Chest CTs in primary ciliary dyskinesia: Not too few, but not too many!

Over the last decades, chest computed tomography (CT) has gained increasing importance in identifying and monitoring pediatric and adult lung diseases, and is considered an invaluable tool for clinical management and intervention studies. CT scoring systems have been developed in order to quantify both extent and severity of cystic fibrosis (CF) and non-CF lung disease. Recently, an important prognostic value for severe interstitial lung diseases, namely idiopathic pulmonary fibrosis, has been also attributed to CT scores, and CT is currently recommended as a major outcome before listing these patients for lung transplantation. Despite its relevance in the characterization of lung abnormalities, the role of CT in the assessment of disease progression is still debated. Particularly, major concerns have been raised due to the ionizing radiation burden of CT and the possible consequences of cumulative doses deriving from frequent follow-up examinations, especially in children. In CF, the most paradigmatic example of chronic suppurative lung disease affecting Caucasian children and adolescents, chest CT scores decline more rapidly than lung function parameters. A significant correlation has also been demonstrated between CT scores and subsequent measures of lung disease severity, including respiratory infectious exacerbations. Therefore, CT has been proposed as a useful tool to identify CF children at higher risk for lung disease progression. Finally, a recent multicenter study of 411 CF patients screened for lung transplantation showed that chest CT significantly correlates with survival prediction models, and that these can be potentially improved by CT findings. In primary ciliary dyskinesia (PCD), a suppurative lung disorder with good life expectancy and much better prognosis than CF, evidences for routine use of chest CT appear weaker. A Task Force from the European Respiratory Society has recently emphasized that, despite high-resolution CT is used to define the extent of bronchiectasis and can monitor the disease progression, there is less evidence that regular CT affects pulmonary outcome in PCD than there is for CF. Particularly, no agreement has been achieved on the optimal time interval that should be kept between CT scans. Nevertheless, some good quality clinical studies have been published on this issue that reflect an increasing interest in the use of CT in the care of patients with PCD. Two recent articles in the Journal have addressed the relationship between lung function tests and CT scans. In the first, a group of Italian patients with PCD underwent spirometry and chest CT at two different time points, i.e., in stable and unstable lung disease, respectively. The most striking finding was that, at the second evaluation, i.e., when symptoms and signs indicated that a clinical deterioration occurred, CT score worsened, while spirometry did not change significantly, or might even have improved, when compared to the first assessment. These data suggest that spirometry may be less accurate than CT in detecting changes associated with progression of PCD lung disease. In the second, Lemery-Magin and colleagues, from France, further delved into this issue extending and completing the results of the Italian study. They found a