Methods and Limitations
We estimated the number of hospital discharges due to ischemic heart disease among persons with diabetes using data from the National Hospital Discharge Survey (NHDS), National Center for Health Statistics, Centers for Disease Control and Prevention. NHDS collects data on hospital discharges from a sample of short-stay, nonfederal hospitals in the United States. Data collected include information on patients' age, race, sex, and length of stay, and on seven diagnoses (one primary and six secondary diagnoses) and four surgical procedures. Methods used for conducting the survey have been described previously.1, 2
Among discharges having diabetes (ICD-9 code 250) as a secondary diagnosis, discharges for which the first-listed diagnosis was ischemic heart disease (ICD-9 codes 410-414,429.2) were estimated. Rates were calculated using resident population estimates from the Census and estimates of the population with diabetes from the National Health Interview Survey.3 Rates were adjusted to the 2000 U.S. Standard Population using four age groups (0–44, 45–64, 65–74, and 75+).
Hospitalizations involving persons with diabetes are underestimated because long-term and federal hospitals are not included in the NHDS sample. Race-specific discharges are particularly underestimated because a substantial proportion of discharges are missing racial classification and missing values for race are not imputed.4
Because NHDS samples hospital discharges and not individual persons, NHDS hospital discharge rates may not necessarily reflect rates per person; that is, persons who are hospitalized more than once in a year may be counted more than once.
In 1983, Medicare instituted a prospective payment system that has influenced both hospitalization practices and disease reporting on discharge records.5
- Dennison C, Pokras R. Design and operation of the National Hospital Discharge Survey: 1988 redesign. Hyattsville, MD: National Center for Health Statistics. Vital and Health Statistics, Series 1, No. 39, 2000.
- Hall MJ, DeFrances CJ, Williams SN, Golosinskiy A, Schwartzman A. National Hospital Discharge Survey: 2007 summary [PDF-402KB]. National health statistics reports; no 29. Hyattsville, MD: National Center for Health Statistics. 2010.
- Botman SL, Moore TF, Moriarity CL, Parsons VL. Design and estimation for the National Health Interview Survey, 1995–2004 [PDF-299KB]. National Center for Health Statistics. Vital Health Stat 2000;2(130).
- Kozak LJ. Underreporting of race in the National Hospital Discharge Survey. Advance data from vital and health statistics, no. 265. Hyattsville, Maryland: National Center for Health Statistics, 1995.
- Panser LA, Naessens JM, Nobrega FT, Palumbo PJ, Ballard DJ. Utilization trends and risk factors for hospitalization in diabetes mellitus. Mayo Clin Proc. 1990 Sep;65(9):1171–1184.