The 2015 National Academies of Science, Engineering, and Medicine (NASEM) report Improving Diagnosis in Healthcare defined diagnostic error as “the failure to (a) establish an accurate and timely explanation of the patient's health problem(s) or (b) communicate that explanation to the patient.” This review and interviews with subject matter experts explored how the NASEM definition of diagnostic error has been operationalized in the literature. Of the sixteen included studies, only five operationalized the definition and only three studied communicating with the patient. The authors recommend formulating a set of common approaches to operationalize each of the three components of the NASEM definition. Patients and family should be included in defining the construct of “communication to the patient.”