ILO Classification

The ILO International Classification of Radiographs of Pneumoconioses is a system of classifying chest radiographs (X-rays) for persons with a (or, rarely, more than one) form of pneumoconiosis. The intent is to provide a standardized, uniform method of interpreting and describing abnormalities in chest x-rays that are thought to be caused by prolonged dust inhalation. In use, it provides a system for both epidemiological comparisons of many individuals exposed to dust and evaluation of an individual's potential disease relative to established standards.

Since 1946, the International Labour Organization has been a specialized agency of the United Nations, with objectives including establishing and overseeing international labor standards and labor rights. The International Labour Office ("ILO") is the Organization’s research body and publishing house. Since 1950, the ILO has periodically published guidelines on how to classify chest X-rays for pneumoconiosis. The purpose of the Classification was to describe and codify radiographic abnormalities of the pneumoconioses in a simple, systematic, and reproducible manner, aiding international comparisons of data, epidemiology, screening and surveillance, clinical purposes, and medical research. The most recent edition of the Guidelines, completed in 2011, replaced the 2000 revised edition.

In 1974, after studies of surveillance programs for coal miners revealed unacceptable degrees of interreader variability, the National Institute for Occupational Safety and Health (NIOSH),began the "B" reader program (so named because of the Black lung or Coal Workers' X-ray Surveillance Program), with the intent to train and certify physicians in the ILO Classification system. The "B" reader certification examination went into full operation in 1978. A physician must pass the certification examination to be a "B" reader.

The ILO Classification system includes the printed Guidelines and sets of standard radiographs, available in both film and, as of 2011, digital forms. The reader compares the subject chest X-ray (only the appearances seen on postero-anterior, or PA, chest x-ray) with those of the standard set. The standard radiographs provide differing types ("shape and size") and severity ("profusion") of abnormalities seen in persons with pneumoconiosis, including Coal Workers’ Pneumoconiosis, silicosis, and asbestosis. The reader then classifies the subject x-ray, often recording the findings on the NIOSH Roentgenographic Interpretation form. The ILO Classification system pertains to pulmonary parenchymal abnormalities (small and large opacities), pleural changes (pleural plaques, calcification, and diffuse pleural thickening) and other features associated, or sometimes confused, with occupational lung disease.

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