Unraveling the Tapestry of Radiographic Evaluation in Pneumoconiosis: Exploring the Intricacies of the International Labor Organization Classification (2022) for Radiographic Evaluation

INTRODUCTION

The International Labor Organization (ILO) has released yet another edition of its international classification of radiographs for pneumoconiosis, claiming it to be an indispensable epidemiological tool. They emphasize the significant updates made since the previous edition, suggesting their importance. However, one question that continuously crops up in scientific committee discussions that whether this classification truly deserves to be hailed as the differential diagnostic tool for pneumoconiosis. Is it genuinely infallible and the definitive authority on providing a differential diagnosis for this condition?

Pneumoconiosis is a group of lung diseases caused by the lung’s reaction to inhaling certain specks of dust. The leading cause of pneumoconiosis is workplace exposure. Environmental exposures have rarely been related to these groups of diseases.¹ These diseases typically take many years to develop. However, rapidly progressive forms of silicosis, one type of Pneumoconiosis, can occur after short periods of intense exposure.¹ When severe, the diseases often lead to lung impairment, disability, and premature death. From a public health perspective, these conditions are entirely man-made and can be avoided through appropriate preventive measures.

In developing countries, the incidence and prevalence of pneumoconioses are high and appear to be increasing. The rapid expansion of mining, mineral extraction, construction, and other industries puts many new workers at risk yearly. The hygienically poor working conditions often expose workers to high concentrations of respirable dust, so pneumoconioses can develop rapidly after a short latency period. The health risk is increased by the high prevalence of tuberculosis in most of those countries.² Silicosis is now an emerging health issue with a high fatality rate in developed countries such as Australia, New Zealand, and the United States among the engineered stone fabricated workers. Despite the life-threatening consequences of pneumoconiosis, workers working in various industries choose their work over their health due to their socioeconomic constraints, thus increasing the menace of this deadly group of disorders. Prevention of pneumoconiosis through periodic medical examination, workplace surveys, health education, isolation and enclosure of hazardous processes, dust control through wet drilling, and substitution of hazardous substances are being attempted.^3,4 Pneumoconiosis is a complex disorder with varied radiological manifestations which vary from person to person. It also depends on the duration and extent of exposure. The radiological findings are often confused with many other pulmonary diseases that show similar findings. Hence, how to conclude the diagnosis of pneumoconiosis and the validity of that conclusion is something to ponder. The ILO radiographs have been evolving from their genesis.⁵ However, it is not foolproof to stamp a case as pneumoconiosis. The classification has many strengths and pitfalls which need further introspection.

A policy for compensating the affected workers and their families has already been formulated in Rajasthan and is gradually being adopted by other states.³ Hence, pneumoconiosis is being taken seriously by the government and to decide the compensation, we need to diagnose pneumoconiosis. However, the ILO classification is not sufficient to diagnose a case as pneumoconiosis and it is not justified giving away a hefty compensation based on this diagnosis.

The pneumoconiosis has its classical lung findings, to mention a few, the snow-storm appearance of silicosis, holly leaf appearance of asbestosis, and ground-glass appearance of extrinsic allergic alveolitis.⁶ The diagnosis of pneumoconiosis based on the various chest radiographs needs expertise and training to ensure international comparability. Thus, ILO in collaboration with the National Institute for Occupational Safety and Health (NIOSH) came up with this international classification of radiographs to describe and record the various abnormalities of the chest on inhalation of dust systematically and to codify the various radiological abnormalities in a simple and reproducible manner.⁵ The previous edition of the classification was launched in 2011 and with some modifications the latest 2022 guidelines have come up.⁷ The codes have to be mastered and skills have to be acquired for one to be able to stamp the diagnosis of various pneumoconiosis.

However, there is still a lack of clarity in the uniformity of the coding, and there is a dearth of skilled physicians to interpret these codes. Can we say the ILO classification is variation-free and interpreted similarly by individual physicians in different settings and scenarios? A methodological review was conducted to unravel the strengths and pitfalls of ILO Classification (2022) for radiographic evaluation in Pneumoconiosis.

