International Classification of Radiographs of Pneumoconiosis 1971

Our plain-English summary of International Classification of Radiographs of Pneumoconiosis 1971, by International Labor Office (1972).

The study

• Author: International Labor Office
• Published: International Labor Office. Geneva (1972)
• Type of article: Report
• Our copy: from Johns-Manville's own medical library. The article is still under copyright, so we describe it here rather than post it.

In plain English

This is not a research study but an International Labour Office (ILO) guide to its 1971 system for classifying chest X-rays of pneumoconioses, dust-related lung diseases including asbestosis. Readers compare each film with standard films. The 1971 revision added three categories of 'irregular small opacities' to the short scheme. These are linear or net-like shadows of the kind seen in asbestos workers. The extended scheme grades small opacities on a 12-point scale instead of a 4-point one. It grades the width and length of chest-wall pleural thickening separately. It records costophrenic angle filling separately and grades pleural calcification apart from thickening. It also records an ill-defined heart outline, setting grade 1 fairly high to exclude poor definition of the extreme tip of the left cardiac outline from other causes, such as cardiac fat pads. A well-marked shaggy mediastinal shadow was called highly characteristic of asbestosis. It stated that the categories form a continuum, with no sharp line between normal and disease. It acknowledged that links between irregular opacities and dust exposure, lung function and death were less well established than for rounded opacities.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Classification and guidance document (International Labour Office radiograph classification scheme with notes on its use); not a study of patients or workers
• Who was studied: No study population. The document covers how to classify chest radiographs (X-ray films) of pneumoconioses, judged against standard reference films.
• Exposure: No exposure was measured. The scheme is meant for films of asbestos workers and of other pneumoconioses, including silicosis, coalworkers' pneumoconiosis, mixed dust and diatomite pneumoconiosis. The document lists asbestos, tremolite, talc and some other minerals among the causes of pleural calcification.
• Main results:
  • The 1971 short scheme introduced three categories (1, 2, 3) of irregular small opacities, with standard films provided.
  • The complete (extended) classification grades rounded and irregular small opacities on a 12-point scale instead of a 4-point scale. For example, a film judged category 2 for which category 1 was seriously considered is recorded as 2/1.
  • The document stated that the categories express a continuum from an exceptionally normal film to advanced category 3, with no sharp boundary between normal and pneumoconiosis.
  • For pleural thickening along the chest wall, the 1971 scheme grades the maximum width and the combined length of the shadows separately.
  • Filling of the costophrenic angle is recorded separately from pleural thickening elsewhere. A lower-limit standard film is provided, but its degree is not graded.
  • Pleural calcification is graded separately from pleural thickening.
  • The document described a well-marked shaggy appearance of the mediastinal shadow as highly characteristic of asbestosis. Separately, grade 1 for an ill-defined heart outline is set fairly high to exclude poor definition of the extreme tip of the left cardiac outline from other causes, such as cardiac fat pads.
  • Large opacities in asbestosis were described as having much less well-defined edges than those typical of silicosis and coalworkers' pneumoconiosis. They can be recorded as ill-defined or well-defined.
  • When used for epidemiological purposes on groups of films, it was said to be practicable to classify 200 to 500 films a day with the complete classification.
• The authors' conclusion: The document stated that the more detailed features were introduced mainly to describe asbestosis, but that the complete scheme should not be regarded as useful only for that purpose.
• Limitations the authors state:
  • The document stated that the relationship of irregular (linear) opacities to dust exposure, lung function and mortality is less well established than for rounded opacities.
  • The document stated that further research is needed to validate classifying the heart and diaphragm outlines in this way.
  • The document stated that classifying such diverse features inevitably involves some oversimplification of a pattern that different observers may see differently.

Topics

Medical terms in this study, explained in our Lexicon: Pneumoconiosis, Chest X-Ray, Pleural Thickening, Costophrenic angle, Pleural Calcification.

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