Similar performance of Brasfield and Wisconsin scoring systems in young children with cystic fibrosis

Abstract

Background: To assess the severity of lung disease in cystic fibrosis (CF), scoring systems based on chest radiographs (CXRs), CT and MRI have been used extensively, although primarily in research settings rather than for clinical purposes. It has recently been shown that those based on CXRs (primarily the Brasfield and Wisconsin systems) are as sensitive and valid as those based on CT. The reproducibility and correlation of both systems to pulmonary function tests (PFTs) were recently investigated and were found to be statistically identical. However, the relative performance of these systems has not been specifically assessed in children younger than 5 years old with mild lung disease, a critical age range in which PFTs is rarely performed. Objective: To investigate and compare the performance of the Brasfield and Wisconsin systems in children 0-5 years old with predominantly mild lung disease. Materials and methods: Fifty-five patients 0-5 years old with 105 CXRs were included in the study. Given that the goal was to compare system performance in mild disease, only the first two CXRs from each patient were included (all but five patients had two images). When only one image was available in the target age range, it only was included. Agreement between the Brasfield and Wisconsin systems was assessed using a 2X2 contingency table assuming binary classification of CF lung disease using CXR scoring systems (mild vs. non-mild). In the absence of PFTs or another external gold standard for comparison, the Wisconsin system was used as an arbitrary gold standard against which the Brasfield was compared. Correlation between the two systems was assessed via a concordance correlation coefficient (CCC) for repeated measures. Results: Scores were rated as mild or non-mild based on published numerical cutoffs for each system. The systems agreed on 89/105 (85%) and disagreed on 16/105 (15%) of the CXRs. Agreement between the two systems was statistically significant (P < 0.001). Relative sensitivity and specificity of the Brasfield system (which since using the Wisconsin as the gold standard reflects relative agreement rather than absolute performance of the Brasfield) was also fairly high (85% and 84%, respectively). Relatively high correlation between the two systems was also estimated (r = 0.72). Conclusion: The current study, powered to find at least a mild correlation between the two systems, confirms the Brasfield and Wisconsin systems are in agreement when assessing CF lung disease even in patients younger than 5 years of age with predominantly mild disease.