Infants' characteristics at birth, first sign of ROP and ROP treatment
| Model development group (N=6991) | Validation groups (N=1241) | P value* | |
| Girls | 3158 (45.2%) | 607 (48.9%) | 0.016 |
| GA at birth (weeks) | 28.3 (1.9) 28.6 (24.0; 30.9) | 28.0 (1.9) 28.3 (24.0; 30.9) | <0.0001 |
| GA (full weeks) | 0.0007 | ||
| 24 | 427 (6.1%) | 94 (7.6%) | |
| 25 | 597 (8.5%) | 114 (9.2%) | |
| 26 | 781 (11.2%) | 129 (10.4%) | |
| 27 | 914 (13.1%) | 187 (15.1%) | |
| 28 | 1141 (16.3%) | 239 (19.3%) | |
| 29 | 1419 (20.3%) | 236 (19.0%) | |
| 30 | 1712 (24.5%) | 242 (19.5%) | |
| Birth weight (grams) | 1146 (339) 1135 (307; 3245) | 1068 (319) 1065 (335; 2450) | <0.0001 |
| Birth weight SDS (Niklasson and Albertsson-Wikland 2008) | −1.03 (1.37) −0.77 (−8.56; 4.93) | −1.31 (1.57) −0.99 (−9.92; 2.75) | <0.0001 |
| Birth year | <0.0001 | ||
| 2006–2007 | 543 (7.8%) | 139 (11.2%) | |
| 2008–2009 | 1331 (19.0%) | 119 (9.6%) | |
| 2010–2011 | 1303 (18.6%) | 9 (0.7%) | |
| 2012–2013 | 1369 (19.6%) | 103 (8.3%) | |
| 2014–2015 | 1445 (20.7%) | 249 (20.1%) | |
| 2016–2017 | 1000 (14.3%) | 331 (26.7%) | |
| 2018–2019 | 0 (0.0%) | 291 (23.4%) | |
| Any ROP | 2026 (29.0%) | 502 (40.5%) | <0.0001 |
| PNA at first diagnosed ROP (weeks) | 8.35 (2.22) 8.14 (3.43; 18.71) | 8.07 (2.56) 7.71 (3.14; 19.00) | |
| ROP treatment | 287 (4.1%) | 49 (3.9%) | 0.87 |
| PNA at ROP treatment (weeks) | 12.8 (2.8) 12.4 (7.0; 21.9) | 12.3 (2.4) 11.9 (7.1; 19.6) |
Model development group includes data from Swedish National Registry for ROP, born at GA 24–30 weeks (2007–2017).
Validation groups consist of four external validation cohorts, one from Sweden (later time period than in the model development group), one from Germany and two from USA.
For categorical variables, n (%) is presented. For continuous variables, mean (SD)/median (min; max) is given.
*P values should be interpreted with caution due to the large cohorts. Conclusions should be made based on the clinically relevant differences.
GA, gestational age; PNA, postnatal age; ROP, retinopathy of prematurity; ROP, retinopathy of prematurity; SDS, standard deviation score.