Classification Change Affected Documentation of Mortality Rates
Studies conducted by the Centers for Disease Control (CDC) estimate that in the United States, at least 43,073 people have been killed by asbestos since 1979. However, they also state that this figure could account for as little as 20 percent of asbestos-related deaths.
The CDC’s assessment of mesothelioma mortality rates suggests that the number of nationwide asbestos-related deaths between 1979 and 2001 could be as high as 230,000 people. The significant difference between this figure and their original estimation is primarily attributed to the way the government classifies malignant mesothelioma deaths.
Prior to 1998, mesothelioma deaths were classified only as part of a group of asbestos cancers. Early death certificates only classified deaths by the location of the cancer instead of the cell types that composed a tumor. As a result, many mesothelioma cases were recorded simply as cancers of the pleura or peritoneum. Although the cancer was indicated in additional paperwork, the coding that is used to report deaths to statistics agencies only indicated the site of occurrence. Once the government assigned codes to the disease in 1999, the death rates nearly doubled.
With 935 fatalities recorded in 1998 and 2,343 noted in 1999, the CDC began to investigate the drastic increase. After reviewing the pleural and peritoneal cancer patients’ death certificates for any mention of mesothelioma, the CDC recalculated the registry records, creating a new proportion of total asbestos deaths that were estimated to be the disease. This more accurately reflected the number of fatalities that were the result of asbestos exposure before the 1999 coding switch.
Mesothelioma coding currently uses a system that identifies malignant neoplasms in the lining of the organs that may be affected. This helps differentiate between mesothelioma, which affects only the membrane around certain organs, and other cancers that attack the organs themselves. Pleural cancer is coded as ICD-9 code 163, peritoneal cancer is classified as ICD-9 code 158 and pericardial cancer is referred to as ICD-9 code 164.