National Hospital Discharge Survey (NHDS)

1. National Hospital Discharge Survey(NHDS) National Survey of Ambulatory Surgery (NSAS) Centers for Disease Control and Prevention

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

4. National Health Care Surveys • Visits to • Doctors’ offices (NAMCS) • Emergency rooms (NHAMCS) • Outpatient departments (NHAMCS) • Inpatients (NHDS) • Ambulatory surgery (NSAS) (1994-96) • Long term care • Nursing homes (NNHS) • Home health care (NHHCS) • Hospices (NHHCS)

5. Handout Internet Resources: Hospital Discharge and Ambulatory Surgery Data For an email of this table of hotlinks, write to: NHDS@cdc.gov

8. Survey Years • NHDS: Annually 1965-present • Latest data available – 2000 • 2001 will be available this Winter • NSAS: Annually 1994-1996

9. Survey Design and Operations • NCHS Publications • NSAS – Series 1 No. 37 • NHDS – Series 1 No. 39

12. Survey Design • Similar designs and methods • National probability samples • Short stay non-Federal hospitals (NHDS/NSAS) • Freestanding ambulatory surgery centers (NSAS)

13. Survey Design • Three stage design • PSU • Facility • Discharge/visit

14. Facility Sample Size • 525 NHDS hospitals • 751 NSAS facilities • 418 Hospitals • 333 Freestanding surgery centers

15. Response Rates • NHDS – over 90 percent 300,000 sampled discharges per year • NSAS -- 80 percent for hospitals -- 70 percent for FSASC 120,000 sampled visits per year

16. Data Collection • NHDS • Manual; 60% • Automated; 40% • NSAS • All manual

17. Manual Data Collection • NCHS – Statistical Design • Census Bureau – Field Work • ASI – Coding and Data Entry

18. Automated Data Collection • Purchase files • States • Commercial firms • Individual hospitals

19. Data Collection • NCHS • Editing • Estimation

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

21. Variables on Public Use Data Files

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

25. Facility Characteristics • Geographic region • Bed size (NHDS) • Ownership (NHDS) • Hospital vs. Freestanding (NSAS)

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

27. Additional Variables • NHDS • Days of care • Month of admission/discharge • DRG • NSAS • Month of visit • Type of anesthesia • Anesthesia provider • WEIGHT

28. New Variables for NHDS • Available for Year 2001 NHDS • Source of Admission • Type of Admission

29. Source of Admission • Physician Referral • Clinical Referral • HMO Referral • Transfer from a Hospital • Transfer from Skilled Nursing Facility • Transfer from other health facility • Emergency Room • Court/Law Enforcement • Other • Not Available

30. Type of Admission • Emergent • Urgent • Elective • Newborn • Not available/unknown

32. Summary • Source of the data • Design • Methods • Variables

33. Analytic Issues(things you need to know about NHDS data) Lola Jean Kozak, Ph.D.

34. Topics • Utilization measures • Populations • Medical coding system • Statistical issues

35. NHDS Provides Data on Hospitalizations Not People

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

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

38. 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

39. Average Length of Stay • Calculated by dividing the number of days of care by the number of discharges • May want to examine length of stay distributions

40. Length of stay for women with deliveries: 1995 and 2000 Discharges in thousands

41. Diagnoses • Disease, injury or other reason for hospitalization • Coded according to US adaptations of the International Classification of Diseases

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

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

44. Hospital discharges with fractures, 2000 1,542,000 1,226,000 982,000 Principal or first listed All listed Any listed

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

46. NHDS Provides Data on Inpatient Procedures Not Total Procedures

47. Procedures mainly performed in inpatient settings, 1996 Appendectomy Coronary artery bypass graft Hysterectomy Cesarean section Number in thousands

48. Procedures mainly performed in ambulatory settings, 1996 Arthroscopy Of knee D & C Endoscopy of large intestine Insertion of lens Number in thousands

49. Population for Rates • Mid-year population estimates from the U.S. Bureau of the Census • Civilian resident population • Adjustments for underenumeration

50. Versions of the International Classification of Diseases • 8th revision used 1970-78 • 9th revision used 1979-2002 • 10th revision for use in future