OBSERVER VARIATION IN CLASSIFYING CHEST RADIOGRAPHS FOR SMALL LUNG OPACITIES AND PLEURAL ABNORMALITIES IN A POPULATION-SAMPLE

Background The purpose of this study was to assess inter- and intraobs erver variation in the radiographic categories of small lung opacities (profusion) and pleural abnormalities classified according to the ILO classification of pneumoconioses with some modifications. Methods Che ss radiographs derived from a representative adult population sample ( n = 7,095) were classified by two radiologists. Observer variation was assessed on the basis of kappa (kappa)-type statistics. Results The o bservers agreed on profusion categories in 69% of cases of the total m aterial. Up to 98% of the classifications fell into the same category or deviated by no more than one category. The corresponding kappa (kap pa) coefficient was 0.48 (95%CI = 0.46-0.49) and the weighted kappa 0. 72. When a selected subsample was reclassified by the observers, the p roportions of crude agreement on profusion of small opacities ranged f rom 42% to 47% (weighted kappa 0.52-0.55). The proportions of agreemen t on the main pleural abnormalities were 92% or over and the correspon ding kappa coefficients at least 0. 73. Conclusion The classification of lung opacities was subject to considerable observer variation, whic h calls for caution when results from different studies are compared. This variation, however rarely exceeded one category, and thus appears to be small enough for meaningful comparisons between groups, at leas t within a single study. Am. J. Ind. Med. 34:261-265, 1998. (C) 1998 W iley-Liss, Inc.