Methods and Limitations
We estimated the number of hospital discharges involving nontraumatic lower extremity amputation (LEA) and diabetes using data from the National Hospital Discharge Survey (NHDS), National Center for Health Statistics, the 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 diagnoses (one primary and six secondary diagnoses), and four surgical procedures. Methods used for conducting the survey have been described previously.(1, 2)
Hospital discharges for which diabetes (ICD-9 code 250) was any listed diagnosis were used to examine discharges involving LEA. Cases were defined as discharges having diabetes as a listed diagnosis and an LEA procedure (ICD-9 procedure code of 84.1). Discharges with a traumatic amputation diagnosis code (ICD-9 diagnoses codes 895-897) were excluded. Rates were calculated using resident population estimates from the census and estimates of the population with diagnosed diabetes from the National Health Interview Survey. Rates were age-adjusted to the 2000 U.S. Standard Population using three age groups (0–64, 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.(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 more than once for the same condition may be counted more than once.
- Dennison C, Pokras R. Design and operation of the National Hospital Discharge Survey: 1988 redesign. National Vital and Health Statistics, 2000;1(39). Series 1, No. 39, 2000.
- Hall MJ, DeFrances CJ, Williams SN, Golosinskiy A, Schwartzman A. National Hospital Discharge Survey: 2007 summary. National health statistics reports; no 29. Hyattsville, MD: National Center for Health Statistics. 2010.
- Kozak LJ. Underreporting of race in the National Hospital Discharge Survey. National Vital and Health Statistics 1995;265.