Healthcare Cost and Utilization Project-Nationwide Inpatient Sample
The Healthcare Cost and Utilization Project (HCUP) is a family of health care databases and related software tools developed through a federal-state-industry partnership to build a multistate health data system for health care research and decision making. The Nationwide Inpatient Sample (NIS), a component of HCUP, is the largest all-payer inpatient care database that is publicly available in the U.S. It contains data from 5 to 8 million hospital stays from about 1,000 hospitals sampled to approximate a 20% stratified sample of U.S. community hospitals.
The 2008 HCUP (NIS) approximates a 20% stratified sample of U.S. community hospitals (nonfederal, short-term, general, and other specialty hospitals, excluding hospital units of institutions). This universe of community hospitals is divided into strata using five hospital characteristics: ownership or control, bed size, teaching status, urban or rural location, and U.S. region. The NIS is a stratified probability sample of hospitals in the frame, with sampling probabilities proportional to the number of U.S. community hospitals in each strata. The frame is limited by the availability of inpatient data from the data sources currently participating in HCUP. The information abstracted from hospital discharge records is translated into a uniform format to facilitate both multistate and national-state comparisons and analyses.
The 2006 HCUP (NIS) contains data from approximately 8 million hospital stays from roughly 1,000 hospitals. The Inpatient Core file contains data for 100% of the discharges from a sample of hospitals in participating states.
Periodically, new data elements are added to the NIS and some are dropped. Although weights are produced to create estimates that approximate a nationally representative sample, because not all states provide data, some bias in national estimates may occur if omitted states have substantially different hospitalization patterns than states that provided data. The number of states in the HCUP (NIS) varies by year.
National Center for Health Statistics. Health United States 2009: With Special Feature on Medical Technology. Hyattsville, Maryland. 2010; pp 452-453.