Methods and Limitations
We estimated the number of hospital discharges involving lower extremity conditions among persons with diabetes by 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-CM code 250) as a listed diagnosis, peripheral arterial disease, ulcer/inflammation/infection, or neuropathy was identified with the following ICD-9-CM codes. People can have more than one lower extremity condition and any lower extremity condition was defined as having any of the three conditions. Analyses were conducted respectively for lower extremity conditions as first-listed diagnosis vs. any-listed diagnosis. Rates were calculated using estimates of the population with diabetes from National Health Interview Survey.3 Three-year averages were used to improve the precision of the annual estimates. Rates were adjusted to the 2000 U.S. Standard Population based on four age groups (0-44, 45-64, 65-74, and 75+).
|Peripheral Arterial Disease(PAD)||250.7, 440.2, 442.3, 443.8-443.9, 444.22|
|Ulcer/Inflammation/Infection||454, 707.1, 680. 6-680.7, 681.1, 682.6-682.7, 711.05-711.07, 730.05-730.07, 730.15-730.17, 730.25-730.27, 730.35-730.37, 730.85-730.87, 730.95-730.97, 785.4|
|Neuropathy||337.1, 357.2, 355, 358.1, 713.5, 094.0, 250.6|
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 the NHDS samples hospital discharges and not individual persons, discharge rates for diabetes-related diseases and procedures 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. Hyattsville, MD: National Center for Health Statistics No. 265, 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.