Table 1.

Demographic data for cases used in the principal phenotype and the refined phenotype

	Principal phenotype Median (mean)	Refined phenotype (age-limited) Median (mean)
Duration of admission (days)	4 (5.3)	4 (4.9)
Weight on admission (kg)	5.15 (5.47)	5.03 (5.18)
Age on admission (weeks)	10 (15.6)	8 (9.1)
RSV positive (%)	100%	100%
Oxygen used (%)	88%	86%
Duration of oxygen (days)	3 (3.78)	3 (3.6)
Tube feeding required (%)	60.9%	61.7%
Intravenous fluids required (%)	32.1%	31.9%
Ventilation required (%)	23.7%	14.5%
Parental smoking (%)	36.6%	33.7%
Number of older siblings	1 (1.19)	1 (1.19)
Gestation (weeks)	39 (38)	40 (39.4)
Pre-existing heart condition (%)	5.5%	0.0%
Pre-existing lung condition (%)	5.9%	0.0%
Oxygen-dependent CLD (%)	2.0%	0.0%

CLD, chronic lung disease; RSV, respiratory syncytial virus.