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Public Health Screening

Breast screening, age extension and IT errors. What next

The furore of the mistake in the breast cancer screening programme continues unabated in the press.

Of course the mistake should be put right, of course there should be a review. It would be interesting if the terms of reference for the review were openly debated, especially given the controversy breast cancer screening generates.

In my view the investigation should be undertaken with a no blame culture (unless there is obvious gross misconduct perhaps). Blame cultures tend to push mistakes further underground and make rectifying them far harder.

The whole thing really underscores the critical importance of good quality QA around screening. We are inviting people who think they are healthy for a test that will determine whether they are “healthy” or not. There are downstream consequences (read about the diagnostic oddesy). This makes the ethical position and the absolute need for perfect QA different from an offer of health care for people who have symptoms.

But lives might be saved

Of course people will be concerned that it was their mum or their aunty that was directly affected. On this it is worth reading some of the blogs and commentary published in recent weeks.

For example the SMC expert reaction, the blogs by Prof Spiegelhalter – Out of every 4 women who missed screening and then died of breast cancer, 3 would have died of their cancer anyway, even if they had gone to screening, and this excellent thread, that includes the Harding Centre infographic on the benefits and harms of screening is well worth a look in your considerations.

There will undoubtedly be individual women whose lives have been ‘saved’ by breast cancer screening, these stories make great headlines. It is worth remembering the evidence to date does not indicate an all cause mortality benefit (ie changes cause of death but not time), that evidence is about populations not individuals. There will also be women who have been harmed by screening, we rarely count these outside of clinical trials, and we certainly rarely see media reports about it.

The numbers often quoted in the media are, of course, ‘statistical’ harms . It’s impossible to state with any degree of confidence that a specific woman died because of this error. For newspapers (or lawyers) to suggest otherwise only seems to make a bad situation even worse. It’s misleading at very best and probably worse than that (thanks Chris for that snippet)

What next.

This largely depends on the result of the AgeX study. There are three possible scenarios as I see it

1.      AgeX doesn’t change risk balance equation in screening for older women from what we know now (see from Cochrane review or Marmot 2012 review in Lancet).

Net effect is we likely harm people for little to no discernible good.

There is added harm by rote of opportunity cost of resources consumed in the catch up (that could be used for more valuable interventions). But this is far harder to quantify but its like “passive harm”, rather than active harm in those actually screened.

2.      AgeX finds that harm outweighs good re screening older women. All above in play, but harm is greater

3.      AgeX finds net benefit in screening older women (ie all cause or cause specific mortality advantage that outweighs harm from over diagnosis).

Well, I will believe it if and when I see it.

Look carefully at the stat analysis plan (cue the Stato professors there as well byond my expertise) and absolute requirement for shared decision making in this process remains.

Also issues around passive harm, described above, remain in the catch up.

Whatever way, we shouldn’t do anything till we have seen and digested AgeX, we should redouble our efforts around shared decisions and good quality risk communication in this space. It might even be time to a full reappraisal for the whole approach, as per what was recently published from France.

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