Azithromycin reduces airway wall thickness in infants: Study

Blood flow to young children’s lungs may be smoother with treatment

Margarida Maia, PhD avatar

by Margarida Maia, PhD |

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Treatment with the antibiotic azithromycin reduces abnormal thickening of the walls of bronchi — air passages leading to the lungs — in young children with cystic fibrosis (CF), and this may translate into smoother blood flow to the lungs, a study suggests.

Data come from COMBAT-CF (NCT01270074), a Phase 3 clinical study in Australia and New Zealand that tested how well azithromycin works to prevent the onset of bronchiectasis, an abnormal widening of the bronchi, in the first three years of life. 

The study, “Azithromycin reduces bronchial wall thickening in infants with cystic fibrosis,” was published in the Journal of Cystic Fibrosis.

In CF, thick mucus builds up in the lungs and blocks the airways, making it hard to breathe and clear away infection. Bronchiectasis occurs when the airways become damaged, often upon repeated infection, causing them to widen.

While in COMBAT-CF azithromycin failed to meet a goal of reducing the proportion of children who at age 3 showed signs of bronchiectasis on CT scans, it was better than a placebo at shortening the time spent in the hospital and reducing the need for other antibiotics.

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Azithromycin reduced thickening for infants, AI analysis shows

Researchers in Australia and the Netherlands ran a new analysis in which CT scans were read using a fully automatic artificial intelligence (AI)-based method that measures the inner and outer diameters, as well as the thickness, of the bronchi and arteries that supply the lungs to see if the bronchi are widening or thickening.

The study involved 66 children who had been given azithromycin and 59 who had been assigned to the placebo in the COMBAT-CF study. There were a total of 122 CT scans obtained at one year and 106 CT scans at three years that had enough quality for the analysis.

In azithromycin-treated children, bronchial wall thickening was reduced, and the inner bronchial diameter relative to an artery’s diameter was higher than in placebo-administered children. Additionally, the bronchial outer wall to artery ratio was higher, mainly because the arteries had reduced diameters. 

Another AI-based system measured low attenuation regions, or trapped air in blocked airways. Arterial diameter was significantly linked to low attenuation regions in the placebo group but not in the azithromycin group.

“Automatic measurements of bronchial dimensions add clinically relevant information,” the researchers wrote, noting that the AI-based method is possibly more accurate than PRAGMA-CF, the method used in the previous analysis.

“This positive effect [in bronchial wall thickening] was not detected by PRAGMA-CF as the human eye is not very accurate and sensitive to assess bronchial wall thickness,” they wrote. Fully automated readings, they added, allow a large number of measurements to be computed “with great sensitivity and accuracy.”

“Azithromycin-treated infants with CF show a reduction in bronchial wall thickness and possibly a positive effect on lung perfusion,” the researchers concluded, noting that these data support the use of maintenance treatment with azithromycin.