CRITICAL-EVALUATION OF 3 CHEST RADIOGRAPH SCORES IN CYSTIC-FIBROSIS

Background - A number of chest radiographic scores have been developed to assess the severity of respiratory disease in cystic fibrosis but critical statistical evaluation has been limited. In particular, the c hest radiograph component of the National Institutes of Health (NIH) c linical score has not previously been validated. Three different chest radiograph scores have been compared and the association between them and lung function tests investigated. Methods - The interobserver and intraobserver variation of the Brasfield, NIH chest radiograph, and t he Royal Children's Hospital (RCH) chest radiograph score was assessed by three observers - a paediatric radiologist, a junior and a senior respiratory physician - who independently scored, on separate occasion s, 62 chest radiographs randomly selected from three age strata of pat ients ranging from 7 to 18 years. Lung function tests were available f or 61 patients obtained within three months of the chest radiograph. T wo way analysis of variance was used to estimate components of variati on in scores. Results - Results were similar for the Brasfield and NIH scores, both of which demonstrated greater precision than the RCH sco re, but the estimated repeatability of the Brasfield and NIH scores ca n be expected to differ by up to 20% of the maximum score. The reliabi lities (intraclass correlation) are all reasonably high at 0.74, 0.73, and 0.61 for the Brasfield, NIH, and RCH scores, respectively. The es timated correlation between radiographic scores and lung function test s, adjusted for attenuation caused by measurement error, showed a simi lar correlation for all three scoring methods ranging from 0.55 to 0.7 8. Correlations were slightly greater with FEV(1)% than FVC%. These co rrelations are substantial but not high, indicating that a large propo rtion of the variability in radiographic scores cannot be explained by lung function measurements. Conclusions - The Brasfield and NIH chest radiograph scores have very similar statistical profiles and can be e qually recommended if a chest radiograph score is to be used. The RCH radiographic score appears to be less reliable. The limitations of the se scores need to be understood.