Table 5. Results for the multivariate logistic regression model of BPD, with terms for the reduced set of baseline predictors and the longitudinal factors selected by the stepwise process.

Model terms	Odds ratio (95% confidence interval)a	P valueb
Baseline predictors
Birth weight	0.87 (0.76, 0.99)	0.037
SNAPc	0.78 (0.56, 1.10)	0.15
SNAP squared	0.83 (0.37, 1.87)	0.65
Male	1.39 (0.77, 2.51)	0.27
Apgar score <7 at 5 min	1.56 (0.81, 3.01)	0.18
Longitudinal predictors
Paco2 >50 torr
Intercept for AUC >0 (vs. AUC = 0)	2.65 (1.29, 5.45)	0.0078
AUC (linear)	1.00 (0.71, 1.40)	0.99
Joint test			0.024
MAP >0 cm H2O
intercept for AUC >0 (vs. AUC = 0)	1.00 (0.29, 3.43)	1.00
AUC (linear)	2.33 (1.56, 3.47)	<0.0001
Joint test			<0.0001

SNAP score for neonatal acute physiology, AUC area under the curve (for the first 6 days after admission); Paco₂ partial pressure of carbon dioxide, MAP mean airway pressure

N = 419 (six infants were excluded for missing Apgar score or MAP AUC); lack of fit was nonsignificant (P = 0.87) by the Hosmer–Lemeshow test; area under the Receiver Operating Characteristic curve was 0.838

^aOdds ratios are adjusted for the other factors in the model. Odds ratios for continuous predictors correspond to the following unit changes: birth weight, 100 g; AUCs (linear terms), one standard deviation computed among those with AUC >0; others, one standard deviation

^bOne degree of freedom Wald chi-square test; joint test for AUCs based on a two degree of freedom Wald chi-square test of the indicator variable for AUC >0 and the linear term for the AUC

^cResults for SNAP are from a reduced model with the SNAP squared term excluded