the world. The legal framework here is simply not fit for purpose when it comes to addressing legal liability for errors in cancer screening programmes.

In its report, the WHO stated the determination of whether a screening error was serious enough to be categorised as negligent needs to consider the limitations of what population cancer screening can achieve. Undoubtedly, we have reached another critical juncture for population cancer screening in Ireland.

This article was first published in The Irish Times, 21 August 2023