Comparison of Two Information Sources for Cause-of-Death Follow-up in the Russian Federation: The Asbest Chrysotile Cohort Study

Our plain-English summary of Comparison of Two Information Sources for Cause-of-Death Follow-up in the Russian Federation: The Asbest Chrysotile Cohort Study, by J. Schüz, E. Kovalevskiy, M. Moissonnier, et al (Methods of Information in Medicine, 2020).

The study

• Authors: J. Schüz, E. Kovalevskiy, M. Moissonnier, A. Olsson, D. Hashim, H. Kromhout, S. Kashanskiy, O. Chernov, I. Bukhtiyarov, E. Ostroumova
• Journal: Methods of Information in Medicine
• Published: 2020;59(1):9-17
• Cited by: 4 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: The Asbest chrysotile cohort was set up in Asbest town, Sverdlovsk oblast, Russian Federation, among the current and former workforce of the world's largest operating chrysotile mine and its processing mills, to investigate cancer risk in relation to occupational exposure to chrysotile.

Objectives: The cohort of 35,837 people was followed-up for mortality using cause-of-death information from official death certificates issued by the Civil Act Registration Office (ZAGS) of Sverdlovsk oblast from 1976 to 2015. Data were also retrieved from the electronic cause-of-death registry of the Medical Information Analytical Centre (MIAC) of Sverdlovsk oblast, which was launched in 1990 and operates independently of ZAGS. The objectives were to compare the completeness of record linkage (RL) with ZAGS and with MIAC, and to compare the agreement of cause-of-death information obtained from ZAGS and from MIAC, with a focus on malignant neoplasms.

Methods: RL completeness of identifying cohort members in ZAGS and in MIAC was compared for the period 1990 to 2015. In the next step, for the comparison of the retrieved cause-of-death information, 5,463 deaths (1,009 from cancer) were used that were registered in 2002 to 2015, when causes of death were coded using International Statistical Classification of Diseases and Related Health Problems, 10th revision (ICD-10) nomenclature by MIAC. For ZAGS, original cause-of-death text from the death certificates was obtained and then coded according to ICD-10 by the International Agency for Research on Cancer/World Health Organization (IARC/WHO). Agreement was evaluated at various levels of detail, and reasons for any disagreements between the MIAC and the IARC/WHO ICD-10-coded cancer diagnosis were systematically explored.

Results: A total of 10,886 deaths were obtained from all avenues of follow-up for the period 1990 to 2015 in the cohort; 10,816 (99.4%) of these were found in ZAGS. This percentage was 88.3% if only automated deterministic RL was used and 99.4% when deterministic RL was complemented with manual searches of cohort members. Comparison of the cause-of-death information showed agreement of 97.9% at the ICD-10 main group level between ZAGS (coded by IARC/WHO) and MIAC. Of 1,009 cancer deaths, 679 (67.3%) cases had identical coding, 258 (25.6%) cases corresponded at the three-character ICD-10 level, 36 (3.6%) had codes that were within the same anatomical or morphological cluster, and for only 36 (3.6%) cases were major discrepancies identified. Altogether, the agreement between IARC/WHO coding of cause-of-death information from ZAGS and MIAC coding of malignant neoplasms was therefore 96.4%.

Conclusions: RL completeness and agreement of cause-of-death information obtained from ZAGS and from MIAC were both very high. This is reassuring for the quality of cancer mortality follow-up of the Asbest chrysotile cohort. For future epidemiological studies in the Russian Federation, ZAGS appears to be a reliable information source for mortality follow-up, if the automated RL is complemented with manual searches of cohort members. MIAC is a good resource for prospective studies.

The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial-License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes, or adapted, remixed, transformed or built upon. (https://creativecommons.org/licenses/by-nc-nd/4.0/).

In plain English

This study checked death tracking in the Asbest chrysotile cohort. The cohort is 35,837 people who worked at least 1 year between 1975 and 2010 in a chrysotile mine and mills in Asbest, Sverdlovsk oblast, Russian Federation. The paper did not report cancer risks. It compared two death-record sources: the Civil Act Registration Office (ZAGS) and the Medical Information Analytical Centre (MIAC). There were 10,886 cohort deaths from 1990 to May 2015. Automated matching found 88.3% of them in ZAGS, manual searches raised this to 10,816 (99.4%), and 70 were never found in ZAGS. All eight mesothelioma deaths in the search window were found in both sources. For 5,463 deaths in 2002 to 2015, the sources agreed on the broad cause-of-death group for 97.9%. For 1,009 cancer deaths, coding agreed fully or partly for 96.4%, with 36 major discrepancies. The authors concluded that ZAGS appears reliable for future Russian studies if automated matching is supplemented by manual searches or if ZAGS adopts stochastic record linkage. They noted that no comparison data existed before 1990, and coding was compared only from 2002.

