Is chest CT useful in newborn screened infants with cystic fibrosis at 1 year of age?

Abstract

Rationale: Sensitive outcome measures applicable in different centres to quantify and track early pulmonary abnormalities in infants with cystic fibrosis (CF) are needed both for clinical care and interventional trials. Chest CT has been advocated as such a measure yet there is no validated scoring system in infants.

Objectives: The objectives of this study were to standardise CT data collection across multiple sites; ascertain the incidence of bronchial dilatation and air trapping in newborn screened (NBS) infants with CF at 1 year; and assess the reproducibility of Brody-II, the most widely used scoring system in children with CF, during infancy.

Methods: A multicentre observational study of early pulmonary lung disease in NBS infants with CF at age 1 year using volume-controlled chest CT performed under general anaesthetic.

Main results: 65 infants with NBS-diagnosed CF had chest CT in three centres. Small insignificant variations in lung recruitment manoeuvres but significant centre differences in radiation exposures were found. Despite experienced scorers and prior training, with the exception of air trapping, inter- and intraobserver agreement on Brody-II score was poor to fair (eg, interobserver total score mean (95% CI) κ coefficient: 0.34 (0.20 to 0.49)). Only 7 (11%) infants had a total CT score ≥ 12 (ie, ≥ 5% maximum possible) by either scorer.

Conclusions: In NBS infants with CF, CT changes were very mild at 1 year, and assessment of air trapping was the only reproducible outcome. CT is thus of questionable value in infants of this age, unless an improved scoring system for use in mild CF disease can be developed.

Figure 1

Interobserver agreement between initial and rescoring London Cystic Fibrosis Collaboration (LCFC) rounds. CT scores were allocated by scorers A and B for the subset of 22 scans during initial and rescoring rounds. While all 22 pairs of results have been plotted, overlap of some data, particularly those with zero scores means that not all results can be identified individually. Bold circles represent data that overlaid each other, the number in brackets representing the number of infants with each combination of scores. During initial scoring of the subset, scores allocated by scorer B were generally higher than those by scorer A for bronchial dilatation and total scores (A and C). More consistent scores with good agreement were seen for air trapping (B). During rescoring of this subset, scores were more similar, although only fair agreement was again seen for bronchial dilatation (D), while good agreement was seen for air trapping and total scores (E and F). κ=κ coefficient (95% CI). AT, air trapping, BD, bronchial dilatation.

Figure 2

Examples of CT images from infants with cystic fibrosis (CF) showing mild abnormalities in bronchial dilatation and air trapping leading to discrepancy in scoring. (A) An example of thin section CT of the left lung in an infant with CF taken at 1 year of age showing discrepancies in scoring bronchial dilatation (circled). This was scored as normal by scorer A, but mild by scorer B during the initial study round, whereas during the subsequent rescoring round ∼ 8 months later, scorer A scored this as mild bronchial dilatation, while scorer B scored it as normal. (B) Subtle tiny areas of hyperlucency in some of the scattered secondary pulmonary lobules of the lower lobes in keeping with air trapping (ringed by oval). During the initial scoring round, scorer A scored this as mild air trapping while scorer B labelled it as no air trapping. During the rescoring round, both scorers allocated mild air trapping.