Cases and controls

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

 

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