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National Hospital Discharge Survey (NHDS)

National Hospital Discharge Survey (NHDS) Session Overview NHDS: Overview Carol DeFrances, Ph.D. Analytic Issues Jean Kozak, Ph.D. Examples of Research Marni Hall, Ph.D. Accessing Data Maria Owings, Ph.D. New Directions Bob Pokras

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National Hospital Discharge Survey (NHDS)

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  1. National Hospital Discharge Survey(NHDS)

  2. Session Overview NHDS: Overview Carol DeFrances, Ph.D. Analytic Issues Jean Kozak, Ph.D. Examples of Research Marni Hall, Ph.D. Accessing Data Maria Owings, Ph.D. New Directions Bob Pokras

  3. Overview of the National Hospital Discharge Survey(NHDS) Carol DeFrances, Ph.D.

  4. NHDS Survey Years • Conducted annually 1965-present: • Latest data available: 2002 • 2003 will be available this Winter

  5. NHDS Survey Design • National probability sample: • Short stay non-Federal hospitals • Three stage design: 1. Geographic units 2. Hospital 3. Discharge

  6. More Information on NHDS Design and Operations • NCHS Publications: Series 1, No. 39 “Design and Operation of the National Hospital Discharge Survey: 1988 Redesign” http://www.cdc.gov/nchs/data/series/sr_01/sr01_039.pdf

  7. NHDS Sample Size • Hospitals: • About 500 hospitals sampled per year • Discharges: • Over 300,000 sampled per year

  8. NHDS Data Collection • Manual hospitals - 60% • Automated hospitals - 40%

  9. NHDS Manual Data Collection • NCHS – Statistical Design • Census Bureau – Field Work • Contractor – Coding and Data Entry

  10. NHDS Automated Data Collection • Electronic files obtained from: • States • Commercial firms • Individual hospitals

  11. NHDS Data Processing • NCHS: • Editing • Estimation

  12. NHDS Estimation • Weight: • Inverse of the probability of selection • Adjustments for non-response • Population weighting ratio adjustment

  13. Health Insurance Portability and Accountability Act (HIPAA)

  14. Variables onNHDS Public Use Data Files

  15. Patient Data • Age • Sex • Race • Expected source of payment • Discharge status • Marital status

  16. Hospital Characteristics • Geographic region • Bed size • Ownership

  17. Medical Data • Diagnoses and procedures • International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM)

  18. Additional Variables • Days of care • Month of discharge • DRG • Weight

  19. New Variables for NHDS Available beginning in the 2001 NHDS: - Source of Admission - Type of Admission

  20. National Survey of Ambulatory Surgery (NSAS) • Survey Years: Annually 1994-1996 • Collected data on ambulatory (outpatient) surgery in the U.S.

  21. NSAS Design • National probability sample • Short stay non-Federal hospitals (418) • Freestanding ambulatory surgery centers (333) • Sample size: • 120,000 sampled visits per year

  22. More Information on NSAS Design and Operations • Survey Design and Operations: NCHS Publications: Series 1, No. 37 “Plan and Operation of the National Survey of Ambulatory Surgery” http://www.cdc.gov/nchs/data/series/sr_01/sr01_037.pdf

  23. Additional Variables Collected for NSAS • Hospital vs. freestanding center • Type of anesthesia • Anesthesia provider

  24. Analytic Issues Lola Jean Kozak, Ph.D.

  25. Topics • Utilization measures • Medical coding system • Statistical issues

  26. NHDS provides data on hospitalizations not people

  27. Measures Include: • Discharges • Days of care • Average length of stay • Diagnoses • Surgeries/procedures

  28. Discharges • Include deaths • Include transfers to other hospitals or long-term care facilities • Do not usually include newborn infants

  29. Days of Care • Total number of days discharged patients spend in the hospital • All stays are counted as at least 1 day. • The admission day is counted, but not the discharge day • The number of days divided by the number of discharges is the average length of stay.

  30. Diagnoses • Disease, injury or other reason for hospitalization • Coded according to US adaptations of the International Classification of Diseases (ICD-9-CM)

  31. Diagnoses • Principal diagnosis: chiefly responsible for hospitalization • First-listed diagnosis: principal if specified, otherwise one listed first

  32. Diagnoses • All-listed: total number of times diagnoses appears on record • Any-listed: discharges with diagnosis in any position on record

  33. Hospital discharges with fractures, 2002 1,609,000 1,387,000 995,000 Principal or first listed Any listed All listed

  34. Surgery/Procedures • Surgical (appendectomy) • Diagnostic (spinal tap) • Therapeutic (chemotherapy) procedures • Coded according to US adaptations of the International Classification of Diseases

  35. NHDS provides data on inpatient procedures not total procedures

  36. Versions of the International Classification of Diseases • 8th revision used 1970-78 • 9th revision used 1979-2004 • 10th revision for use in future

  37. 8th Revision • Some codes different than in 9th Revision • Did not use E-codes • Made modifications in coding to accommodate available data

  38. 9th Revision • Addenda added annually since 1986 • Codes added, deleted, expanded, and revised • Lists of changes available in annual summary reports, file documentation

  39. Weights • Must use weighted data to obtain unbiased national estimates. • Each record has a weight • Sum the weights of the records

  40. Reliability • To be reliable, estimates must be based on at least 30 records . • And have a relative standard error of less than 30 percent. • Estimates based on 30-59 records should be used with caution.

  41. Standard Errors • Some standard errors are in Advance Data summaries • Generalized error curves are in the Series 13 Annual Summaries and data documentation • Use SUDAAN for specific standard errors - need access to confidential data

  42. Examples of Research Using the National Hospital Discharge Survey Marni Hall, Ph.D.

  43. 65 and over 45-64 All ages 15-44 Under 15 Average length of hospital stay by age, 1970-2001

  44. 65 and over 45-64 15-44 < 15 1970 1980 1990 2002 Percent distribution of hospital inpatients by age

  45. Hospital Transfers to Long Term Care Facilities in the 1990’s Jean Kozak Long-Term Care Interface – June 2002

  46. 2.8 Million 1.6 Million Transfers to long-term care,1990-1999 Number in Millions

  47. 12.8 days 8.3 days Average hospital stay for long-term transfers, 1990-1999

  48. Examples ofhealth services research: • Long-stay patients in short-stay hospitalsAcademyHealth Annual Meeting Presentation - Marni Hall and Maria Owings - June, 2003 • Admit source and type NAHDO Annual Meeting Presentation - Maria Owings and Marni Hall - December 2003 • Differences in length of stay in Veterans Health Administration and NHDS hospitalsMedical Care - GE Rosenthal et al. - August 2003

  49. Common NHDS Research Topics: • Deliveries • Type of birth, e.g. cesarean section • Obstetrical procedures • Length of stay

  50. U.S. Trends in Obstetric Procedures, 1990-2000 Jean Kozak and Julie Weeks Birth – September 2002

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