Radiological assessment of small pneumoconiotic opacities.

Problems in the assessment of small opacities, within the ILO U/C International Classification of Radiographs of the Pneumoconioses (International Labour Office, 1972), are discussed in the light of readings by three experts of a group of films in which both rounded and irregular small opacities frequently coexisted. There was considerable disagreement on whether opacities were rounded or irregular, but reasonable agreement on type (diameter or thickness). As expected, rounded opacities were more commonly recorded in upper zones of the lung, and irregular opacities in lower zones. However, determination of which zones were affected left much to be desired. Perhaps as a result, major problems arose over the assessment of combined profusion.