Methods and Limitations
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Methodology

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, 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 about patients' age, race, sex, and length of stay, and for seven 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 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 resident population estimates and estimates of the population with diabetes from National Health Interview Survey. Rates were adjusted to the 2000 U.S. Standard Population using three age groups (0–44, 45–64, and 65+), except for the detailed data tables by sex where two age groups were used (0–44 and 45+) for age-adjustment.

Hospital discharge rate estimates were age-adjusted using "National Center for Health Statistics" estimates of the 2000 U.S. population as the standard. Because the estimates were produced prior to the year 2000, a slight difference may occur between crude and age-adjusted rates for 2000.(3)
 

Data Limitations

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. (3)

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.

In 1983, Medicare instituted a prospective payment system that has influenced both hospitalization practices and disease reporting on discharge records.
 

References

  1. 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.
  2. Graves EJ. National Hospital Discharge Survey: Annual Summary, 1990. Hyattsville, MD: National Center for Health Statistics. Vital and Health Statistics, Series 13, No. 112, 1992.
  3. 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. January 2001.
  4. 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.