Association between treatment for retinopathy of prematurity and blood monocyte counts.

Purpose: To investigate blood monocyte counts as a risk factor for retinopathy of prematurity (ROP) treatment.

Design: Retrospective cohort study.

Methods: Infants who underwent ROP screening at Shiga University of Medical Science Hospital between January, 2011 and July, 2021 were included in this study. Screening criteria were a gestational age (GA) < 32 weeks or birth weight (BW) < 1500 g. The week with the largest difference in monocyte counts between the infants with and without type 1 ROP determined based on the effect size. Multivariate logistic regression analysis was applied to investigate whether the monocyte counts constituted an independent risk factor for type 1 ROP. The objective variable was type 1 ROP, and the explanatory variables were GA, BW, infants' infection, and Apgar score at 1 min and monocyte counts in the week with the largest monocyte-counts difference between the with- and without type 1 ROP groups.

Results: In total, 231 infants met the inclusion criteria. The monocyte counts in the fourth week after birth (4w MONO) exhibited the largest difference between infants with and without type 1 ROP. The analysis was performed on 198 infants, excluding 33 infants without 4w MONO data. Thirty-one infants had type 1 ROP, whereas 167 infants did not. BW and 4w MONO were significantly associated with type 1 ROP (odds ratio: 0.52 and 3.9, P < .001 and 0.004, respectively).

Conclusions: The 4w MONO was an independent risk factor for type 1 ROP and may be useful in follow-up of infants with ROP.