Univariable analysis of factors associated with screening compliance for infants in neonatal units during screening period
| Characteristic | ROP screening status | p Value | Pairwise comparisons with corrected p<0.05* | |||
|---|---|---|---|---|---|---|
| On-time (1) | Early (2) | Late (3) | Unknown (4) | |||
| (n=6782) | (n=2886) | (n=4010) | (n=2733) | |||
| Gestation (completed weeks) Median (IQR) range | 29 (28–31) 22–37 | 30 (28–31) 22–37 | 28 (26–30) 22–37 | 30 (29–31) 23–37 | <0.001† | All |
| Birth weight (g) | 1210 (980–1430) | 1270 (1050–1450) | 1080 (870–1320) | 1360 (1150–1542) | <0.001‡ | All |
| Median (IQR), range | 383–2530 | 399–2580 | 392–2440 | 440–2705 | ||
| Sex | ||||||
| Female, n (%) | 3283 (48.4) | 1424 (49.3) | 1879 (46.9) | 1285 (47.0) | 0.122 | N/A |
| Male, n (%) | 3498 (51.6) | 1457 (50.5) | 2128 (53.1) | 1447 (53.0) | ||
| Missing, n (%) | 1 (0.01) | 5 (0.2) | 3 (0.1) | 1 (0.04) | ||
| Ethnicity | ||||||
| White, n (%) | 4787 (70.6) | 1968 (68.2) | 2975 (74.2) | 2002 (73.3) | <0.001 | (1)–(3),(1)–(4), |
| Non-white, n (%) | 1767 (26.1) | 784 (27.2) | 872 (21.6) | 600 (22.0) | (2)–(3),(2)–(4) | |
| Missing, n (%) | 228 (3.4) | 134 (4.6) | 163 (4.1) | 131 (4.8) | ||
| Pregnancy | ||||||
| Singleton, n (%) | 4838 (71.3) | 2096 (72.6) | 2927 (73.0) | 1979 (72.4) | 0.245 | N/A |
| Multiples, n (%) | 1943 (28.7) | 790 (27.4) | 1081 (27.0) | 753 (27.6) | ||
| Missing, n (%) | 1 (0.01) | 0 (0.0) | 2 (0.1) | 1 (0.04) | ||
| Antenatal steroids | ||||||
| Yes, n (%) | 5614 (82.8) | 2356 (81.6) | 3214 (80.2) | 1946 (71.2) | 0.011 | (1)–(4),(3)–(4) |
| No, n (%) | 699 (10.3) | 310 (10.7) | 392 (9.8) | 484 (17.7) | ||
| Missing, n (%) | 469 (6.9) | 220 (7.6) | 404 (10.1) | 303 (11.1) | ||
| Mode of delivery | ||||||
| Vaginal, n (%) | 2491 (36.7) | 947 (32.8) | 1541 (38.4) | 854 (31.3) | <0.001 | (1)–(2),(1)–(3), |
| Caesarean, n (%) | 3923 (57.8) | 1781 (61.7) | 2118 (52.8) | 1637 (59.9) | ||
| Missing, n (%) | 368 (5.4) | 158 (5.5) | 351 (8.8) | 242 (8.9) | (1)–(4),(2)–(3), (3)–(4) | |
| Days of intensive care prior to start of screening window | 5 (2–13) | 4 (2–8) | 8 (4–22) | 3 (1–5) | <0.001† | All |
| Median (IQR) range | (0–50) | (0—51) | (0—51) | (0–47) | ||
| Days of mechanical ventilation prior to start of screening period | 1 (0–4) | 0 (0—2) | 2 (0–7) | 0 (0–2) | <0.001† | All |
| Median (IQR) range | (0–50) | (0—51) | (0–48) | (0–47) | ||
| Days of oxygen therapy prior to start of screening period | 2 (0–9) | 1 (0–7) | 4 (1–12) | 1 (0–4) | <0.001† | All |
| Median (IQR) range | (0–47) | (0–40) | (0–46) | (0–40) | ||
| Transferred in week before or during screening period | (1)–(3),(2)–(3), | |||||
| Yes, n (%) | 578 (8.5) | 240 (8.3) | 467 (11.7) | 203 (7.4) | <0.001 | (3)–(4) |
| No, n (%) | 6204 (91.5) | 2646 (91.7) | 3543 (88.4) | 2530 (92.6) | ||
| Unit level | ||||||
| 1, n (%) | 736 (10.9) | 423 (14.7) | 467 (11.7) | 580 (21.2) | <0.001 | All |
| 2, n (%) | 2772 (40.9) | 1208 (41.9) | 1635 (40.8) | 1268 (46.4) | ||
| 3, n (%) | 3274 (48.3) | 1255 (43.5) | 1908 (47.6) | 885 (32.4) | ||
| Number of intensive care days provision | ||||||
| <500, n (%) | 2236 (33.0) | 1091 (37.8) | 1467 (36.6) | 1373 (50.2) | <0.001 | (1)–(2), (1)–(4), (2)–(3),(2)–(4), (3)–(4) |
| 500–999, n (%) | 1222 (18.0) | 548 (19.0) | 613 (15.3) | 407 (14.9) | ||
| 1000–1999, n (%) | 1251 (18.5) | 554 (19.2) | 911 (22.7) | 472 (17.3) | ||
| ≥2000, n (%) | 2073 (30.6) | 693 (24.0) | 1019 (25.4) | 481 (17.6) | ||
*Pairwise comparisons of screening status groups show associations with p<0.05 after Bonferroni correction for multiple testing
†Indicates p value from Kruskal–Wallis test.
‡Indicates p value from regression with robust standard errors for unequal variance
ROP, Retinopathy of Prematurity.