Cord blood KL-6, a specific lung injury marker, correlates with the subsequent development and severity of atypical bronchopulmonary dysplasia

Background: A considerable number of preterm infants may have been exposed to inflammation in utero and may be born with an inflamed lung. Objectives: To determine the impact of antenatal lung injury and inflammatory response on the pathogenesis of bronchopulmonary dysplasia (BPD) according to its clinical pattern, using KL-6 (as a lung injury marker) and C-reactive protein (CRP) (as a marker of inflammatory response). Methods: In this case-control study, a total of 74 infants (<32 weeks of gestation) including BPD with minimal early lung disease ('atypical'; 21 infants), BPD with significant early lung disease ('classic'; 29 infants) and the non-BPD (24 infants) groups underwent KL-6 and CRP in cord blood determinations. Results: The cord plasma KL-6 levels were significantly higher in the atypical and the total BPD groups than in the non-BPD group (median = 60.9 vs. 34.5 U/ml, p = 0.031; 43.5 vs. 34.5 U/ml, p = 0.02). However, the cord plasma CRP levels were not significantly different among the study groups. The cord plasma KL-6 levels in patients with atypical BPD were significantly higher in infants with moderate or severe BPD than in infants with mild BPD (median = 88.3 vs. 41.5 U/ml, p = 0.041) and were found to be significantly correlated with the duration of oxygen therapy (r = 0.502, p = 0.024). Conclusions: The present study shows that cord plasma KL-6, a specific lung injury marker, is increased and objectively reflects disease severity in atypical BPD.