Knowledge from the Noise: A Regression Discontinuity Design to Inform Optimal Transfusion Thresholds for Critically Ill Patients

Taylor and Admon discuss the study by N. A. Bosch and colleagues leveraged the noise in measurement of hemoglobin to set up a "fuzzy" regression discontinuity design (RDD) that estimates the effect of transfusing pRBCs at a threshold of hemoglobin 7 g/dl by comparing outcomes in patients just above with those just below the threshold. Selecting from three large, feature-rich datasets, Bosch and colleagues identified 191,987 patients who were admitted to an ICU with at least one hemoglobin measurement on Days 2-28 of ICU admission and who did not have active bleeding or myocardial infarction (conditions that may warrant higher hemoglobin targets and that likely would have resulted in exclusion from a comparable RCT). The assumptions necessary for fuzzy RDD were met, including general balance of other patient characteristics for patients just above and just below the hemoglobin threshold.