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					Overview of the NAMCS
    and NHAMCS


Linda McCaig and David Woodwell

   2008 NCHS Data Users Conference
           August 12, 2008
               Overview
•   Background
•   Data uses
•   Survey methodology
•   Current and proposed survey items
•   User considerations
•   Methodological studies
•   Data dissemination
•   NCHS Research Data Center

                                        2
National probability sample
          surveys
• National Ambulatory Medical Care
  Survey (NAMCS)
  – Patient visits to non-federal office-
    based physicians
• National Hospital Ambulatory
  Medical Care Survey (NHAMCS)
  – Patient visits to EDs and OPDs of non-
    federal short-stay hospitals
                                             3
Original NAMCS survey goals

 •   National statistics
 •   Professional education
 •   Health policy formulation
 •   Quality assurance



                                 4
        NAMCS history

• Survey began in 1973
• Annual data collection through
  1981 (NORC)
• Conducted in 1985 (NORC)
• Annual began again in 1989
  (Census)

                                   5
         NHAMCS history
• Survey began in 1992
• Annual data collection (Census)




                                    6
 How are NAMCS and NHAMCS
          data used?
• Changes in utilization and practice
  – diagnoses, tests/procedures, prescribing

• Quality of care
  – Impact of performance measures and
    educational campaigns
  – Healthy People 2010 objectives
• Health disparities
• Adoption/Diffusion of new technologies
                                               7
8
           Data users

• Medical associations
• Government agencies
• Institute of Medicine
• Health services researchers
• University and medical schools
• Broadcast and print media
                                   9
10
The IOM report




                 11
 Trends in emergency department visits, number of hospitals, and
number of emergency departments in the United States, 1994-2004




                     Kellermann A. N Engl J Med 2006;355:1300-1303
                                                                     12
                                   Number of patients arriving (line) and
                                occupancy (bars) of EDs by hour of day and
                                            admission status
                                      60,000
Average daily number of ED patients




                                      50,000


                                      40,000


                                      30,000


                                      20,000


                                      10,000


                                          0
                                               0   1   2   3     4   5   6   7    8   9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
                                                                                 Hour of day on 24-hour clock

                                                               Transferred or died      Admitted      Discharged   Arrival rate




                                                                                                                                    13
Average annual numbers of emergency department visits
  and hospital readmissions within 7 days of a hospital
discharge in relation to the number of hospital discharges
    with corresponding ratios: United States, 2005-06

                                                1
            Hospitalreadmissions
            Hospital readmission                                       719,000
                                                                                       21
            Emergency department visits
           Emergency department visits                            2,321,000
                                                                                       68



                                                       34,019,000

          Hospital inpatientdischarges
           Hospital inpatient discharges                                            1000




  Note: 1Hospital readmissions include admission to the same hospital as the emergency department visit or transfer to another hospital.
  Example of use: For every 1,000 hospital inpatient discharges, there were 68 emergency department visits, and 21 hospital readmissions.14
Percentage of ED visits at which an opioid
was prescribed by pain severity and race

                                                             White        Other race
                     60
                     50
 Percent of visits




                     40
                     30
                     20
                     10
                     0
                                M



                                           M



                                                        Se




                                                                                           M



                                                                                                  M



                                                                                                              Se
                                 ild



                                             od




                                                                                           ild



                                                                                                   od
                                                           ve




                                                                                                                 ve
                                               er




                                                                                                     er
                                                              re




                                                                                                                    re
                                                 at




                                                                                                       at
                                                    e




                                                                                                          e
                                         1997-2000                                               2003-2005
                          NOTE: Pain severity was not collected in 2001-2002.                                       15
                          SOURCE: Wilper AP et al. Health Affairs. 2008;Jan-Feb:w84-w93.
Ambulatory care visit rates by setting

                                                             1996       2006

                           200
                                     171   179



                           150
 Visits per 100 persons




                           100
                                                                              67
                                                   57       60       54
                            50                                                               35            41
                                                                                                     34
                                                                                       26


                             0
                                 Primary care       Surgical      Medical specialty    Outpatient   Emergency
                                    office       specialty office     office*         department*   department*

