National Hospital Discharge Survey
The National Hospital Discharge Survey (NHDS) collects and produces national estimates on characteristics of inpatient stays in nonfederal, short-stay hospitals in the United States.
Hospitals are selected using a modified three-stage stratified design. Units selected at the first stage consist of either hospitals or geographic areas (primary sampling units (PSUs)). Hospitals within PSUs are selected at the second stage. Strata at this stage are defined by geographic region, PSU size, abstracting service status, and hospital specialty-size groups. Within these strata, hospitals are selected with probabilities proportional to their annual number of discharges. At the third stage, a random sample of discharges is selected. The NHDS hospital sample is updated every 3 years.
In 2006, 501 hospitals were selected; 478 were within scope, 438 participated (92%), and data were collected from medical records for approximately 376,000 discharges.
Annual modifications to the International Classification of Diseases, ninth revision, Clinical Modification (ICD-9-CM) may affect diagnosis and procedure categories. The NHDS was redesigned in 1988. Caution is required in comparing trend data from before and after the redesign.
National Center for Health Statistics. Health United States 2009: With Special Feature on Medical Technology. Hyattsville, Maryland. 2010; pp 467-468.