LAUSR

Design: Retrospective cohort study using data from Swedish National Patient Registry of infants screened for retinopathy of prematurity (ROP) from 1 January 2007 to 7 August 2018. The purpose was to develop and validate an individualized, predictive model to estimate risk for treatment of sight-threatening ROP using birth characteristics. (ROP treatment was Laser surgery in most cases, antivascular endothelial growth factor antibody in some cases and a combination of both treatments in a few cases, Hellstrsom A, personal communication). Outcome: The study outcome was ROP treatment (dichotomous variable based on the International Classification of ROP and Early Treatment for Retinopathy of Prematurity (ETROP) criteria for treatment). Patients: The target population was 9135 extremely premature infants’ born 2007–2018 from the Swedish National Registry for Retinopathy of Prematurity (SWEDROP). Excluded were 1388 infants >31 weeks at birth, and 138 infants with missing data, for a total of 7609 infants. From those, two internal groups were constructed: the model development group and the validation temporal group. These groups were further subdivided by gestational age, <24 weeks and ≥24 weeks, the latter being the focus of the developmental model. Hence, the internal model development group was comprised of 6947 infants, born 2007–2017; while the internal validation temporal group contained 308 infants, born 2017–2018. Same gestation age cohorts were used for the two external geographical validation models, which included 1485 infants born in the United States from 2005 to 2010 and 329 European infants, born 2011–2017. Intervention/exposure: prematurity, born 24–30 weeks gestation. Statistical analysis: Poisson regression for time-varying data was utilized with ROP treatment as the outcome and birth characteristics as predictors. Follow-up: Twenty postnatal weeks (graphs show up to 28 postnatal weeks).