before and after study, uncontrolled before and after study, uncontrolled before-after study
In studies where health conditions are measured before and after a treatment, and there is not another treatment comparison group, it is usually difficult to attribute any differences in outcomes to the treatment, since they might have occurred without the treatment. However, before-after studies can sometimes reveal dramatic effects of treatments.
For example, people almost never have spontaneously punctured colons (the lower part of the bowel), so case series that document how many people experience a punctured colon after having colonoscopy (a diagnostic test that involves inserting a tube in the colon) can provide a reliable estimate of the effect of colonoscopy on this outcome.
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