Randomized clinical trials (RCTs) are considered the “gold standard” for providing actionable evidence to guide clinical decision making. However, they cannot always address important questions. For instance, statistically significant results for low-frequency outcomes like mortality sometimes require longer follow-up times or larger studies than can be practically undertaken.
In such cases, we have a choice: we can either go without evidence or we can turn to observational studies. Such studies often can be much larger and accommodate longer follow-ups. But because participants are not explicitly randomly assigned to treatment and control groups, observational studies can produce biased results. There are, however, advances in methods that can minimize that bias and increase our confidence in findings.
Consider a recent observational study comparing 2 classes of drugs that are used to treat type 2 diabetes when initial treatment fails to control blood-sugar level. The investigators…
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