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Patient Volume Database Source Information

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Database Source Overview

TDR Database Audit type Data source Facilities included Facilities excluded Size of audit**

Patient Trend Databases


(formerly the HIP, ER, HOP, POP)
Inpatient - (Diagnoses & Procedures) National Hospital Discharge Survey (NHDS)

Full documentation (pdf)
Short-stay hospitals (hospitals with an average length of stay for all patients of less than 30 days) or those whose specialty is general (medical or surgical) or children's general are included in the survey. Federal, military, and Veterans Administration hospitals 2010: 239 hospitals

A total of 151,551 patient records were used to the 2010 dataset.
Emergency Room (Diagnoses) National Hospital Ambulatory Medical Care Survey (NHAMCS)

Full documentation (pdf)
Hospitals with an average length of stay for all patients of less than 30 days (short-stay) or hospitals whose specialty was general (medical or surgical) or children's general were eligible. Federal hospitals, hospital units of institutions, and hospitals with less than six beds staffed for patient use. 2009: 412 Emergency Departments

A total of 34,942 patient records were used for the 2008 dataset.
Hospital Outpatient (Diagnoses) National Hospital Ambulatory Medical Care Survey (NHAMCS)

Full documentation (pdf)
Hospitals with an average length of stay for all patients of less than 30 days (short-stay) or hospitals whose specialty was general (medical or surgical) or children's general were eligible. Federal hospitals, hospital units of institutions, and hospitals with less than six beds staffed for patient use. 2009: 900 clinics within 220 outpatient departments

A total of 33,551 patient records were used for the 2008 dataset.
Physician Office (Diagnoses) National Ambulatory Medical Care Survey (NAMCS)

Full documentation (pdf)
-- Office-based, as defined by the AMA and AOA;

-- Principally engaged in patient care activities;

-- Nonfederally employed;

-- Not in specialties of anesthesiology, pathology, and radiology.
2010: 1,228 physicians responded with patient records.

A total of 31,229 patient records were used for the 2010 dataset.

NSAS

National Survey of Ambulatory Surgery (Procedures) National Survey of Ambulatory Surgery (NSAS)
Full documentation (pdf)
Ambulatory surgery procedures performed in short-stay hospitals and freestanding ambulatory surgery centers. Federal, military, and Department of Veteran’s Affairs hospitals. A total of 52,233 Patient records were used for the 2006 dataset.

** Numbers in this column are unweighted. However, data output in TDR's databases are weighted to estimate discharges for all U.S. facilities that correspond to the inclusion criteria.

How does the NHDS differ from the National Inpatient Sample published by HCUP?

The NIS uses a larger sample and is created by combining datasets from individual states.  However, not all U.S. states are represented in the sample.  For an in-depth comparison, see: Comparative Analysis of HCUP (NIS) and NHDS Inpatient Discharge Data.