Radiographic grading of extrinsic allergic alveolitis. A comparison between a modified ILO classification and a...

We analyzed the acute phase radiographs of 107 consecutive patients with clinically confirmed extrinsic allergic alveolitis. Three readers independently recorded the profusion and the type of opacities according to the standard ILO criteria extended with categories x, y, z, and ground glass for description as proposed by McLoud et al. The profusion of the changes was grade 0 in 13%, grade 1 in 37%, grade 2 in 35%, and grade 3 in 15% of the interpretations. The type of predominant small opacities was p in 33%, x in 22%, s in 13%, t in 10%, q in 9%, and 0, r, u, y, and z in 13% of the interpretations. Ground glass density was seen in 8% of the recordings. The changes were predominantly located in the middle and lower lung zones. For comparison, according to the classification of Hapke et al. miliary changes (68%) predominated over fibrotic (27%) and normal (11%) recordings. The intraobserver agreement was good by both methods, but there was less interobserver variation with the ILO method. The semiquantitative standardized modified ILO scheme was considered more informative than Hapke's descriptive classification for epidemiologic and research purposes.