Singh et al. report an association between anemia, red blood cell (RBC) transfusion and necrotizing enterocolitis (NEC) in preterm infants. In this case-control study, 111 preterms infants were paired to 222 matched controls. The authors studied 28 clinical variables and created a propensity score for RBC transfusions. Univariate and multivariate analyses were used. Both anemia (hematocrit
There are important limitations to this study. For example, the matching process and the method used to construct the propensity score are not well described. In spite of this, the data strongly suggest that anemia, RBC transfusion, or both can result in NEC. However, an observational study such as this one can characterize an association, not a cause-effect relationship. In other words, both anemia and RBC transfusion can be markers — not factors — of NEC. Only a randomized clinical trial can determine if anemia, RBC transfusion and/or both of them cause NEC.

– Jacques Lacroix