Posts tagged with Bad Stats


The Mystery of the Toothless Bearded Hag

Flogging toothpaste may be a dull business, but for once eyes must surely have shone brighter than teeth in the marketing department at Colgate this week. A gift of a study, published in the BMJ last Thursday, linked poor toothbrushing to heart disease. The media predictably flipped the message, with headlines certain to fix a smile on even the most jaded of Colgate lips. Auntie exhorted us to ‘Brush teeth to halt heart disease’, while the Daily Mail directed ‘Clean your teeth twice a day to keep a heart attack at bay’. The ping was at last back in the Colgate ring of confidence, for who needs advertising, when sparkling headlines (351 of them, according to google) say it all?

Left Shit

The title for this post arises because Dr No has idly been playing Shorter Titles, the I’m Sorry I haven’t A Clue game in which panellists are invited to submit film (or song) titles where a single letter omission changes the meaning – Oldfinger, The King’s Peech, Rear Widow, The Godfarter, The Tird Man, that sort of thing – but as Jack Dee would say, they don’t work in print - the original title here being Left Shift, the hypothetical statistical fancy much beloved of the medical Islingtonistas who favour alcohol minimum unit pricing. Left shift is the notion that in populations the body wags the tail: the mean determines the extremes. Applied to alcohol minimum pricing, left shift has it that if average consumption falls because of raised minimum unit prices, then so too will heavy consumption fall. Populations, according to this hypothesis, behave like a blancmange made with excess gelatine: a nudge in the middle, and the whole pud moves across.

The Collapse of the Probability Function

One of the more striking changes in medicine in recent years has been the increasing use of - and reliance on - numbers. Now, cosying up to numbers is all very well, as long as you understand them. Most doctors do not.

Most Drugs Don’t Work

Just over three years ago, when few had heard of him, Dr No wrote a post called The Collapse of the Probability Function. At its heart lies the troublesome paradox that, while we might know how a group of patients might fare, we have no way of knowing how individual patients will fare. We might know that of a hundred patients, five will die in the next ten years from a heart attack. What we don’t know is who of the hundred will be the five; and the flip side of that is, when as doctors we choose to intervene, as increasingly we do, there are ninety five souls now tangled in our medical web, with all that that entails, be it tests, treatments and general apprehension, who were never going to have a heart attack anyway, let alone die from one in the next ten years. That’s a whole lot of medical intervention without any benefit whatsoever – but what the heck – overall, we might save a handful of lives - or so the hopeful reasoning goes.

Staggering Catastrophes

As a doctor who has dabbled in epidemiology, Dr No is not unaware of the siren song of care.data. Greater minds, including epideiology’s Einstein, have frothed at the prospect of the data orgy to be had, only to have it dawn that theirs was a premature cigar. Yet even when left staggering at the catastrophes revealed, a hard core group still want care.data to happen, the idea being that if enough corks are inserted, then nothing will leak.

If only! Dr No remains persuaded that the call of care.data is indeed the song of a siren balanced on dangerous rocks. However alluring the song, the rocks remain; many rocks, but four stand out as especially dangerous.

Death Bandits

The Hospital Manager’s Association

Top Secret – Eyes Only

The Hospital Manager’s Guide to Massaging HSMRs

Members will be aggrieved to hear that the Doctor Foster Intelligence Unit and its lottery hospital standardised mortality ratios (HSMRs) are here to stay, despite several recent papers showing the methodology to be unsound.

Members will appreciate that they supply the raw data used by Dr Foster, thus providing opportunities to ‘cook’ the figures before they are passed to Dr Foster. The Association does not condone directly tampering with the data; however, faced with the intractable use of flawed statistics, the Association does believe members are entitled to ‘game’ the system to their advantage.

Nature Cooks the Books

Even at the best of times, epidemiology can seem as dry as old biscuits, and when it starts counting stiffs – as it so often does – it can smell not just dry and old, but musty too. But it is an important ology, and when done well, which is surprisingly difficult, it can tell us useful things.

This morning on Radio 4’s Today programme, we had Professor Bruce Keogh, a Department of Health chief pongo, putting the icing on an epidemiological cake he had himself helped bake. Having started soundly enough, he suddenly veered off-piste, gathered speed, and delivered a shopping list of deliverables that bore no relation to the study he and Wingnut had only a moment ago been discussing. “For me,” Prof Cough said, “the big prize …is about our NHS catching up with other service industries and offering a routine six or seven day week…where people can have routine operations over the weekend…at their convenience…access to expert advice…that’ll put the compassion back into the NHS”. Compassion? It sounded more like commerce to Dr No. It was, of course, a government inspired vision for the 24/7 hospital, where every day is Wednesday, every patient a consumer, and all the clocks strike thirteen.

The Computer Says You Have Schizophrenia!

In his zeal to declare the NHS open for business, David Cameron announced in December 2011 that it was ‘simply a waste’ not to flog off anonymised NHS data to the pharmceutical industry, to help development of new drugs and their testing on hapless patients. Dr No has presented this somewhat tongue in cheek: the NHS does have vast amounts of data, albeit of varying quality, and there is legitimate and useful research to be done on that data. Indeed, Dr No has in the past done just such research. The red rag to Dr No’s bull was the sale of data to commercial concerns. Here, on the other side of the public-private divide, the rules such as they are, are different. We are advancing on Libor country. Profit, not patients, now rule, and it is remarkable how bendy the rules can become. Recently, the life insurance industry poked a sharp stick in GPs’ eyes by using subject access requests to obtain customer (subject) medical records, shaving the best part of £100 off the cost. It may not be illegal, but it is certainly tacky.

The Blind Archer

Hell may have no fury greater than a woman scorned, but surely Heaven can have no joy greater than a woman reformed. In a remarkable development, scientists in North America have popped not a bun but a biodegradable scaffold layered with a patient’s vulval and other cells in the oven, and after the required time at the requisite temperature been rewarded with a fully formed vagina. Four women born without a vagina have had ready-vaginas made this way implanted, and have subsequently reported normal or even atomic levels of ‘desire, arousal, satisfaction and orgasm’. This extraordinary advance may in the short term pave the way for a gruesome commerce in designer vaginas – each scaffold is individually crafted - but in time it can only end one way: the day will dawn when we pop not buns but homunculi in the oven, to be rewarded nine months later with little incubi, all of whom will go on to report normal or even atomic levels of desire, arousal, satisfaction and orgasm. Truly, science knows no bounds.

Stiff Counting

There has been much ado about hospital death rates lately, much of it focused on the Mid Staffs hospitals, where consistently high apparent death rates were repeatedly brushed aside and ignored. The issue at stake was the validity - or not - of certain statistics produced by Sir Jar and his operatives at HI5, the Dr Foster Intelligence Unit, and one statistic in particular, the HSMR.

The HSMR, or Hospital Standardised Mortality Ratio to give it its full name, is said by Sir Jar to offer a useful marker of a hospital’s performance, by providing a single figure that summarises how many patients leave the hospital feet-first. High value HSMRs suggest more stiffs than expected, low HSMRs indicate less stiffs than expected, compared to national figures. Unfortunately for Sir Jar, the method – quite apart from a myriad of other factors that might compromise validity - he uses to determine HSMRs suffers from a flaw that severely restricts its application. While an isolated HMSR can be compared to the ‘big picture’ – in other words, the standard population to which it is being compared - comparisons between hospitals, or even the same hospital over time, are prone to errors, which can render the results at best meaningless, at worst misleading.