Archive for March, 2011

Risk score to stratify children with suspected serious bacterial infection: observational cohort study Arch Dis Child 2011;96:361–367

What these guys looked at is a real challenge. How do i tell if the kid in front of me has just “the snuffles” or is in the early hours of something terrifying like a pneumococcal sepsis?

They do what everyone does these days and try to come up with a prediction “rule” that you can type into your iPhone and tell you what to do with your patient.

This could be a poster child for a badly done derivation set. Or let me take that back, the derivation was well done, the variables they chose to look at where silly.

They used terms like SBI=α+β1X1+β2X2+β3X3 so they must know what they’re doing right… right?

Serious Bacterial Illness (SBI) was defined kind of weirdly. They suggested an SBI was a hosptial admission PLUS one of the following. Before getting to the following…

How can a hospital admission be neccessary in a defnition of SBI? The kids that got admitted got admitted because someone thought they were sick enough – the reasons why (which are likely many) are not recorded and as a result it becomes useless in trying to “derive” a rule.

Anyhow.

So you had to be admitted PLUS some of the usual sensible things like pneumonia or pus or something like that, but they also included CRP>120 or WCC>20. So if you got admitted to hospital with a CRP>120 you apparently had an SBI. This is qute frankly nonsense. How can you have a definiton of Serious Bacterial Illnes that needs no reference to bacteria!!! You could be counted as SBI in this study if you had Still’s disease…

Sorry for getting all high-pitched and exasperated here but this stuff is really important. No matter what you do with your logisitic regression after this, you’re not gonna be able to answer the question you started with.

They recruited 2000 kids to this study. Wow that’s lots of kids surely they’ll find lots of cool things?

Unfortunately not.

Only 74 (or 3.8%) of the kids had SBI (by their definition) and remember that their definition will tend to oversetimate the SBI.

With an event rate this low it’s hard to say anything meaningful in terms of useful identifying features. Not that that stops them doing just that.

In terms of the 74 SBI kids, most had pneumonia – that’s pretty much expected. What is a little bit odd is the low rate of UTI’s. In lots of these kiddy sepsis studies UTI is way up the list and makes up lots of their numbers (and remember UTI, even a sick kid with a UTI isn’t the same as pneumonia or meningococcal sepsis) yet here (with a generous definition) it wasn’t.

As mentioned above, they calculate sens/spec and AUC and all kinds of numbers that are “accurate” but not in the slightest bit useful.

One bit is worth a quote

Apart from tachypnoea (sensitivity 71.6%), the sensi- tivity of most clinical signs was poor.

Does this mean they think a sensitivity of 71.6% is actually good?

The come up with a “rule” and I’ll spare you the details but guess what? A sick kid looks just like you’d expect a sick kid to look like.

We could do with putting our energy into teaching ourselves how to spot a sick kid with the much derided “clinical judgement”.

This isn’t much use to us.

PS by their numbers and definitions, if i just sent home all 2000 of those kids without doing a thing i would have been right 96.2% of the time. Worth noting.

The Patient as Person – 1

To continue on Ramsey

He adapts quotes from this article (remember this was a 1970 book)

all of us in the age of enlightenment need to recognise death’s growing remoteness and unfamiliarity, the masks by which it is suppressed, the fantastic rituals by which we keep the presence of death at bay and our own presence from the dying, the inferiority assigned to the dying because it would be a human accomplishment not to do so, the ubiquity of the fear of dying that is one sure product of a secular age

Comfortably Numb

I’m reading the patient as person by Paul Ramsey, trying to get the most out of my access to TCD’s library before they kick me out in April. I found Ramsey through Hauerwas who both praised and gave some serious critique to “patient as person”.

Ramsey speaks very positively about consent. With plenty of good reasons, however i’m not sure I agree with his “canon of loyalty” and joint adventuring (borrowed from Reinhold Niebuhr) as it seems to suggest that as long as it’s consensual then people can commit all kinds of violence against themselves.

With that in mind I was listening to the wonderful Joe Lex in a talk called “who was ringer and did he lactate?” (a medical joke…) where he goes through the history of some of the big names in the history of medicine.

Most amusing was the story of Bier (of the block) and Hildebrandt who were investigating the use of cocaine in spinal anaesthesia, and indeed attempting to inject cocaine into the space surrounding the spinal cord (I’m not sure even the most inventive crack addicts are into this).

Like all good medical stories, they used each other as subjects. First Hildebrandt performed a spinal tap or lumbar puncture (LP) on Bier only to find that the syringe of cocaine didn’t fit the needle and the procedure was abandoned while their friend Luer (of Luer lock fame) came up with the appropriate adaptor.

