13/01/2016 12:41 GMT | Updated 13/01/2017 05:12 GMT

Nailing Hunt's Lies

Here is the soundbite which Hunt has been repeating ad nauseam: "And at the moment we have an NHS where if you have a stroke at the weekends, you're 20% more likely to die. That can't be acceptable."

Sounds quite impressive? I tweeted him to ask for evidence and got no reply so I decided to look for my own. It wasn't hard to find. I'll deal with the best and most recent example. The headline finding from this paper is that patients admitted at weekends with a stroke diagnosis have an increased seven-day mortality of 19%, apparently just as Hunt claims.

The seven-day mortality for week-end admissions is 12.9% and for week-day admissions is 11.1% and if you factor in comorbidities etc. this gives you an adjusted mortality odds ratio of 1.19. Just as Hunt says.

But let's look more closely. At some numbers buried in the text of the paper and not even given a p value, even though they are probably the most statistically significant thing in the paper: "The overall admission rate for stroke was higher on normal week days (111 per 100 000 population; 95% CI = 110-113) than on weekends (88; 86-90) and public holidays (95; 88-102)."

So the admission rate for stroke is substantially lower at week-ends. 88 versus 111 per 100,000. See those confidence intervals? They imply that the standard error of the mean is around 1. Which means that a comparison of the two means would give a t statistic of around 13, which would give a p value so tiny that most statistics software would not even be able to calculate it.

Given that there is no earthly reason for the incidence of stroke to fluctuate wildly by the day of the week, what is obviously happening is that fewer patients with stroke are getting admitted at week-ends and that the ones who are admitted then are more severe, and hence have a higher mortality.

In fact, we can go further and quantify things. We'll make a couple of assumptions. One is that the incidence of severe stroke, i.e. one with a chance of killing you, is constant for each day of the week. Unlike, say, RTAs, alcohol poisoning or whatever. The second assumption is that somebody with a severe stroke is going to present and get admitted the same day. Strokes happen suddenly, unlike say pneumonia, appendicitis, whatever.

If we accept this, then the day of admission is the same as the day the patient has their stroke. At week-ends, 88 per 100, 000 people have a stroke and get admitted to hospital, of whom 12.9% die within seven days, which is 11.4 people. On weekdays, it's 111 per 100,000 people having a stroke and coming in, of whom 11.1% die within seven days, which is 12.3. So out of 100,000 people, every week-end day 11.4 get a stroke which will kill them in seven days compared with 12.3 for every week-day.

So Hunt is lying. If you have a stroke at the week-end you're not 20% more likely to die. In fact, according to the best evidence, you're less likely to die. Out of people admitted to hospital more die, but that can only reflect their increased severity.

The main point about all this is not just that he is misleading people on this particular issue. It is that this is the best he can come up with. The DoH is packed with people smarter than us whose only job is to find stuff to support the minister. If this is the best they can come up with it doesn't reflect their incompetence. It means that there really is no evidence at all for a "week-end effect". It means there is no problem that needs fixing. It means that Hunt is deliberately picking a fight with the medical profession over a complete non-issue, presumably to further his own political ends.

This blog first appeared on Dave's personal blog, and can be read here