Of the Importance of Motherhood and Apple Pie: What Big Data Can Learn From Small Data.

Data integrity and validity are challenging topics to get published in medical journals. The clinical implications of these matters are not always intuitive to the reader, and data quality seldom makes headlines in the medical literature, unless something goes wrong, in which case-related conversations can make their way to the court rooms and the lay press.1 Yet, the cornerstone of our ability to make robust inference and sound clinical decisions is the assumption of the validity, accuracy, and representativeness of medical research data. Over the past few years, several articles in Circulation: Cardiovascular Quality and Outcomes have reminded us of the importance to formally examine such assumptions. Registries occupy a central role in the clinical research landscape by allowing to pool observational clinical data into larger data sets to enhance statistical power and to draw more robust inference. Registries afford expansive population coverage and contain abundant clinical data that enable valuable risk adjustment. Most importantly, registries are intended to reflect real-world practice. However, as participation is voluntary, the representativeness of patients in registries cannot be assumed as institutions that participate may differ from those that elect not to.2 Furthermore, the completeness of the data must be verified as illustrated by a study of the Can Rapid Risk Stratification of Unstable Angina Patients Suppress Adverse Outcomes with Early Implementation of the ACC/AHA Guidelines (CRUSADE) National Quality Improvement Initiative pertaining to patients with non–ST-segment–elevation acute coronary syndromes, where it was identified that records often lacked key clinical elements of the history and physical examination.3 Hence, the quality control of registries is critical to their value for outcomes research and clinical care. Regular audits of registries to assess their quality are thus essential to their use. In Circulation: Cardiovascular Quality and Outcomes , Ferreira et al4 reported on an …