On their second attempt Bier performed the LP on Hildebrandt with success and attained profound anaesthesia of the lower limbs. Note that Hildebrandt was fully conscious, just couldn’t move or feel his legs

Let me quote

After 7 minutes: Needle pricks in the thigh were felt as pressure; tickling of the soles of the feet was hardly felt

He followed this by sticking needles into the thigh till he hit the femur and then stubbing out cigars on his legs and recording the heat but not pain felt by his friend.

Pulling out pubic hairs was felt in the form of elevation of a skinfold; pulling of chest hair above the nipples caused vivid pain

And to quote a New Scientist article on the experiment

He smashed a heavy iron hammer into Hildebrandt’s shin bone and then, when that failed to have any effect, gave his testicles a sharp tug. In a final burst of enthusiasm, Bier stabbed the thigh right to the bone, squashed hard on a testicle and, for good measure, rained blows on Hildebrandt’s shin with his knuckles.

Following the LP Hildebrandt developed the well-known post-LP headache and had to take the day off work, he never mentioned how sore his legs were, never mind any other unmentionables.

Eric the gardener

When i lived up north it was in a wee terrace house (the house i rented not the one i grew up in) with tarmac out front and concrete out back.

There was a lovely shrub/ bush thing that grew over the wall from the estate of semis behind us. It would flower come summer and look lovely.

The back yard was a good spot for bbqs but that was about it. No where to grow anything

When I moved here we moved to another terrace house but this time with a narrow but fairly lengthy strip of grass out the back. And oh the trees, sweet trees and bird song.

(incidentally, mitchelinman’s daughters set me right on the difference between a crow a raven a jackdaw and a blackbird so I have a better idea which is which now.)

We moved in in the summer and managed to get (rather overpriced) some herbs in a pot from m&s to grow. The rocket lasted till the first November snows anyhow.

Inspired by an old neighbour (as in prior not aged) and canalways I’ve gone for a bit more this year.

Part hobby and part cost saving.

It’s good being outside. Or maybe I’ll make a less morally weighty statement and say I like being outside. Having a garden gives me a good excuse.

I’d kill for an outside tap. Running the hose from the kitchen tap has it’s problems.

On the cost saving – the big one is salad. I have a diet largely consiting of beer, rocket, chorizo and tomatoes. The beer i plan to make if I can steal my brother’s beer brewing kit. The chorizo and the tomatoes are fairly cheap (you can get cherry tomatoes in tesco for 5 euro a kg if you look hard enough) but the rocket is a bit extortionate to buy. 70g for 2.50 or something like that. You could get cocaine cheaper per kg (warning vastly exaggurated estimate with no basis in reality…)

Rocket grows pretty easily. You plant some seeds and then it grows, and then it keeps growing.

I have high hopes

In addition (cause I got a bit carried away when I was buying seeds) I’ve also planted some spinach, tomatoes, broad beans, onions, basil, parsely, rosemary, and coriander. In addition to the mint and aloe vera that we couldn’t quite kill off when we first moved in.

Will have photos when the time comes. I know you’re all quivering with anticipation…

Mark Twain – A Life

I’ve been reading a biography of mark twain. The writer of huckleberry finn and tom sawyer and the innocents abroad.

He had Ginger hair (as did Churchill apparently) and  i find myself repeatedly surprised by such facts, feeling that black and white photography as somehow been telling me lies.

Twain was his pen name and he was known to everyone as Sam Clemens. He was no doubt a literary genius but he could also easily be described as an asshole. Plenty of talent too but still an asshole.

 

 

The Birds

All winter I see the birds, circling the tower in St. Patricks, roosting in the trees in the back garden. But it seems they lose their voice over winter and it’s only now with the first glimpse of spring that they find their vocie again.

Under Control

I suppose it would seem natural for the individual to sense how much their life has changed; how much of a different person they’d become. Though not always. Perhaps the change could be obvious to the others in their life and a mystery to the individual

I certainly feel that I am profoundly changed from the person I was in the post new-zealand/dying father/pre-transfarmer days.

I feel the change but struggle to quite put my finger on it. Navel-gazing introversion and poorly done existential reflection seemed par for the course for me.

Yet no longer it seems. (he says in the quiet of the back garden with the sky darkening, over a coffee, listening to evening birdsong).

When I stop and reflect these days there seems only a state of perpetual bewilderment. The self-contented smugness seems no more.

