Variability in interpretation of radiographs for asbestosis abnormalities: problems and solutions

Interobserver variation continues to be a substantial problem for interpretation of asbestos-workers' X-rays, despite incremental improvements in the International Labour Office (ILO) classification system. The apparent degree of agreement/variability is affected by the population disease prevalence. For most populations, experts will be able to agree routinely about normal films. Yet designed trials show that selected experts exhibit a two-fold or greater range for perceived prevalence of abnormal profusions. This degree of variability would be adequate for many population studies were it achieved under real-life conditions of interpretation. Unfortunately, the realistic degree of interobserver variability is probably much higher under actual population surveillance conditions. Asbestos population surveillance programs have provided little or no quality assurance for ILO interpretations, so the very high variability suggested by available data are not surprising and are not the fault of the classification. Recommendations include required participation in quality-assurance panels for those who wish to be certified as interpreters, with consistent feedback and the dropping of outliers. If quality-assurance programs are implemented, the classification will achieve its intended epidemiologic purposes.