Interpreting Mortality Data
Cancer mortality statistics on this Web site are influenced by the accuracy of information on the death certificate. Cause of death determined by autopsy combined with clinical data is considered the best estimate of the true cause of death.1 Autopsy studies of mortality data coded according to the eighth or ninth revision of the International Classification of Diseases (ICD) (ICD-8A or ICD-9) indicate that, when neoplasms (cancers) are an underlying cause of death, the sensitivity of death certificates was 87%–93%, and their positive predictive value was 85%–96%.1 2 3 However, these studies are limited by selection bias, and less than 10% of deaths in the United States are autopsied.4
Death Certificates’ Reliability
The percentage of cancers coded as the underlying cause of death on the death certificate that agree with the cancer diagnosis in the medical record is an indication of the reliability with which the underlying cause of death can be determined from the death certificate. In a study by German et al., central cancer registry records from California, Colorado, and Idaho were linked with state vital statistics data and evaluated by demographic and tumor information across 79 site categories. A retrospective arm (confirmation rate per 100 deaths) compared death certificate data from 2002 to 2004 with cancer registry diagnoses from 1993 to 2004, while a prospective arm (detection rate per 100 deaths) compared cancer registry diagnoses from 1993 to 1995 with death certificate data from 1993 to 2004 by International Statistical Classification of Diseases and Related Health Problems (ICD) version used to code deaths. The overall confirmation rate for ICD-10 was 82.8% (95% confidence interval [CI], 82.6–83.0%), the overall detection rate for ICD-10 was 81.0% (95% CI, 80.4–81.6%), and the overall detection rate for ICD-9 was 85.0% (95% CI, 84.8–85.2%). These rates varied across primary sites, where some rates were <50%, some were 95% or greater, and notable differences between confirmation and detection rates were observed. For some of the most commonly diagnosed cancers in the U.S. (for example, prostate, breast, and lung and bronchus), confirmation or detection rates were 95% or greater. This study recorded important unique information on the quality of cancer mortality data obtained from death certificates, particularly underlying causes of death coded in ICD-10.5
Improving the Accuracy of Vital Statistics
CDC’s National Center for Health Statistics has worked with the Social Security Administration and the National Association for Public Health Statistics and Information Systems to develop and promote electronic systems to improve the accuracy and timeliness of vital statistics. Standard certificates for births and deaths were revised, and state vital registration systems are being re-engineered to collect data electronically. These systems will accommodate better certificate revisions, special studies or projects, and linkage with other health promotion programs. With regard to mortality data, handbooks have been revised for professionals who complete death certificates.
- Kircher T, Nelson J, Burdo H. The autopsy as a measure of accuracy of the death certificate. New England Journal of Medicine 1985;313(20):1263–1269.
- Engel LW, Strauchen JA, Chiazze L Jr, Heid M. Accuracy of death certification in an autopsied population with specific attention to malignant neoplasms and vascular diseases. American Journal of Epidemiology 1980;111(1):99–112.
- Schottenfeld D, Eaton M, Sommers SC, Alonso DR, Wilkinson C. The autopsy as a measure of accuracy of the death certificate. Bulletin of the New York Academy of Medicine 1982;58(9):778–794.
- Sinard JH. Factors affecting autopsy rates, autopsy request rates, and autopsy findings at a large academic medical center. Experimental and Molecular Pathology 2001;70(3):333–343.
- German RR, Fink AK, Heron M, Stewart SL, Johnson CJ, Finch JL, Yin D; the Accuracy of Cancer Mortality Study Group. The accuracy of cancer mortality statistics based on death certificates in the United States. Cancer Epidemiology 2011;35(2):126–131.