DESCRIPTION OF THE LATEST CLASSIFICATION GUIDELINES

The latest guidelines mention that the radiographs do not indicate pathological entities nor do they throw light on the working capacity or legal definition of pneumoconiosis.⁸ The cutoffs for providing compensation cannot be inferred from these radiographs. Furthermore, the radiographic features are not pathognomonic of dust exposure. The radiographs will be used for epidemiological research, screening, and surveillance. The basic principle is that there are a set of standard radiographs with text and footnotes and the subject radiographs are compared with the standard radiographs and coded according to the guidelines. Additional symbols are to be used to suggest any other additional pathology and also reader must use his clinical discretion to rule out the various differential diagnoses.^9-11

The technical quality of the radiographs is graded into good, acceptable with no technical defect, acceptable with minimal technical defect, and unacceptable, and based on this technical grading the radiographs are accepted or rejected. The radiographs are mainly assessed for parenchymal and pleural abnormalities.

As shown in Figure 1, the parenchymal abnormalities are mainly classified into small and large opacities. The small opacities are coded in terms of profusion, affected zones of the lung and shape and size. Profusion refers to the concentration of the small opacities in affected zones of the lung. The profusion is categorized into 4 categories and 12 subcategories based on standard calibrated radiographs. The degree of profusion increases as the category increases. The appropriate category is decided by comparing the subject radiograph with the standard radiograph. The central subcategory is the code mainly used if the reader is confident enough that the profusion belongs to that category. The other subcategories are used if an alternate category was seriously considered, for example, 2/1 indicates that the profusion was coded as category 2 after considering an alternate category 1. The affected zones are demarcated by horizontal lines drawn at one-thirds and two-thirds of the vertical distance between the lung apices and domes of the diaphragm. The two common shapes noted are- rounded and irregular. The rounded opacities sizes are coded as p, q, and r and the irregular ones as s, t, and u based on their diameters and widths. The code is written as two letters side by side. The more predominant shape and size is written first in the combination in case of mixed shapes and sizes, for example, pt, qt, and tq. If the opacities are of the same shapes and sizes, the same letter is written side by side, for example, pp, qq, and uu. The large opacities are categorized into A, B, and C where A being opacities not exceeding 50 mm, B exceeding 50 mm but not exceeding an equivalent area of the right upper zone, and C exceeding an equivalent area of the right upper zone.

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Figure 1:

International labor organization classification of radiographs. ILO: International labour organization, RUZ: Right upper zone.

Export to PPT

The pleural abnormalities are noted under 3 headings: pleural plaques, costophrenic angle obliteration, and diffuse pleural thickening. They are recorded separately for in-profile and face-on views and both the lungs. The plaques are coded in terms of site-like chest wall, diaphragm, para-spinal, para-cardiac, mediastinal spaces, calcification, and extent. The extent of the plaque is coded as 1, 2, and 3 based on the extent to which it covers the lateral chest wall from the apex to the costophrenic angle (CPA). The CPA obliteration is recorded in the presence or absence of diffuse pleural thickening and after ruling out scalloping of the diaphragm, muscle insertions, and ruling out a Morgagni or Bochdalek Hernia. The diffuse pleural thickening is also coded and its presence indicates a more restrictive functional impairment.

Apart from these, there are codes or symbols for additional pathologies encountered in the radiographs along with the reader’s comments. An abbreviated version of the classification is also used in certain scenarios where the codes are simplified to accomplish the classification quickly.

The ILO classification of radiographs is to be used mainly for research purposes and hence blinding of the radiographs is necessary to ensure the validity of the results. The recording will be done in a systematic and standardized manner with clerical help. The technical quality of the radiographs determines the reading rates, the prevalence of the abnormalities, the experience of the reader, and the purpose and length of the reading session. At least, two readers, preferably more, are required to classify the radiographs.

What’s new in the latest update? The innovation in the ILO classification includes digital chest radiographs.¹¹ This is a stepping stone that would simplify classifications soon which will not require the standard radiographs in physical form. The viewing principles for digital images have been strictly laid down in the guidelines which include:

• ILO images must be close enough (250 mm)

• The observer is seated comfortably

• The viewing surface should be clean and the intensity of illumination uniform

• The general illumination of the room should be low

• Subject and standard images should be displayed on medical-grade flat-panel monitors

• The diagonal display should be at least 54 cm per image

• The ratio of maximum to minimum luminance should be at least 50

• Pixel pitch ≤ 210 μm.

