The relationship between hemoglobin and the predicted probability of being underweight (WAZ < −1) with 95% CIs from a logistic regression model of the combined cohort (n = 2000) of children with SCA screened for the SPRING and SIT trials. This is a graphical representation of the interaction term between the hemoglobin level and cohort in the model. Underweight (WAZ < −1.0) was defined using z scores calculated from the World Health Organization growth reference and Canadian Pediatric Endocrine Group growth charts.