Early Haemoglobin Oxygen Affinity as a Hypothesis‐Generating Marker for Retinopathy of Prematurity Risk in Preterm Infants

Purpose To investigate whether postnatal haemoglobin oxygen affinity (P 50 ), derived from serial arterial blood gases, is associated with the risk of retinopathy of prematurity (ROP) in preterm infants, as a potential physiologic marker. Study Design Retrospective cohort study. Methods This study included 232 preterm infants born < 32 weeks gestation. Haemoglobin P 50 and lactate values were calculated daily during the first week of life. The primary outcome was the development of any ROP; treatment‐requiring (Type 1) ROP was a secondary endpoint. Associations were analysed using logistic regression and ROC analysis. Results Infants who developed ROP had significantly higher Day 7 P 50 values (mean 26.9 ± 1.8 mmHg) than those without ROP (26.1 ± 1.7 mmHg; p = 0.003). A Day 7 P 50 > 26.4 mmHg was independently associated with ROP (OR 2.5; 95% CI 1.3–4.9), though predictive performance was modest (AUC 0.60). Lactate levels showed no association with ROP. P 50 was not predictive of Type 1 ROP. Conclusion Increased postnatal P 50 may be modestly associated with ROP development, reflecting impaired oxygen delivery during early retinal vascularization. While not suitable for screening, P 50 may serve as a physiologic marker warranting further mechanistic investigation.