Validation of a new Japanese classification for predicting severe bronchopulmonary dysplasia in preterm infants

Bronchopulmonary dysplasia (BPD) is the most prevalent chronic lung disease in very preterm infants; however, conventional classifications have limited ability to predict severity before 36 weeks' postmenstrual age (PMA). A new Japanese classification, based on small for gestational age (SGA), bubbly/cystic chest radiographic findings, and chorioamnionitis (CAM), was proposed to enable earlier risk stratification. However, its validation in homogeneous cohorts is warranted.

This study aimed to examine the association between this new Japanese classification and severe BPD development at 36 weeks' PMA in a secondary analysis of a randomized controlled trial (RCT).

A retrospective secondary analysis of a multicenter, double-blind RCT of inhaled corticosteroids in 12 tertiary neonatal intensive care units in Japan (2006-2009) was performed. Infants with a birth weight (BW)<1,000 g and requiring mechanical ventilation were enrolled. Of those 211 infants, 194 survivors were analyzed. Severe BPD was defined by National Institute of Child Health and Human Development criteria as requiring supplemental oxygen (fraction of inspired O2 >0.30) or positive pressure ventilation at 36 weeks' PMA. Logistic regression analyses were adjusted for gestational age, BW, sex, Apgar score, maternal steroid use, respiratory distress syndrome, and patent ductus arteriosus.

Among the 194 infants, 25 were SGA, 45 had bubbly/cystic findings, and 86 had CAM. Severe BPD occurred in 80 infants. A multivariate analysis identified SGA (adjusted odds ratio [aOR], 3.32; 95% confidence interval [CI], 1.16-9.48; P=0.032) and bubbly/cystic findings (aOR, 10.88; 95% CI, 4.43-26.72; P<0.01) as independent risk factors. Compared with type II (non-CAM, no bubbly/cystic findings), type I (bubbly/cystic only: aOR, 6.21; 95% CI, 1.93-14.36) and type III (CAM plus bubbly/cystic: aOR, 15.32; 95% CI, 2.48-46.32) were significantly associated with severe BPD.

The new Japanese classification demonstrated that SGA and bubbly/cystic findings at day 28 independently predicted severe BPD. Early stratification using this classification may facilitate the early identification of high-risk infants for targeted interventions.