You don't need to be signed in to read BMJ Blogs, but you can register here to receive updates about other BMJ products and services via our site.

Cases and controls

18 Dec, 16 | by Bob Phillips

F3.mediumI’ve noticed that there are a fair few phrases in the world where there actual meaning can be unclear or uncertain, or possibly interpreted differently by folk. Take “maybe later” when used by parent to child – clearly means “no” to the parent and “yes but not now” to the child. Or “brexit”.

But the world of science can’t be confused … ┬ácan it?

Just take a gander through the field of “case control” titled studies and you may find yourself upset to discover it can. Now I am fairly clear that what I mean by case/control is a design where the participants are chosen because they have developed (cases) or haven’t got (controls) the OUTCOME of interest – they died, developed neuroblastoma or had exclusion from school. The analysis then is about finding out if these groups had different levels of exposure to a proposed causative factor, such as blood transfusions, bacon, or X-factor viewing.

What is not a case control study is one where the groups are chosen for the exposure to a treatment or not. This is a comparative cohort study.

Now as is so often the case when appraising papers, it doesn’t sometimes matter what the authors have written. It’s what they did that counts – so discount their title if the design doesn’t fit it.

– Archi

 

By submitting your comment you agree to adhere to these terms and conditions
You can follow any responses to this entry through the RSS 2.0 feed.
ADC blog homeapage

ADC Online

Education, debate, and meandering thoughts on child health, using evidence and research.Visit site



Creative Comms logo

Latest from Archives of Disease in Childhood

Latest from Archives of Disease in Childhood