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

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.