Lung hyperinflation quantitated by chest CT in children with bronchiolitis obliterans syndrome following allogeneic hematopoietic cell transplantation.

OBJECTIVES

Bronchiolitis obliterans syndrome (BOS) diagnosis in children following allogeneic hematopoietic stem cell transplantation (post-HSCT) is based on detection of airway obstruction on spirometry and air-trapping, small airway thickening or bronchiectasis on chest CT. We assessed the relationship between spirometry indices and low-attenuation lung volume at total lung capacity (TLC) on CT.

METHODS

Data of children post-HSCT with and without BOS were analyzed. An age-specific, low-attenuation threshold (LAT) was defined as average of (mean-1SD) lung parenchyma attenuation of 5 control subjects without lung disease matched to each age subgroup of post-HSCT patients. % CT lung volume at TLC with attenuation values <LAT was calculated. Association between % lung volume with low attenuation and FEV/FVC was assessed.

RESULTS

Twenty-nine children post-HSCT were referred to exclude BOS and 12 of them had spirometry and an analyzable chest CT. We studied: (i) 6 children post-HSCT/BOS (median age: 8.5 years [IQR 7, 15]; median FEV/FVC z-score: -2.60 [IQR -2.93, -2.14]); (ii) 6 children post-HSCT/no BOS (age: 13.5 years [9.8, 16.3]; FEV/FVC z-score: 0.44 [-0.30, 2.10]); and (iii) 40 controls without lung disease (age:11 years [8.3, 15.8]). Patients post-HSCT/BOS had significantly higher % lung volume with low attenuation than patients post-HSCT/no BOS: median % volume 16.4% (7.1%, 37.2%) vs. 0.61% (0.34%, 2.79%), respectively; P = .004. An exponential model described the association between % CT lung volume below LAT and FEV/FVC z-score (r = 0.76; P < .001).

CONCLUSION

In children post-HSCT with BOS, low-attenuation lung volume on chest CT is associated with airway obstruction severity as expressed by FEV/FVC z-score.