Carbon monoxide-related injury estimation using ICD-coded data: methodologic implications for public health surveillance.

Estimates of unintentional deaths from carbon monoxide (CO) poisoning can be obtained from national mortality data. We explored ways of accurately estimating CO-related deaths from International Classification of Diseases, 9th Revision (ICD-9) coded U.S. mortality data. We evaluated and identified CO-related ICD-9 codes and created five classes of codes for case ascertainment that represented a continuum of the degree of certainty that the ICD-coded death was truly CO-related. We conducted single (underlying) cause-of-death and multiple-cause-of-death analysis using 20 years of data (1979-1998), and calculated sensitivity and positive predictive value using different criteria for case ascertainment. Single-cause analysis provided accurate estimates only when we used CO-exclusive E-codes, however this method failed to identify approximately one third of the CO-related deaths over the study period. Single-cause analysis overestimated the number of CO-related deaths when we used E-codes that were not exclusive to CO exposure. Identification of true CO-related deaths required multiple cause-of-death analysis and use of the CO nature-of-injury code, N986, to confirm suspected cases. Sensitivity of N986 was 99.5%, and positive predictive value of the individual E-codes in single cause-of-death analysis ranged from 1.5% to 92%. Estimating CO-related deaths from ICD-coded data requires a thorough understanding of the ICD codes, coding rules, and of the limitations imposed by case selection criteria and single cause-of-death analysis.

National vehicle emissions policies and practices and declining US carbon monoxide-related mortality.

CONTEXT: Carbon monoxide (CO) has been reported to contribute to more than 2000 poisoning deaths per year in the United States. OBJECTIVES: To evaluate the influence of national vehicle emissions policies and practices on CO-related mortality and to describe 31 years (1968-1998) of CO-related deaths in the United States. DESIGN AND SETTING: Longitudinal trend analysis using computerized death data from the Centers for Disease Control and Prevention, US Census Bureau population data, and annual CO emissions estimates for light-duty vehicles provided by the US Environmental Protection Agency. MAIN OUTCOME MEASURE: All deaths in the US for which non-fire-related CO poisoning was an underlying or contributing condition, classified by intent and mechanism of death. Negative binomial regression was used to incorporate every year of data into estimated percentage changes in CO emissions and mortality rates over time. RESULTS: During 1968-1998, CO-related mortality rates in the United States declined from 20.2 deaths to 8.8 deaths per 1 million person-years (an estimated decline of 57.8%; 95% confidence interval [CI], -62.4% to -52.6%). Following the introduction of the catalytic converter to automobiles in 1975, CO emissions from automobiles decreased by an estimated 76.3% of 1975 levels (95% CI, -82.0% to -70.4%) and unintentional motor vehicle-related CO death rates declined from 4.0 to 0.9 deaths per 1 million person-years (an estimated decline of 81.3%; 95% CI, -84.8% to -77.0%). Rates of motor vehicle-related CO suicides declined from 10.0 to 4.9 deaths per 1 million person-years (an estimated decline of 43.3%; 95% CI, -57.5% to -24.3%). During 1975-1996, an annual decrease of 10 g/mile of estimated CO emissions from automobiles was associated with a 21.3% decrease (95% CI, -24.2% to -18.4%) in the annual unintentional motor vehicle-related CO death rate and a 5.9% decrease (95%CI, -10.0% to -1.8%) in the annual rate of motor vehicle-related CO suicides. CONCLUSIONS: If rates of unintentional CO-related deaths had remained at pre-1975 levels, an estimated additional 11 700 motor vehicle-related CO poisoning deaths might have occurred by 1998. This decline in death rates appears to be a public health benefit associated with the enforcement of standards set by the 1970 Clean Air Act.

Surveillance for Asthma - United States, 1960-1995

This report summarizes and reviews national data for specific endpoints: self-reported asthma prevalence (1980-1994), asthma office visits (1975-1995), asthma emergency room visits (1992-1995), asthma hospitalizations (1979-1994), and asthma deaths (1960-1995).