Inquiries on the Validation of a Model to Reduce Retinopathy of Prematurity Testing—Reply

In Reply We thank the authors for their interest in the Postnatal Growth and Retinopathy of Prematurity (G-ROP) studies. We previously reported development of the G-ROP criteria¹ and more recently successful validation in a new cohort.² The authors’ questions pertain to prediction model development. They question parameters for assessing discriminatory performance, which are associated with potential overfitting, and choice of predictive factors, which are associated with potential underfitting.