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archimedes

Why not look at what you already know?

16 Oct, 14 | by Bob Phillips

A little while ago we blogged on the surprisingly varied methods folk use to pick how how big an effect needs to be in order to be ‘clinically relevant’. A further paper on this theme has emerged that takes up a slightly different aspect of the challenge of getting the number right before doing a trial.

On the basics front, before you know how many people will be needed for a trial, you need to know

  • How big an effect you might see
  • How varied the effect is between people
  • What size of effect is gong to be ‘clinically relevant’ (ie above what level you want to prove the intervention will lie)
  • What chance of making the wrong call (“It works!” when it doesn’t, or vica versa) you are prepared to accept

It may be rather surprising to find that there hasn’t been, until very recently, a really well developed way of using systematic review / meta-analysis methodology to capture the stuff we already know before moving onwards to find out more, when moving between phase II (how-toxic-is-this-and-does-it-make-markers/images-better?) and phase III (are-there-fewer-dead-people?) trials. But now there is.

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Publication bias.

2 Oct, 14 | by Bob Phillips

SO – you all know about publication bias? The fact that nasty, authoritarian Journal Editors, sat with their cigars, expensive brandy and well-roasted coffee look upon trials that don’t give positive results and consign them to the pit of Rejection?

(That’s just how it happens.)

Well, there’s another variants on this theme.

There’s the “we’ll only write up that outcome measure ’cause it says what we want it to show” bias (aka ‘selective outcome reporting’)

And then there’s the “can’t be arsed” bias, where studies just don’t even get written up or presented as their overwhelming lack of showing anything leads their authors to torpor. I particularly hate systematic reviews of case reports for this trouble.

And it happens with normal people too. A really lovely piece of work shows that Amazon dieting reviews show massive publication bias, probably by self-selection, and that folk buy into believing them wholeheartedly. As PT Barnum said – “there’s one born every minute”.

– Archi

StatsMiniBlog: Spot on, time and again.

22 Sep, 14 | by Bob Phillips

20140205-091454.jpg

“Spot on!” is a rather anachronistic and very Anglophile phrase, redolent of croquet lawns, tweeds and well designed woven straw hats. It’s no wonder we tend to use  – if we are being technical – the word “accurate” instead.

But should we be using the word “precise” to make ourselves sound all academic? And what’s the difference?

 

Accuracy – the closeness a thing to it’s target

Precision – how close repeated attempts are to each other

Now those two things do not have to be connected – you may be accurate and imprecise, or inaccurate but very precise, or .. Oh forget it.

Let me just show you a picture …
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Routine data vs research expense

18 Sep, 14 | by Bob Phillips

Lots of debates could be had off this title. When is an ‘audit’ and audit and when is it a cloaked piece of poor quality retrospective research? Why is ‘research’ considered better just because it’s ‘special’? What makes research study data forms nearly impossible to understand without spending 3 days in a steam hut wearing just a loincloth made of old patient information leaflets and drinking far too much Red Tea?

What I think it’s worth taking up, for a just a bit though, is ” What is routinely collected hospital data and it’s relationship with the real world? ”

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A grain of sand.

15 Sep, 14 | by Bob Phillips

I am a glutton for podcasts, occasionally medical, but often way off this mark (sociology, philosophy & rugby league would fall into this category), yet they frequently play into each other. Some of you will recall this, as I note that when I can’t concentrate on a podcast, I know I’m becoming overloaded/over worried and need to step away from stuff to regain my good mental health. Podcasts are my pants drawer.

However, my own state of mind is not the key in this entry, but an ancient philosophical problem.

The Sorites Paradox.

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Top tips for detecting adverse events in paediatrics

11 Sep, 14 | by Bob Phillips

How can we determine the safety if anything we do in paediatric prescribing? For chronic conditions, we’re generally pretty sure that if we let it wind on, it will harm the child. If we treat it, we’ll be managing the disease but causing adversity. The balance is making this tip where the good stuff overwhelms the poor stuff.

I think the commonest, extreme, example is chemotherapy. These agents are intended to treat a cancer to save a life. To do this, they may cause sufficient immunosupression to produce a fatal infection, or mucosal erosions to give a fatal intestinal perforation, or a thrombotic event that produces a cerebral infarct and death. The carefully measured doses of these drugs are placed to  make the tipping point in favour of benefit over harm; and we have improved survival in childhood cancer by this treatment approach.

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Basics. Why bother with systematic reviews?

7 Sep, 14 | by Bob Phillips

If you’ve only recently bumped into this blog, you may not be aware of the near-obsessive compulsion for us to ask “Is there a systematic review of that?” at any opportunity. Why is this the case? Well, partly it’s the job. Mostly it’s because systematic reviews give us the best answers to our questions … and in this Basics blog we’ll cover

  • What is a systematic review?
  • What is meta-analysis?
  • What can a systematic review do for us?

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How can we share treatment decisions?

3 Sep, 14 | by Bob Phillips

pot_of_gold_rainbow (107x160)I guess part of me wants to start this blog with “Never knowingly topical”, but in the UK an as yet unclear explosion of media interest has been generated around decision making and a child with a brain tumour.

Those who want to can find out more via reputable news sites – as a staunch middle-class Northerner, I’ll just link to the BBC from the start of the very long story.

Where much of this very difficult story seems to be around consent, and best interests, I’d like to take a more routine approach to the issue. How do we, in everyday care, make sure that our interactions with children, young people and their families share the decisions as much as possible?

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Which O for PICO?

31 Aug, 14 | by Bob Phillips

 

We’ve mentioned before about the COMET initiative, that was born from lots of work in rheumatology, and seeks to standardise a core set of outcomes collected in clinical trials so that the trial

  1. Measures things of importance to patients, clinicians and researchers and
  2. Provides a degree of homogeneity that makes systematic reviews more powerful

Well, those clever rheumatologists have done it again, conceptualising the whole of it into two major areas, and breaking them up into manageable parts.

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A picture paints a thousand words

20 Aug, 14 | by Bob Phillips

 

Pretty much sure that you’ve all hit something complicated and, after trying to explain it, have grabbed pencil, paper and said something like “Look, you see, it’s …”

 

And your picture may be completely unlike the thing you’re describing.

 

Well, hot on the tails of our Archi blog about the challenges with ‘standard care’ as a comparator comes a really nice way of thinking about complex variations in studies included in systematic reviews. Admittedly, the title is a tad off putting “Evidence-based mapping of design heterogeneity prior to meta-analysis: a systematic review and evidence synthesis” but the idea – along with it’s beautiful execution in examples – is that we can use a rather neat tabular design to outline where studies vary and how this might explain differences and need to be understood in our translation / incorporation of the outputs into clinical practice.

 

There’s a wealth of stuff written about visual display, and of course, an entire industry dedicated to it, but we docs do tend to ignore all that sort of stuff, don’t we?

What’s your ‘best’ example of great graphical representation making something terribly complicated enlightened? Comment, FB us, or tweet it to @ADC_BMJ #NowIsee

 

 

 

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