Background: Whole airway wall thickening on high resolution computed tomography (HRCT) is
reported to parallel thickening of the bronchial epithelial reticular basement membrane (RBM) in
adult asthmatics. A similar relationship in children with difficult asthma (DA), in whom RBM
thickening is a known feature, may allow the use of HRCT as a non-invasive marker of airway
remodelling. We evaluated this relationship in children with DA.
Methods: 27 children (median age 10.5 [range 4.1–16.7] years) with DA, underwent
endobronchial biopsy from the right lower lobe and HRCT less than 4 months apart. HRCTs were
assessed for bronchial wall thickening (BWT) of the right lower lobe using semi-quantitative and
quantitative scoring techniques. The semi-quantitative score (grade 0–4) was an overall assessment
of BWT of all clearly identifiable airways in HRCT scans. The quantitative score (BWT %; defined
as [airway outer diameter – airway lumen diameter]/airway outer diameter ×100) was the average
score of all airways visible and calculated using electronic endpoint callipers. RBM thickness in
endobronchial biopsies was measured using image analysis. 23/27 subjects performed spirometry
and the relationships between RBM thickness and BWT with airflow obstruction evaluated.
Results: Median RBM thickness in endobronchial biopsies was 6.7(range 4.6 – 10.0) µm. Median
qualitative score for BWT of the right lower lobe was 1(range 0 – 1.5) and quantitative score was
54.3 (range 48.2 – 65.6)%. There was no relationship between RBM thickness and BWT in the right
lower lobe using either scoring technique. No relationship was found between FEV1 and BWT or
RBM thickness.
Conclusion: Although a relationship between RBM thickness and BWT on HRCT has been found
in adults with asthma, this relationship does not appear to hold true in children with DA.