Why we still need observational studies

In a NEJM editorial titled “Why we still need randomized trials to compare effectiveness” Laura Mauri also explains why we still need observational studies.

If observational registries require randomized trials to explain their results, what is their value in comparing treatment strategies? Patients who consent to participate in the controlled framework of a randomized study are systematically different from those who do not, and unselected registries are the only way to examine the generalizability of results from randomized trials. Observational studies provide detail on how and in whom treatments are being performed and how patient selection varies between treatments, but there is no substitute for randomized trials to eliminate selection bias between treatments. The two approaches are thus complementary. Observational studies allow clinical research to represent the full breadth of treated patients and offer tremendous power — especially as data are collected and analyzed with greater rigor. However, we must also continue to give priority to randomized trials on the most salient questions regarding treatment strategy and to simplify their design and conduct to be more inclusive and efficient.

I agree, but I think there are a few other crucial points that need to be made. Purposeful randomization is impractical or unethical in many cases. For example, one cannot purposefully, ethically randomize patients to treatment in low and high spending (or quality or efficiency) health care systems. Often it is hard to recruit patients to randomized trials or keep them in the arms (treatment vs. control) to which they are assigned. Randomized trials are also much more expensive than observational studies. That’s not a reason not to do them, but it, along with ethical and practical barriers, impose constraints on how many sound randomized studies can be conducted and in what areas.

I’m all for randomized trials. It’s sensible that they are the gold standard. But one should be careful about insisting on the gold standard all the time and for everything. (And, to be clear, Mauri is not.) Sometimes silver, bronze, or tin is all that is available. When that is the case, we should avail ourselves those resources and make the best of it.


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