How Malignant Mesothelioma Was Coded in Mortality Data in Taiwan During Years When the Specific ICD Code Was Not Available?

Our plain-English summary of How Malignant Mesothelioma Was Coded in Mortality Data in Taiwan During Years When the Specific ICD Code Was Not Available?, by S.Y. Tai, J. Wu, L.J. Lee, et al (Clinical Epidemiology, 2021).

The study

• Authors: S.Y. Tai, J. Wu, L.J. Lee, T.H. Lu
• Journal: Clinical Epidemiology
• Published: 2021;13:1135-1140
• Cited by: 1 article, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Purpose: Malignant mesothelioma (MM) is associated with past exposure to asbestos and the latency period ranged from 20 to 40 years. Asbestos consumption reached a peak in the 1980s in Taiwan, and the MM mortality is expected to increase since 2000s. However, no specific code for MM was available before the International Classification of Disease, Tenth Revision (ICD-10), which was launched in 2008 in Taiwan. We examined how MM was coded in mortality data in Taiwan during the years when the ICD, Ninth Revision (ICD-9) was used.

Patients And Methods: Double-coded mortality data (each death coded according to both ICD-10 and ICD-9 codes) for the period 2002-2008 were obtained for analysis. Detection rates (similar to sensitivity) and confirmation rates (similar to positive predictive value) for various potential proxy ICD-9 codes for MM were calculated.

Results: For 113 deaths, for which the underlying cause of death was ICD-10 code C45 (MM), 14 corresponding ICD-9 codes were used. Four ICD-9 codes constituted 77% (87/113) of all MM deaths. The detection rate for code 199 (malignant neoplasm [MN] without specification of site) was 37% (42/113), that for code 163 (MN of pleura) was 18% (20/113), that for code 162 (MN of trachea, bronchus, and lung) was 12% (14/113), and that for code 173 (other MN of skin) was 10% (11/113). The confirmation rates for codes 199, 163, 162, and 173 were 0.9% (42/4759), 14.3% (20/140), 0.03% (14/51,778), and 1.5% (11/717), respectively.

Conclusion: ICD-9 codes 199, 163, 162, and 173 were most commonly used for MM deaths in Taiwan during the years before the ICD-10 introduction. However, when we used only ICD-9 code 163, which was most commonly used as a surrogate measure of MM in mortality studies during the ICD-9 era, we could detect only one-fifth of MM deaths in Taiwan.

© 2021 Tai et al.

In plain English

This short report examined how malignant mesothelioma deaths were coded in Taiwan under the ICD-9 system, which had no specific mesothelioma code. The authors used national death records for 2002 to 2008, in which each of 946,181 deaths was coded under both ICD-9 and ICD-10; ICD-10 has a mesothelioma code (C45). The 113 deaths coded C45 had received 14 different ICD-9 codes. Four covered 77% (87/113): code 199 (cancer without specified site) 37.2% (95% confidence interval 24.0 to 50.3), code 163 (cancer of the pleura) 17.7% (9.3 to 26.1), code 162 (trachea, bronchus and lung) 12.4% (5.5 to 19.3) and code 173 (other skin cancer) 9.7% (3.7 to 15.8). Of all deaths given code 163, 14.3% (20/140; 7.6 to 21.0) were coded C45 under ICD-10; for the other three codes it was 1.5% or lower. The authors suggested the skin coding may reflect the Chinese term for mesothelioma, literally "tumor between skins." They concluded that code 163 alone, widely used in earlier studies, detected only one-fifth of mesothelioma deaths. They noted that the ICD-10 reference likely undercounted true mesothelioma deaths. Asbestos exposure was not measured.

