Patient Registries of Acute Coronary Syndrome Assessing or Biasing the Clinical Real World Data

Background— The risk of selection bias in registries and its consequences are relatively unexplored. We sought to assess selection bias in a recent registry about acute coronary syndrome and to explore the way of conducting and reporting patient registries of acute coronary syndrome. Methods and Results— We analyzed data from patients of a national acute coronary syndrome registry undergoing an audit about the comprehensiveness of the recruitment/inclusion. Patients initially included by hospital investigators (n=3265) were compared to eligible nonincluded (missed) patients (n=1439). We assessed, for 25 exposure variables, the deviation of the in-hospital mortality relative risks calculated in the initial sample from the actual relative risks. Missed patients were of higher risk and received less recommended therapies than the included patients. In-hospital mortality was almost 3 times higher in the missed population (9.34% [95% CI, 7.84 to 10.85] versus 3.9% [95% CI, 2.89 to 4.92]). Initial relative risk...