Thrombocytopenia and retinopathy of prematurity

BackgroundPlatelets may act as vascular endothelial growth factor scavengers, possibly limiting neovascularization in retinopathy of prematurity (ROP). The purpose of this study was to investigate the association between thrombocytopenia (platelets <150,000/μL) and the development of type 1 ROP.MethodsThis was a retrospective 1:1 matched case–control study. Cases required laser; controls developed no or stage 1 ROP and were matched for birth weight within 100 g and gestational age within 1 week. Most recent platelet count before laser (case) and matched postmenstrual age (control) were abstracted. Conditional logistic regression was used.ResultsA total of 91 cases and 91 controls were reviewed. Of the cases, 25% had thrombocytopenia; of controls, 13% (P = 0.034; odds ratio [OR] = 2.38; 95% confidence interval [CI] = 1.04-5.43). Birth weight, gestational age, postmenstrual age, and culture-proven sepsis were not confounders in multivariate analysis. The association was significant for zone 1 (n = 16; OR = 9.00; 95% CI = 1.14-71.0) but not for zone 2 (OR = 1.43; 95% CI = 0.54-3.75) cases and controls.ConclusionsThrombocytopenia was associated with type 1 ROP, primarily among infants with zone 1 ROP. This effect may result from disease location or disease timing because posterior disease occurs at an earlier postmenstrual age. Longitudinal studies are required to further examine the roles of cumulative platelet deficits, thresholds, or critical time windows in the observed association.