Asbestos-related diseases in mineworkers: a clinicopathological study

Our plain-English summary of Asbestos-related diseases in mineworkers: a clinicopathological study, by N. Ndlovu, D. Rees, J. Murray, et al (ERJ Open Research, 2017).

The study

• Authors: N. Ndlovu, D. Rees, J. Murray, N. Vorajee, G. Richards, J. teWaterNaude
• Journal: ERJ Open Research
• Published: 2017;3(3)
• Cited by: 6 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

The accurate diagnosis of asbestos-related diseases is important because of past and current asbestos exposures. This study evaluated the reliability of clinical diagnoses of asbestos-related diseases in former mineworkers using autopsies as the reference standard. Sensitivity, specificity, positive predictive value and negative predictive value were calculated. The 149 cases identified had clinical examinations 0.3-7.4 years before death. More asbestos-related diseases were diagnosed at autopsy rather than clinically: 77 versus 52 for asbestosis, 27 versus 14 for mesothelioma and 22 versus 3 for lung cancer. Sensitivity and specificity values for clinical diagnoses were 50.6% and 81.9% for asbestosis, 40.7% and 97.5% for mesothelioma, and 13.6% and 100.0% for lung cancer. False-negative diagnoses of asbestosis were more likely using radiographs of acceptable (versus good) quality and in cases with pulmonary tuberculosis at autopsy. The low sensitivity values are indicative of the high proportion of false-negative diagnoses. It is unlikely that these were the result of disease manifestation between the last clinical assessment and autopsy. Where clinical features suggest asbestos-related diseases but the chest radiograph is negative, more sophisticated imaging techniques or immunohistochemistry for asbestos-related cancers should be used. Autopsies are useful for the detection of previously undiagnosed and misdiagnosed asbestos-related diseases, and for monitoring clinical practice and delivery of compensation.

In plain English

This South African study compared diagnoses made during life with autopsy findings in 149 former asbestos mineworkers (131 male). All had been clinically examined by two asbestos compensation trusts and had autopsies at the National Institute for Occupational Health in 2010 and 2011. Most came from the Northern Cape Province, a former crocidolite mining area. Clinicians diagnosed 52 cases of asbestosis, 14 of mesothelioma and three of lung cancer. Autopsy found 77, 27 and 22. Of 126 asbestos-related diseases found at autopsy, 73 (57.9%) had not been diagnosed clinically. Sensitivity of the clinical diagnosis was 50.6% for asbestosis, 40.7% for mesothelioma and 13.6% for lung cancer. Specificity was 81.9%, 97.5% and 100.0%. Missed asbestosis was more likely with radiographs of acceptable rather than good quality, and when tuberculosis was found at autopsy. Most missed cancers were advanced at autopsy. The authors concluded that chest radiography, as the only imaging tool, substantially underdiagnoses these diseases but produces few false-positive results. They noted as a limitation that clinical examinations took place 0.3 to 7.4 years before death.

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: Retrospective, consecutive case series comparing clinical diagnoses with autopsy findings (autopsy as the reference standard)
• Who was studied: 149 former asbestos mineworkers (131, 87.9%, male; median age at death 66.1 years) in South Africa. All were clinically examined by the Asbestos Relief Trust and Kgalagadi Relief Trust and had autopsies at the National Institute for Occupational Health in 2010 and 2011.
• Exposure: Occupational asbestos mining exposure. Most (131, 87.9%) were from the Northern Cape Province, a former crocidolite mining area. First exposures occurred between 1952 and 1990 (median 1976). About one-third had also worked in other mining industries.
• Main results:
  • Clinical evaluation diagnosed 52 asbestosis cases, 14 mesothelioma cases and three lung cancer cases among the 149 mineworkers.
  • Autopsy diagnosed 77 (51.7%) cases of asbestosis, 27 (18.1%) cases of mesothelioma and 22 (14.8%) cases of lung cancer.
  • Of 126 asbestos-related diseases diagnosed at autopsy, 73 (57.9%) had not been diagnosed clinically.
  • Sensitivity and specificity of the clinical diagnoses were 50.6% and 81.9% for asbestosis, 40.7% and 97.5% for mesothelioma, and 13.6% and 100.0% for lung cancer.
  • Of 77 autopsy-diagnosed asbestosis cases, 38 (49.4%) had been missed clinically.
  • Compared with correctly diagnosed asbestosis cases, a missed asbestosis diagnosis was more likely with acceptable rather than good radiographs (odds ratio 12.33, 95% CI 2.54 to 59.72) and with pulmonary tuberculosis at autopsy (odds ratio 8.45, 95% CI 1.16 to 61.69).
  • Agreement between the severity of asbestosis on radiographs and at autopsy was poor (47.0%; kappa 0.15).
  • There were 35 missed cancers (16 mesotheliomas, 19 lung cancers). Most had advanced tumours at autopsy, and seven died while undergoing investigation.
• The authors' conclusion: The authors concluded that chest radiography, as the sole imaging tool in asbestos-exposed individuals, substantially underdiagnoses asbestos-related diseases but has good specificity, producing few false-positive results. They also concluded that autopsies are valuable for detecting undiagnosed disease, monitoring clinical practice and delivering compensation.
• Limitations the authors state:
  • There was an interval of 0.3 to 7.4 years between the last clinical assessment and death, during which disease, especially tumours, may have developed or progressed.
  • The number of cases was small for identifying factors linked to missed asbestosis diagnoses, so some factors may not have been identified.
  • Nonmalignant pleural diseases were not assessed, because for many cases the parietal pleurae were not submitted for autopsy.
  • The authors did not have the data to examine whether serial chest radiographs would improve accuracy.

Topics

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, Autopsy, Mesothelioma, Lung Cancer, Chest X-Ray, Immunohistochemistry.

Related studies

• Cape Plc: South African mineworkers' quest for justice — R. Meeran (2003)
• Compensation for environmental asbestos-related diseases in South Africa: a neglected issue — N. Ndlovu, J.T. Naude, et al. (2013)
• Malignant mesothelioma in south east England: clinicopathological experience of 272 cases — D.H. Yates, B. Corrin, et al. (1997)
• Malignant mesothelioma and occupational exposure to asbestos: a clinicopathological correlation of 1445 cases — V.L. Roggli, A. Sharma, et al. (2002)
• Pleomorphic epithelioid diffuse malignant pleural mesothelioma: a clinicopathological review and conceptual proposal to reclassify as biphasic or sarcomatoid mesothelioma — K. Kadota, K. Suzuki, et al. (2011)
• Synovial sarcoma of the pleura and its differentiation from other primary pleural tumours: a clinicopathological and immunohistochemical review of three cases — A.G. Nicholson, P. Goldstraw, et al. (1998)

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