When I was single I was, on many occasions, fairly content. To the extent that I suspect I did beleive I was the captain of my soul

These days I often feel a slight awe and wonderment at how the hell I got here and what has happened to me by my understanding of myself has been somewhat altered.

My proposal is that my life – at least the married part of my life is a little bit out of control. The presence of the other and my relationship and commitment to them is beyond me.

It seems only appropriate to be bewildered by such a thing, especially for one who is a hyper-control person by nature.

 

Too young to die

For all the poor people that I quizzed over “what high-risk means” when it comes to heart attacks and strokes…

These guys are great at this type of thing. Highly recommend the podcast if you’re interested.

PROGNOSTIC VALUE OF THE DUKE TREADMILL SCORE FOR EMERGENCY DEPARTMENT PATIENTS WITH CHEST PAIN The Journal of Emergency Medicine, Vol. 39, No. 2, pp. 135–143, 2010

This paper deserves a rant, just for the sake of its ridiculous use of numbers

Most people who come to an Emergency Dept. with chest pain do absolutely fine in the long run

A small number will be having/had a heart attack. we can usually pick up these pretty well.

Some people have chest pain but not heart attack but go on to have a big heart attack over the next few months. These are the tricky ones (and unfortunately there’s a lot of them). They look well, their tests tell us they haven’t had a heart attack but the question is are they at big risk for having one in the next few months.

We have no good test for this. No matter what people might say, we don’t.

Our gold-standard test has become the angiogram, where we use dye and x-rays to look at the lining of arteries to see if they’re narrowed. While useful, it still doesn’t tell us if someone is going to have a heart attack in 2 months.

So in this slightly grey area we have to work out what’s best to do.

There is big, big money in this for someone who can work it out. And we’re already throwing big money at it.

One of the tests that has been around for a while now is the exercise stress test (EST) where we get people to run on a treadmill while we take an ECG to see if we can induce angina. Hardly the most hi-tech but hey…

It certainly is +ve more often if the person is going to have a heart attack in the next 30 days, but it’s not good enough for us to make a decision on. If all the test gives us is enough info to guess, then maybe we’re just better guessing without the test – in other words clinical judgement.

This paper took 170 of the kind of patients we’re interested in. In the ED with chest pain and an ECG that doesn’t make a decision for us and a troponin that tells us they haven’t had a heart attack.

They all got an EST and they used the Duke scoring system to stratify them low, medium and high risk.

They followed them (not in a creepy way) for 30 days to see if they had an adverse event.

And this is where it gets a bit dubious. I care about whether the patient dies or has a heart attack in the next 30 days. And they measured that, but they also measured if people got an angiogram and 1) that’s not really an adverse event in the same sense, and 2) it’s a bit subjectve; someone has to decide to do the angio, it’s not like it just happens spontaneously as part of the natural history of the disease

So this skews all their figures. They found a 3.5% adverse event rate and guess what – it was largely made of angios. Only 2 people had an MI in the next 30 days.

Especially seeing as most of the angios occurred while the patient was in hospital not when they were rushed back in a week later

With such a low adverse event rate it makes a farce of going on to calculate sensitivity and specificity, which they do anyhow.

Even more farcical is the dreaded -ve predictive value. Very basically this is the percentage chance after the test that nothing bad will happen to the patient.

They calculate it as 99.2%.

Which is nonsense. In their cohort if you simply sent them all home without the EST the percentage chance of them not having a heart attack in the next 30 days would have been 98.8%

Beware the -ve predictive value

They conclude wonderful things about their results and suggest that the EST is useful.

Did I mention that it was sponsored by a medical diagnostics company…

 

Money won’t change you

Transfarmer tends to ask good questions. And when i shut up long enough to consider them then good stuff happens

We were talking the other night about money and class and how we should live as followers of Jesus

Transfarmer asked if we should seek poverty to the extent that we come to depend on the charity of others?

I know some people – particular missionary folk who have made conscious choices of that kind – but most of us simply give out of our plenty instead of so arranging our lives so that we have less money.

Then I was reading in this little book – Finding Peace by Jean Vanier. (where the incredible story Des hommes et des dieux is also referred to)

He told the story of a group of nuns who have spent their lives living in a tent herding goats, because this is how the Tuareg people of Niger lived. The nuns felt called to be with the Tuareg people and once that was decided then living their way of life was a no-brainer of a question.

That God has a “heart” for the poor is pretty clear and if we follow Jesus we will inevitably be led towards the poor.

If we are called to be with certain parts of our community then perhaps that should shape how we live and what we do with our money.

 


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March 2011
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