Usual interstitial pneumonia in asbestos-exposed cohorts - concurrent idiopathic pulmonary fibrosis or atypical asbestosis?

Our plain-English summary of Usual interstitial pneumonia in asbestos-exposed cohorts - concurrent idiopathic pulmonary fibrosis or atypical asbestosis?, by R.L. Attanoos, F.S. Alchami, F.D. Pooley, et al (Histopathology, 2016).

The study

• Authors: R.L. Attanoos, F.S. Alchami, F.D. Pooley, A.R. Gibbs
• Journal: Histopathology
• Published: 2016;69(3):492-8
• Cited by: 21 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Aims: To determine whether usual interstitial pneumonia (UIP) pattern fibrosis is seen in asbestosis.

Methods And Results: The occurrence of UIP pattern fibrosis was studied in four asbestos cohorts systematically referred following postmortem to the UK Pneumoconiosis Unit, Cardiff. The combined exposed workforce comprised >25 000 persons. Over the 17-year period, 233 subjects were identified; 210 had degrees of interstitial fibrosis with a fibrotic non-specific interstitial pneumonia pattern and subpleural accentuation, and three showed UIP pattern fibrosis. All three of these cases showed grade 4 fibrosis (honeycombing) with no asbestos fibre dose-response correlation. A Poisson distribution of probability analysis indicated that the observed cases of UIP in this workforce could be wholly accounted for by the prevalence of idiopathic pulmonary fibrosis (IPF) in the population.

Conclusions: UIP pattern fibrosis is rarely observed in asbestos-exposed subjects, and shows no dose-response correlation with asbestos fibres on mineral analysis; this points to an alternative disease, such as IPF. The results indicate that UIP pattern fibrosis should not be regarded as genuine asbestosis, irrespective of the status of asbestos biomarkers, and this impacts upon the postmortem handling of asbestos-related deaths.

© 2016 John Wiley & Sons Ltd.

In plain English

This study re-examined archived postmortem lung tissue from workers in four UK asbestos-exposed groups referred to the UK MRC Pneumoconiosis Unit: civilian Devonport dockyard workers, Cape Uxbridge asbestos board factory workers, gas mask factory workers and Cape Acre Mill textile workers. Two pathologists examined 1281 slides. Of 258 cases, 25 were excluded, leaving 233. A scarring pattern called usual interstitial pneumonia (UIP) was found in three workers (1.3%): two dockyard workers and one Cape Uxbridge worker. All three had advanced (grade 4) fibrosis. Their amphibole asbestos fibre counts were well below their cohort's median. Two counts fell below the cohort's 5th percentile and one below the 10th. One worker had 2.1 years of exposure and a working clinical diagnosis in life of cryptogenic fibrosing alveolitis. Another was a finance clerk rated as having low exposure. A probability calculation indicated that three cases in a workforce of 25,000 over 17 years could be explained as coinciding idiopathic pulmonary fibrosis. The authors concluded that asbestosis should not include UIP-pattern cases. They noted the study depended on how complete postmortem referrals were, was historical, and lacked full clinical follow-up and imaging.

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 pathology review of archived postmortem lung tissue slides from four UK asbestos-exposed cohorts, compared with earlier electron microscopic fibre counts, plus a Poisson probability analysis
• Who was studied: Workers from four UK asbestos-exposed cohorts (civilian Devonport dockyard, Cape Uxbridge asbestos board factory, gas mask factory in Nottingham, Cape Acre Mill textile plant) whose deaths were referred to the UK MRC Pneumoconiosis Unit. The combined workforce numbered more than 25,000 over a 17-year period. 258 cases were analysed and 233 were reviewed after exclusions.
• Exposure: Historical occupational asbestos exposure in dockyard, asbestos board (amosite insulation), gas mask and asbestos textile work, described as heavy. Retained amphibole asbestos fibres in lung tissue had been measured previously by transmission electron microscopy.
• Main results:
  • Of 258 cases analysed, 25 (10%) were excluded. Thirteen were excluded for concurrent pathology and nine for no lung fibrosis; organizing pneumonia was seen in three. 233 cases were reviewed.
  • UIP pattern fibrosis was found in three of the 233 reviewed workers (1.3%): two civilian dockyard workers and one Cape Uxbridge worker. None was found in the gas mask factory or textile plant workers.
  • All three UIP cases had grade 4 fibrosis but low amphibole asbestos fibre counts for their cohort. The two dockyard cases had counts of 23.2 and 36.7 against a cohort median of 123.3. The Cape Uxbridge case had 48 against a cohort median of 582. Two counts were below the cohort 5th percentile and one below the 10th.
  • In the Cape Uxbridge UIP case, the working clinical diagnosis in life was cryptogenic fibrosing alveolitis. Exposure lasted 2.1 years, the latent period was 38 years, and survival was under 4 years.
  • One dockyard UIP case was reported to be a finance clerk with a low occupational exposure rating.
  • Poisson calculations indicated that three idiopathic pulmonary fibrosis cases in a population of 25,000 over 17 years could be explained as coincidental. At an incidence of 6 per 100,000, the probability of one case arising in 25,000 people was more than 35%.
• The authors' conclusion: The authors concluded that UIP pattern fibrosis is rarely seen in asbestos-exposed subjects and shows no dose-response relation with asbestos fibres. They concluded it points to another disease, such as idiopathic pulmonary fibrosis, and that asbestosis should not include UIP-pattern cases whatever the asbestos biomarkers show.
• Limitations the authors state:
  • The study depended on how complete the postmortem referrals were, and was historical in nature.
  • There was no full clinical follow-up or imaging, such as consecutive high-resolution CT scans.
  • Judging the pattern of fibrosis in postmortem tissue can be highly problematic.
  • Agreement between pathologists (interobserver variation) was not tested.
  • Formal ferruginous/asbestos body counts were not performed.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Asbestosis.

Medical terms in this study, explained in our Lexicon: Interstitial, Idiopathic, Pulmonary Fibrosis, Fibrosis, Pneumoconiosis, Interstitial Fibrosis, Honeycombing, Dose-response relationship.

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