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Guest Blog: Sampling bias and randomisation

20 Oct, 14 | by Bob Phillips

The blog series is expanding! No doubt soley inspired by now running the magnificent @ADC_JC, @davidking83 has taken up the challenge of exploring a critical appraisal nugget/thorn in response to an appraisal session.

You too could be part of our team – tweet @ADC_BMJ or find us on Facebook to get in touch – but for now, let’s settle back, imaging the warm smell of pastries and coffee, switch off our pagers and enter the Journal Club…

 

We were recently discussing a paper in my local journal club at Sheffield Children’s hospital,which was a double-blind randomised controlled trial (RCT) examining the effect of pulse oximetry on the admission rate of infants with mild or moderate bronchiolitis. This is a fascinating paper and well worth a read if you have not already. Essentially, it showed that in infants with mild to moderate bronchiolitis, clinicians are less likely to admit children if their oxygen saturations are artificially raised by 3%.

However, one of the points raised from the journal club was the possible effect of selection bias on the results of the trial. The authors state that the parents of a large number of eligible infants refused to take part and this may have introduced selection bias.

The question was raised as to if this made the study less valid.

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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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Naming culture

13 Oct, 14 | by Ian Wacogne

I’ve written lots here in the past about names - the issues of how we address each other, and how we permit patients and their families to address us.

During the process of writing those posts I made some changes to how I thought, which altered some of my behaviours. I wanted to share here some other thoughts that have accompanied this, and points that have been made to me.

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Why, what do you mean when you ask “Why?” ?

9 Oct, 14 | by Bob Phillips

109px-Aristoteles_Louvre

 

That’s not the right question.

Well. It might be the right question, but the answer might be right but differently wrong in all sorts of ways.

When parents ask – “Why has A got poorly with Ulcerative Colitis/sepsis?” – the answer might be

  1. Because humans are complicated things and sometimes break down
  2. Because the bacteria that invaded through his gut and started to multiply got nobbled by immune cells that released pyrogens and inflammatory cytokines are making everything get very upset and it’s an unpleasant sensation
  3. Because his genetics and microbiota came together in an unfortunate conflagration
  4. Because life is a series of challenges and delights towards an ultimate expression of human purpose in/through/after Death

Presuming which type of answer you’re being asked for may lead you off down a sticky wicket.

So – as is often repeated – make sure you know what’s being asked before you answer.

– Archi

(You may note that these four why?s are the Aristotelian ’causes’: material,formal, efficient and final. I have been asked, professionally, questions desiring each type of answer.)

Guest post: Making research really relevant

7 Oct, 14 | by Bob Phillips

Neuro-Oncology Group logoDo you know someone with a brain or spinal cord tumour? Has this condition touched your life?

Research is always going on into brain and spinal cord tumours – but is it investigating the things that matter most? The aim of the Neuro-Oncology Priority Setting Partnership (PSP) is to gather views from people most directly affected by brain and spinal cord tumours and agree on a ‘Top 10′ of research questions that need to be answered urgently. We gave all interested patients, relatives and health professionals the chance to submit their ‘unanswered questions’ earlier in the year and a representative group of stakeholders have whittled these questions down to just 44.

We now need your help to reduce the list of research questions further and get us closer to our Top 10?

Please give just a few minutes of your time to vote for the research topics you think most urgently need to be addressed at http://www.neuro-oncology.org.uk. … deadline Monday 13th October.

This ‘Top Ten’ will help guide research funding from the NIHR and other government and charity funders.

The Neuro-Oncology PSP is led by a Consultant Neurologist and guided by the James Lind Alliance. It is supported by brainstrust, The Brain Tumour Charity, Brain Tumour Research, Children with Cancer, the Cochrane Collaboration, the University of Edinburgh and NHS Lothian.

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

Top five tips from the UK’s National Paediatric Academic Trainee Weekend

29 Sep, 14 | by Bob Phillips

The UK’s National Paediatric Academic Trainee group organised a conference to talk about how to get on in academic paediatrics. Now, there are academics of very many flavours in paediatrics and child health, and it’s always great to see more folk turning to the (en)light(ened) path of never believing anything and ending every conversation “but more research is needed”.

One of their inaugural attendees, Hadeel Hassan (@Bezoonah) wrote up 5 key learning points…

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The New-Look ADC_JC has arrived

25 Sep, 14 | by Bob Phillips

Bristling with new folk, layered with many layers of intellectual finery, and repeatedly pointed at by folk around the world as an example of high-class education the ancient public school of Eton College has few similarities  with our online, twitter-based, journal club @ADC_JC.

But both began new years, recently, and the Journal Club opened examining the question “Anxious mothers causing anxious babies?

There’s a lovely storify that curates the whole event if you want to re-run with your own thoughts and add comments to the blog post, or relive the hour and revel in your fame.

But what’s the bottom line, I hear you asking? more…

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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