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: Methods and validation study within a retrospective cohort. It compared the completeness of record linkage and the agreement of cause-of-death coding between two independent death registries. It is not an analysis of cancer risk.
• Who was studied: The Asbest chrysotile cohort: 35,837 people who worked at least 1 year in the mine or processing mills in Asbest, Sverdlovsk oblast, Russian Federation, between 1975 and 2010. Mortality follow-up ran from 1976 to 2015. Linkage was compared for deaths in 1990 to May 2015, and cause-of-death coding for 5,463 deaths in 2002 to 2015.
• Exposure: The cohort was set up because of work at a chrysotile mine and its processing mills. This paper did not analyze exposure; it evaluated sources of death records.
• Main results:
  • From all sources, there were 10,886 cohort deaths from January 1990 to May 2015. ZAGS found 10,816 (99.4%) of them: 9,613 through automated deterministic record linkage and 1,203 through manual searches. Automated linkage alone gave 88.3% completeness. 70 deaths found in other sources were not found in ZAGS.
  • Among 9,979 deaths found either by automated ZAGS linkage or in MIAC, 96.3% were found in ZAGS and 93.7% in MIAC. MIAC completeness rose to 95.0% when 2009, a year with known under-recording, was excluded.
  • There were 544 lung cancer deaths. Automated linkage found 526 (96.7%) of them in ZAGS, and manual searches found the remaining 18. All eight mesothelioma deaths in the search window were found in both ZAGS and MIAC.
  • For 5,463 deaths in 2002 to 2015, ZAGS-based (IARC/WHO-coded) and MIAC-coded causes of death agreed at the ICD-10 main group level for 97.9% (5,349 of 5,463).
  • For 1,009 cancer deaths, 679 (67.3%) matched at the four-character ICD-10 level. Another 258 (25.6%) matched at the three-character level, and 36 (3.6%) fell within the same anatomical or morphological cluster. Overall agreement was 96.4%.
  • 36 cancer deaths (3.6%) had major discrepancies. In 19 of them, one source coded the death as cancer and the other did not. The remaining 17 were judged to be coding errors in the MIAC registry, including one pleural mesothelioma coded as cancer of the pleura.
• The authors' conclusion: The authors concluded that the very high record linkage completeness indicates good-quality cancer mortality follow-up for the cohort. They judged that ZAGS appears to be a reliable source for future Russian studies if automated linkage is complemented with manual searches or if ZAGS implements stochastic record linkage. They also said MIAC must further improve its completeness before becoming a major source.
• Limitations the authors state:
  • MIAC covers only the period from 1990, so there were no comparison data for 1976 to 1990.
  • Accuracy of cause-of-death coding could be compared only for deaths from 2002 onward.
  • The approach could not precisely quantify the cohort's overall follow-up completeness, and more deaths may have been missed in earlier years.
  • As in all death-certificate studies, it is unknown how well the recorded underlying cause matches the true cause of death.

Topics

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

Medical terms in this study, explained in our Lexicon: Chrysotile, Cohort Study, Occupational Exposure, Death Certificate, Neoplasm, IARC.

Related studies

• Occupational cohort study of current and former workers exposed to chrysotile in mine and processing facilities in Asbest, the Russian Federation: Cohort profile of the Asbest Chrysotile Cohort study — J. Schüz, I. Bukhtiyarov, et al. (2020)
• Cancer mortality in chrysotile miners and millers, Russian Federation: main results (Asbest Chrysotile Cohort-Study) — J. Schüz, E. Kovalevskiy, et al. (2024)
• Tobacco smoking among chrysotile asbestos workers in Asbest in the Russian Federation — A. Olsson, E.V. Kovalevskiy, et al. (2020)
• A comparison of parallel dust and fibre measurements of airborne chrysotile asbestos in a large mine and processing factories in the Russian Federation — E. Feletto, S.J. Schonfeld, et al. (2017)
• A retrospective cohort study of cancer mortality in employees of a Russian chrysotile asbestos mine and mills: study rationale and key features — J. Schüz, S.J. Schonfeld, et al. (2013)
• Developing a company-specific job exposure matrix for the Asbest Chrysotile Cohort Study — E. Feletto, E.V. Kovalevskiy, et al. (2022)

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