[Dr Sham Mahmood]

Hi,

Thank you for the very comprehensive modules. It really helps understanding these concepts. Could you clarify more on the differences between retrospective cohort and case control studies please?

Mithilesh

[Dr Sham Mahmood]

Thank you for your question.

The best way to break this down would be to look at the similarities first. What makes the two study designs similar?

The similarity is that case-control and retrospective cohorts are dealing with medical records that already exist. So the patient data/answers already exist at the point of the study taking place.

The cohort study looks at known exposures and looks for a particular disease – so let’s say you are looking at thrombocytosis and lung cancer – you would isolate the patients with thrombocytosis and those without thrombocytosis and then look at the data to see how many had cancer at 6, 12, 24 months.

Whereas the similar study as a case-control would run as;

You identify cases and controls – so at this given time how many patients do we have with lung cancer (cases) and then match them to the control group which is a group of patients without cancer.

You then go through the notes looking for how many patients in the lung cancer group at thrombocytosis and the same for the control group.

Hope this helps.

Sham

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