Acute coronary syndrome national statistics: challenges in definitions.
BACKGROUND
Increasing convergence in the management of acute myocardial infarction (AMI) and unstable angina (UA) has led some to consider whether these 2 diagnoses should be consolidated into acute coronary syndrome (ACS) for the purpose of coronary heart disease surveillance.


METHODS
We used the 1988-2001 Nationwide Inpatient Sample, which has demographic and diagnosis data on 6 to 7 million discharges per year from a sample of US nonfederal hospitals. We identified discharges with a first- or all-listed diagnosis of AMI ( International Classification of Diseases, Ninth Revision, Clinical Modification 410) or UA (International Classification of Diseases, Ninth Revision, Clinical Modification 411) and defined ACS-first as a primary diagnosis of either condition and all-listed ACS as codes 410 or 411 among any diagnoses. Sampling weights were applied to produce yearly national discharge estimates; annual population estimates were used to calculate yearly hospital discharge rates; rates were then adjusted to the 2000 standard population.


RESULTS
Rates of first- and all-listed AMIs changed little. Rates of first-listed UA fell 87% from 29.7/10,000 in 1988 to 3.9/10,000 in 2001. This sharp decline was seen among all age and sex groups. Consequently, rates of ACS as a primary diagnosis declined 44%. In contrast, discharge rates for all-listed UA and ACS declined only modestly.


CONCLUSIONS
As a primary diagnosis, UA is disappearing. Rates of first-listed ACS are quite sensitive to the decline in UA. Although discharge data based on first-listed diagnoses have been used to estimate the national incidence of AMI, they may not provide accurate data regarding current trends for ACS.
Department of Public Health Sciences, Wake Forest University School of Medicine, Winston-Salem, NC, USA. abertoni@wfubmc.edu
Alain G
AG
Bertoni
Denise E
DE
Bonds
Thomas
T
Thom
G John
GJ
Chen
David C
DC
Goff
D000208:Acute Disease; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000789:Angina, Unstable / Q000175:diagnosis / Q000453:epidemiology*; D006801:Humans; D008875:Middle Aged; D009203:Myocardial Infarction / Q000175:diagnosis / Q000453:epidemiology*; D010351:Patient Discharge; D013577:Syndrome