Methods and Limitations
We estimated the number of hospital discharges due to heart failure 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, non-federal 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 heart failure (ICD-9 codes 428) were estimated. Discharge rates were calculated using two population estimates as denominators: 1) the resident U.S.population from the Census, and 2) the number of U.S residents with diabetes obtained from the weighted sample of the civilian noninstitutionalized population in the National Health Interview Survey (NHIS). Discharge rates were age-adjusted on the basis of the 2000 U.S standard population. Estimates were presented by age, sex and race.
The number of hospitalizations involving persons with diabetes is underestimated because long-term and federal hospitals are not included in the NHDS sample. The number of race-specific discharges is particularly underestimated because a substantial proportion of discharges are missing racial classification and missing values for race are not imputed. 3
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.
- 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.
- DeFrances CJ, Lucas CA, Buie VC, Golosinskiy A. 2006 National Hospital Discharge Survey. National health statistics reports; no 5. Hyattsville, MD: National Center for Health Statistics. 2008.
- 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.