Furthermore, the digital images should be stored in adherence to the most recent version of Digital Imaging and Communications in Medicine. A computed or digital radiography is used as imaging equipment, and no exposure changes are to be done to the images as per the NIOSH guidelines. Quality assurance has to be done through periodic maintenance, optimization, and assessment. Standard measures to prevent unauthorized access to data should be employed to ensure confidentiality.

The revised edition incorporates a new set of digitally acquired standard images that replace the previous set. The basic principle of classification remains the same with modern technologies being infused into it.

The classification has its strengths and shortcomings. Pneumoconiosis diagnosis in a standardized and systematic manner is the need of the hour. Hence, to achieve that, the limitations of the classification have to be discussed, and the strengths have to be further improved. This would help achieve a system for diagnosing pneumoconiosis that is foolproof, standard, and without any variations.

STRENGTHS

This classification ensures universal comparability of the various radiographs of pneumoconiosis. The unique codes ensure the generalizability of reporting across nations. The quantification of the opacities in terms of shape, size, number, and area is possible. The classification also involves symbols for other pathologies and footnotes and comments which further help in coming to a differential diagnosis systematically. The newer innovation of using digital chest radiographs and the abbreviated classification helps reduce the time and the requirement of physical copies of the standard radiographs. The strict guidelines on viewing principles, image processing, and storing ensure the process’s quality control and make the diagnosis robust. Furthermore, blinding the readers to the worker’s occupational status helps reduce bias and ensures the validity of the findings. The password protection for storing images ensures confidentiality and abides by ethical principles. This classification is an instrumental tool in resource-poor low and middle income countries like India where advanced diagnostic tools are not so easily available or feasible. Hence, these standard radiographs serve as an important tool to classify pneumoconiosis and protect workers’ health.

LIMITATIONS

CONCLUSION

The need for digital ILO classification of radiographs is paramount in the field of occupational health. With the increasing prevalence of occupational lung diseases and the expanding use of digital radiography, adopting a standardized and efficient method for interpreting and classifying radiographic images has become essential. Digital ILO classification offers numerous advantages over traditional analog methods. First, it enables the digitization and storage of radiographic images, allowing easy access, retrieval, and data sharing. This facilitates remote consultations and second opinions and enhances research and epidemiological studies on occupational lung diseases. Digital classification also eliminates the need for physical storage space, reducing costs and the risk of image deterioration.

Furthermore, digital ILO classification improves the accuracy and consistency of radiographic interpretations. By employing standardized guidelines and criteria, it minimizes inter- and intra-observer variability, ensuring reliable and reproducible results. This is particularly crucial in the early detection and monitoring of occupational lung diseases, where prompt and accurate diagnoses can significantly impact treatment outcomes. In addition, digital classification systems can incorporate artificial intelligence (AI) algorithms aiding radiologists in image analysis and interpretation. AI-powered algorithms can assist in detecting subtle abnormalities, quantifying disease progression, and providing decision support, ultimately enhancing diagnostic accuracy and efficiency. Moreover, digital ILO classification promotes global harmonization and collaboration. With a standardized digital platform, radiologists and occupational health professionals from different regions and specialties can easily communicate, share expertise, and collectively contribute to research and knowledge sharing. This collaboration is vital in addressing the global burden of occupational lung diseases and developing effective preventive measures. However, it is essential to acknowledge and address potential challenges associated with digital ILO classification. Ensuring data privacy, implementing robust security measures, and addressing technical limitations are crucial aspects that need careful consideration.

In summary, adopting digital ILO classification of radiographs is necessary to overcome the limitations of analog methods and leverage the benefits of digital technologies. It improves accessibility, accuracy, consistency, and collaboration in radiographic interpretation, ultimately advancing occupational health and facilitating early detection and management of occupational lung diseases. As technology advances, further integration of AI and other innovative approaches holds promising potential for enhancing the efficiency and effectiveness of digital ILO classification in the future.