In Reply I agree with Dr Opmeer that an important barrier to the conduct of high-quality RCTs nested in the EHR will be the quality of the EHR itself. I specifically noted in the Viewpoint that this would arguably be the greatest challenge.
Opmeer focuses on lack of completeness, validity, and reliability of clinical data in the EHR. Even though I share his concerns, I would point out that these same threats already compromise all clinical research.
Derek C. Angus. Electronic Health Records as Sources of Research Data—Reply. JAMA. 2016;315(2):202. doi:10.1001/jama.2015.15422