Methods and Limitations
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Methodology

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, 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)

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. 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. Rates were adjusted to the 2000 U.S. Standard Population using three age groups (0–64, 65–74, and 75+).

 

Limitations

The number of LEAs is underestimated because of the exclusion of long-term and federal hospitals from the NHDS sample and the omission of LEAs occurring in outpatient settings. Race-specific discharges are particularly underestimated because a substantial proportion of discharges are missing racial classification and missing values for race are not imputed. (2)

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. In 1983, the Center for Medicare and Medicaid Services 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. Kozak LJ. Underreporting of race in the National Hospital Discharge Survey.  Hyattsville, MD: National Center for Health Statistics. Advance data from Vital and Health Statistics, No. 265, 1995.