Determining the Burden of Mesothelioma Mortality: An Investigation of Changes in Cause of Death Coding on the British Mesothelioma Register

Abstract

P-742 Introduction: The legacy of heavy past occupational asbestos exposures in Britain is a continuing increase in mesothelioma deaths today. The British mesothelioma register stands as one of the most comprehensive and consistent sources of mesothelioma mortality data for a given nation. It's strength lies in the fact that the criteria for including deaths have been consistently applied for over 35 years since the register was established in 1967. These criteria are based on textual information from death certificates and not on death coding to the International Classification of Disease (ICD) frameworks. In order to help inform meaningful comparisons of British mesothelioma mortality with that for other countries, the coding of the causes of death for mesothelioma register deaths was investigated and compared with national death data for Britain. Methods: Within the time period for each ICD revision, the ICD codes which were most frequently assigned to the underlying cause for those deaths included on the mesothelioma register were identified. The number of mesothelioma register deaths for these disease codes was then tabulated by year of death and sex. National death data for Britain for these same disease groups by year of death and sex was obtained from the Office for National Statistics for comparison. Results: For deaths included on the mesothelioma register prior to coding of cause of death to ICD 10 in 2001, the underlying cause of death was most frequently recorded as pleural cancer, lung cancer, cancer of unspecified site or peritoneal cancer. Prior to 1993 when medical enquiries to clarify causes of death were discontinued, these disease groups consistently accounted for around 55%, 15%, 15% and 5% of mesothelioma register deaths respectively. Around 90% of total pleural cancer deaths in Britain in this period are included on the mesothelioma register. Following the introduction of ICD 10 in 2001, around 95% of mesothelioma register deaths are now coded as mesothelioma (code C45) in the underlying cause. Conclusions: The data support the conclusion that prior to the coding of cause of death to ICD 10 in Britain, deaths recorded as cancer of the pleura do not adequately identify the totality of pleural mesothelioma deaths. Since the introduction of death coding to ICD10 in Britain, deaths coded to mesothelioma in the underlying cause closely match the inclusion criteria for the mesothelioma register.