National Hospital Discharge Survey (NHDS) and National Survey of Ambulatory Surgery (NSAS)

1. National Hospital Discharge Survey (NHDS) and National Survey of Ambulatory Surgery (NSAS) 2006 Data Users Conference July 10, 2006 3:30pm-5:00pm Session #15

2. Session Overview NHDS: Overview Carol DeFrances, PhD Analytic Issues Karen Lees, MPH Examples of Research Jean Kozak, PhD Accessing Data Marni Hall, PhD New Directions Bob Pokras, MA

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

4. NHDS Survey Years • Conducted annually 1965-present • Latest data available: 2004 • 2005 will be available this Winter

5. NHDS Survey Design • Scope and coverage: • Short stay, non-Federal hospitals • ALOS < 30 days • General and children’s general hospitals

6. NHDS Sampling Plan • Three stage design: • Geographic units • Hospital • Discharge

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

8. NHDS Data Collection • Manual hospitals - 56% • Automated hospitals - 44% • Overall response rate for the 2004 NHDS – 92%

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. Variables onNHDS Public Use Data Files

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

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

16. Medical Data • International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM) • Diagnoses (up to 7) • Procedures (up to 4)

17. Additional Variables • Days of care • Month of discharge • Diagnoses Related Group (DRG) • Weight

18. New Variables for NHDS • Available beginning in the 2001 NHDS: • Source of Admission • Type of Admission

19. New Variables for the NHDS • Beginning to collect with the 2007 NHDS: • Admitting Diagnosis • Present on Admission checkbox for all seven diagnoses collected

20. Analytic Issues Karen Lees, MPH

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

22. NHDS provides data on hospitalizations not people

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

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

25. 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

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

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

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

29. Hospital discharges with fractures, 2004 Source: CDC/NCHS, National Hospital Discharge Survey (NHDS)

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

31. NHDS provides data on inpatient procedures not total procedures

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

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

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

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

36. 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

37. 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

38. Examples of Research Jean Kozak, Ph.D.

39. Percent distribution of discharges and days of care by age, 2004 Days of care Discharges 85 and over 75-84 65-74 55-64 Age in years 45-54 35-44 25-34 15-24 5-14 0-4 0 20 10 10 20 Percent distribution Source: CDC/NCHS, National Hospital Discharge Survey (NHDS)

40. Average length of hospital stay by age, 1980-2004 Source: CDC/NCHS, National Hospital Discharge Survey (NHDS)

41. Percent of hospital inpatients transferred to long-term care facilities, by age, 1990-2004 Source: CDC/NCHS, National Hospital Discharge Survey (NHDS)

42. Hospitalization rates for major diagnostic categories by sex, 2004 Males Females Source: CDC/NCHS, National Hospital Discharge Survey (NHDS)

43. Percent distribution of patients hospitalized for heart disease, 2003 All other diagnoses 87% Source: CDC/NCHS, National Hospital Discharge Survey (NHDS)

44. Hospitalization rate for cancer,1990-2004 1990 63.0 2004 41.2 Source: CDC/NCHS, National Hospital Discharge Survey (NHDS)

45. Number of discharges with HIV diagnoses by age, 1995, 2000 and 2004 Source: CDC/NCHS, National Hospital Discharge Survey (NHDS)

46. Hospitalization rates for depression for boys and girls 5-19 years of age, 1990-92 and 2002-04 Source: CDC/NCHS, National Hospital Discharge Survey (NHDS)

47. Hospitalization rates for inpatients with Clostridium difficile by age, 1996-2003 Source: McDonald LC, et al. Emerg Infect Dis. 2006;12(3): 410-5.

48. Hospitalization rates for avoidable conditions by race, patients under 65 years of age, 1990-2004 Black patients White patients Source: CDC/NCHS, National Hospital Discharge Survey (NHDS)

49. Average length of stay for selected diagnostic categories, 2004 Source: CDC/NCHS, National Hospital Discharge Survey (NHDS)

50. Average length of stay for hip fractures, 1990-2004 12.8 days 1990 6.4 days 2004 Source: CDC/NCHS, National Hospital Discharge Survey (NHDS)