Drop-out and missing data analysis in EPICure and EPICure2
| EPICure 1995 | EPICure2 2006 | P value (a) vs (b) | P value (c) vs (d) | P value (b) vs (d) | ||||
| 2.5-year sample without complete HUI data at 11 years* (a) | 2.5-year sample with complete HUI data at 11 years (b) | 3-year sample without complete HUI data at 11 years* (c) | 3-year sample with complete HUI data at 11 years (d) | |||||
| n=120 | n=140 | n=496 | n=88 | |||||
| Perinatal variables | ||||||||
| Gestational age | ||||||||
| <24 weeks | % (n/N) | 8.3 (10/120) | 10.0 (14/140) | 11.3 (56/496) | 11.4 (10/88) | 0.895 | 0.342 | 0.467 |
| 24 weeks | % (n/N) | 32.5 (39/120) | 31.4 (44/140) | 31.5 (156/496) | 23.9 (21/88) | |||
| 25 weeks | % (n/N) | 59.2 (71/120) | 58.6 (82/140) | 57.3 (284/496) | 64.8 (57/88) | |||
| Birth weight (g) | Mean (SD) | 739.7 (112.8) (n=120) | 755.4 (107.3) (n=140) | 732.6 (120.6) (n=496) | 750.2 (118.2) (n=88) | 0.252 | 0.206 | 0.733 |
| Multiple birth | % (n/N) | 19.2 (23/120) | 31.4 (44/140) | 21.8 (108/496) | 23.9 (21/88) | 0.024 | 0.663 | 0.218 |
| Maternal age at delivery | Mean (SD) | 28.1 (6.2) (n=120) | 28.8 (5.7) (n=139) | 29.1 (6.4) (n=496) | 30.8 (6.1) (n=88) | 0.337 | 0.020 | 0.013 |
| Breast milk at any time | % (n/N) | 80.8 (97/120) | 88.6 (124/140) | 95.4 (472/495) | 100.0 (88/88) | 0.082 | 0.039 | 0.001 |
| Enteral feeding begun before day 7 | % (n/N) | 43.7 (52/119) | 51.1 (69/135) | 81.7 (405/496) | 85.2 (75/88) | 0.238 | 0.419 | <0.001 |
| Antenatal systemic steroids | % (n/N) | 76.7 (92/120) | 82.7 (115/139) | 87.4 (429/491) | 90.9 (80/88) | 0.224 | 0.349 | 0.085 |
| Postnatal systemic steroids | % (n/N) | 73.3 (88/120) | 69.8 (97/139) | 19.6 (97/496) | 25.0 (22/88) | 0.528 | 0.243 | <0.001 |
| Demographic variables | ||||||||
| Age assessed at 11 years | Mean (SD) | – | 10.8 (0.3) (n=140) | – | 11.8 (0.5) (n=88) | – | – | <0.001 |
| Male sex | % (n/N) | 55.0 (66/120) | 43.6 (61/140) | 47.2 (234/496) | 52.3 (46/88) | 0.066 | 0.378 | 0.200 |
| Ethnicity | ||||||||
| White | % (n/N) | 66.7 (80/120) | 79.1 (110/139) | 63.3 (311/491) | 60.5 (52/86) | 0.051 | 0.290 | 0.002 |
| Asian | % (n/N) | 10.8 (13/120) | 4.3 (6/139) | 9.6 (47/491) | 16.3 (14/86) | |||
| Black | % (n/N) | 19.2 (23/120) | 15.8 (22/139) | 22.6 (111/491) | 18.6 (16/86) | |||
| Other | % (n/N) | 3.3 (4/120) | 0.7 (1/139) | 4.5 (22/491) | 4.7 (4/86) | |||
| Maternal education | ||||||||
| Low | % (n/N) | 25.5 (24/94) | 10.1 (14/138) | 9.0 (21/233) | 4.9 (4/82) | 0.007 | 0.111 | <0.001 |
| Medium | % (n/N) | 61.7 (58/94) | 76.8 (106/138) | 60.1 (140/233) | 52.4 (43/82) | |||
| High | % (n/N) | 12.8 (12/94) | 13.0 (18/138) | 30.9 (72/233) | 42.7 (35/82) | |||
| IMD at 11 years | Mean (SD) | – | 5.3 (2.8) (n=138) | – | 5.2 (2.8) (n=87) | – | – | 0.814 |
| Developmental variables | ||||||||
| IQ score at 2.5/3 years | Mean (SD) | 76.1 (14.7) (n=75) | 83.6 (13.3) (n=132) | 86.4 (20.1) (n=250) | 85.5 (19.1) (n=75) | <0.001 | 0.719 | 0.405 |
| Severe neurodevelopmental impairment at 2.5/3 years | % (n/N) | 32.3 (31/96) | 15.8 (22/139) | 16.8 (42/250) | 14.7 (11/75) | 0.003 | 0.661 | 0.823 |
| IQ score at 11 years | Mean (SD) | – | 85.8 (16.4) (n=138) | – | 82.2 (19.9) (n=88) | – | – | 0.142 |
| Severe neurodevelopmental impairment at 11 years | % (n/N) | – | 7.9 (11/140) | – | 5.7 (5/88) | – | – | 0.327 |
*This could be due to drop out, non-completion of parent questionnaires or missing values in one or more of the eight attributes required to compute the utility score.
HUI, Health Utilities Index; IMD, index of Multiple Deprivation.