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: Short report; descriptive comparability (bridge coding) study of national double-coded mortality data. It calculated detection rates (similar to sensitivity) and confirmation rates (similar to positive predictive value) of ICD-9 codes for mesothelioma deaths, using ICD-10 code C45 as the reference.
• Who was studied: 946,181 deaths in Taiwan's double-coded mortality data, 2002 to 2008. Of these, 113 had ICD-10 code C45 (malignant mesothelioma) as the underlying cause of death.
• Exposure: Not studied. The study examined how death records were coded, not asbestos exposure, fiber types or jobs.
• Main results:
  • The 113 mesothelioma deaths (ICD-10 C45) received 14 different ICD-9 codes. Four codes (199, 163, 162 and 173) made up 77% (87/113).
  • Detection rates among the 113 C45 deaths (Table 1, with 95% confidence intervals): code 199 (malignant neoplasm without specification of site) 37.2% (24.0 to 50.3), 42/113. Code 163 (malignant neoplasm of pleura) 17.7% (9.3 to 26.1), 20/113.
  • Detection rates among the 113 C45 deaths (Table 1, with 95% confidence intervals): code 162 (trachea, bronchus, and lung) 12.4% (5.5 to 19.3), 14/113. Code 173 (other malignant neoplasm of skin) 9.7% (3.7 to 15.8), 11/113.
  • Confirmation rates are the share of all deaths given each ICD-9 code that had ICD-10 code C45 (Table 2, with 95% confidence intervals). Code 199: 0.9% (42/4759; 0.6 to 1.2). Code 163: 14.3% (20/140; 7.6 to 21.0). Code 162: 0.03% (14/51,778; 0.01 to 0.04). Code 173: 1.5% (11/717; 0.6 to 2.5).
  • For code 163, the confirmation rate was 15.3% (15/98) in men and 11.9% (5/42) in women.
  • For code 163 among men, the confirmation rate was highest at ages 45 to 54 (50.0%, 6/12; 95% confidence interval 1.0 to 99.0) and 55 to 64 (27.8%, 5/18; 0.3 to 55.3). These are based on small numbers.
  • For code 163 among women, the confirmation rate was highest at ages 65 to 74 (37.5%, 3/8).
  • The authors suggested that the Chinese term for mesothelioma, literally translated as "tumor between skins", may explain why 11 deaths were coded as other malignant neoplasm of skin (code 173).
• The authors' conclusion: The authors concluded that ICD-9 codes 199, 163, 162 and 173 were the codes most commonly used for mesothelioma deaths before ICD-10. They found that code 163 alone, the usual surrogate in earlier mortality studies, detected only one-fifth of mesothelioma deaths in Taiwan. They suggested using confirmation rates of multiple ICD-9 codes to estimate mesothelioma mortality more accurately before 2002 in Taiwan for future liability issues.
• Limitations the authors state:
  • Deaths coded ICD-10 C45 were used as the reference instead of pathological diagnoses or cancer registries. The authors state this underestimated the true number of mesothelioma deaths.
  • Caution is needed in applying these rates to years before 2002 because the number of deaths would be small.
  • Only three-character ICD-9 codes were used in Taiwan, so the more detailed four-character codes for 199 and 162 could not be used. The authors expected these would give higher confirmation rates.
  • Some coding errors came from misinterpretation of the Chinese diagnostic term, which would not occur in other countries.

Topics

Medical terms in this study, explained in our Lexicon: Malignant Mesothelioma, Latency, ICD-10 Code C45, Neoplasm, Pleura, Bronchus.

Related studies

• Impact of malignant mesothelioma in Taiwan: a 27-year review of population-based cancer registry data — L.J. Lee, Y.Y. Chang, et al. (2010)
• All-cause and cause specific mortality in a cohort of 20 000 construction workers; results from a 10 year follow up — V. Arndt, D. Rothenbacher, et al. (2004)
• Upcoming epidemic of asbestos-related malignant pleural mesothelioma in Taiwan: A prediction of incidence in the next 30 years — R.T. Lin, Y.Y. Chang, et al. (2019)
• Clustering of malignant pleural mesothelioma in asbestos factories: a subgroup analysis in a 29-year follow-up study to identify high-risk industries in Taiwan — L.J. Lee, C.K. Lin, et al. (2018)
• Based on available data, can we project an acceptable standard for industrial use of asbestos? No — A. Englund (1979)
• Based on available data, can we project an acceptable standard for industrial use of asbestos? Absolutely — K. Robock (1979)

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