Radiology: CT elucidates long-term cystic fibrosis complications

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A study in the August issue of Radiology found that that there is a strong relationship-confirmed through the use of CT--between the severity of bronchiectasis in children with cystic fibrosis (CF) and respiratory infection with mucoid pseudomonas aeruginosa (PA).

Philip M. Farrell, MD, from the department of pediatrics at the University of Wisconsin in Madison, and colleagues pointed out that bronchiectasis is an early feature of CF lung disease, considered to be irreversible, and indicates there is permanent damage to the lungs. Consequently, the authors said that preventing bronchiectasis in young CF children is critical, and attempts to combat bronchiectasis should include reducing exposure to and the early eradication of PA.

The authors examined patients who enrolled in the Wisconsin trial of newborn screening from 1985 to 2009, with thin-section chest CT, used in a prospective cross-sectional design to study patients ranging in age from 6.6 to 17.6 years. Eighty-two patients participated in the thin-section CT study, 68 of whom (83 percent) showed bronchiectasis of varying severity. According to the authors, of 12 potential risk factors, only respiratory infection with mucoid PA correlated significantly with bronchiectasis.

The investigators also pointed out that while pulmonary function tests (PFT) have been the most widely used means of assessing CF lung disease, their findings support the idea that CT scanning is the best method to identify and quantitate bronchiectasis in order to assess the determinants of bronchiectasis in young CF patients.

"That the use of CT scanning should find a greater correlation of mucoid with the severity of bronchiectasis than PFTs shouldn't be surprising," the authors said, "since PFTs depend on the behavior of the entirety of both lungs, while the anatomic localization provided by using CT allows reliable identification of disease affecting as little as a single bronchopulmonary segment."

They found that, in young children, chest imaging is approximately four times more sensitive than PFTs for evaluating CF lung disease.

While there is the risk of radiation exposure involved with CT scanning, Farrell and colleagues recorded a dose of .55 mSv in this study, but they noted that changes in technique could still result in adequate image quality while reducing radiation exposure by 30 percent.

As for the clinical implications of the study, the researchers concluded that since bronchiectasis can develop early in infancy, this adds to the argument for newborn screening, as well as aggressive care when it comes to avoiding chronic and mucoid PA infections in young CF patients.