Methods and Limitations
We estimated the number of hospital discharges for diabetic ketoacidosis (DKA) using data from the National Hospital Discharge Survey (NHDS), National Center for Health Statistics (NCHS), 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 patients' age, race, sex, length of stay, seven discharge diagnoses (one primary and six secondary diagnoses) and four surgical procedures. Methods used for conducting the survey have been described previously.(1,2)
DKA discharges were defined as discharges with DKA (ICD-9-CM code 250.1) as the first-listed diagnosis. Three-year averages were used to improve the precision of the annual estimates. Rates were calculated using estimates of the population with diabetes from the National Health Interview Survey and resident population estimate from the census.
Hospital discharge rates were age-adjusted using NCHS estimates of the 2000 U.S. population as the standard. Three age groups (0–44, 45–64, and 65+) were used for age-adjustment, with the exception of the detailed data tables by sex where two age groups were used (0–44 and 45+). Because the estimates were produced prior to the year 2000, a slight difference may occur between crude and age-adjusted rates for 2000.(3)
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 for diabetes-related diseases and procedures may not necessarily reflect rates per person; that is, persons who are hospitalized two or more times 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 Vital Health Statistics; 2000;1(39).
- Hall MJ, DeFrances CJ, Williams SN, Golosinskiy A, Schwartzman A. National Hospital Discharge Survey: 2007 summary. National Vital Health Statistics Reports 2010; 29.
- Klein RJ, Schoenborn CA. Age adjustment using the 2000 projected U.S. population. Healthy People Statistical Notes, no. 20. Hyattsville, Maryland: National Center for Health Statistics; 2001.
- 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.