                          *p<0.05.                                                                                16
  Ambulatory care antimicrobial
prescribing rates for HP2010 goals

                                                       Common cold                 Otitis media <5YO

                                   3000                                                                              80
  Prescriptions per 100,000 popn




                                                                                                                          Prescriptions per 100 popn
                                                                                                                     70
                                   2500
                                                                                                                     60
                                   2000
                                                                                                                     50
                                   1500                                                                              40
                                                                                                                     30
                                   1000
                                                                                                                     20
                                    500
                                                                                                                     10
                                      0                                                                              0
                                          19             19           20            20           20           20
                                            96             98           00            02           04           06
                                              -9             -9           -0            -0           -0
                                                   7              9            1             3            5



                                                                                                                                                       17
Percent of office visits by type of service ordered
   or provided by physicians in primary care
   specialties in CHCs and physician offices
                                     Physician office            Community health center



Any di agnostic/s
                  cree   ni ng service                                                       96.0
                                                                                             95.0




                Any dr ug menti                                                  78.0
                               on
                                                                                 77.0



          Any heal th educ                                          51.0
                           at ion/ 1
                                                             41.0



   Any non-medicat
                   ion     tr eatment         10.0
                                              10.0


                                         0   10   20   30   40   50    60   70   80     90   100

                                                       Percent of visits                            18
                    1   p<0.05.
Indicator performance by use of electronic
    health records in physician offices
                       Electronic health records    No electronic health records


                       100     94
                                      91            91
                        90                                  84
   Percent of visits




                        80
                        70
                        60
                        50                                                             47
                        40                                                     33
                        30
                        20
                        10
                         0                           1
                              No routine UA   No benzodiazapine for            Statin use
                                                   depression

         Note: All comparisons are significant (p< 0.01). UA is urinalysis.
         SOURCE: Linder JA et al. Archives of Internal Medicine. 2008;167:1400-1405.        19
    Percentage of OPD visits by adults 18 years
     and over with selected chronic conditions

                                                                     1996      2006


                          35
                                                                                                        30.0
                          30
      Percent of visits




                          25
                                                                                                    20.0
                          20
                                                                                         15.0
                               14.013.0
                          15                                               13.0
                                                                                     11.0
                                                                       10.0
                          10                                                                                       8.0 9.0
                                                           4.0 4.0
                           5
                                             1.0 1.0
                           0
                               Arthritis   Chronic renal    COPD      Depression/1   Diabetes/1   Hypertension/1   Obesity
                                              failure




NOTE:COPD is chronic obstructive pulmonary disease.
1 (p<0.05).
                                                                                                                             20
NAMCS and NHAMCS
   Methodology




                   21
          NAMCS Scope
• Includes non-federal, office-based
 physicians
• Excludes physicians whose main
 activity is teaching, research,
 administration, hospital-based care, or
 who are unclassified as to activity and
 those in certain specialties


                                           22
In-Scope NAMCS locations
• Freestanding clinic/urgicenter
• Community health centers
• Neighborhood and mental health
  centers
• Non-federal government clinic
• Family planning clinic
• HMO
• Faculty practice plan
• Private solo or group practice
                                   23
Out-of-Scope NAMCS locations

•   Hospital EDs and OPDs
•   Ambulatory surgicenter
•   Institutional setting (schools, prisons)
•   Industrial outpatient facility
•   Federal Government operated clinic
•   Laser vision surgery


                                               24
NAMCS Sample design

• 112 geographic PSUs
• ~ 3,700 physicians
• ~ 29,000 visits
  – 1 week reporting period



                              25
          NHAMCS Scope
• OPD was intended to be parallel to the
  NAMCS in the hospital setting
• General medicine, surgery, pediatrics,
  ob/gyn, substance abuse, and “other”
  clinics are in-scope
• Ancillary services are out of scope



                                           26
   NHAMCS Sample design

• 112 geographic PSUs
• ~ 500 hospitals
• ~ 400 EDs and ~ 250 OPDs
• ~ 37,000 ED and ~ 35,000 OPD visits
  – 4-week reporting period


                                    27
     Gaining cooperation

• Advance letters
• Endorsement letters
• Public relations materials
• Conversion of refusal


                               28
Data collection procedures

• Induction visit by Census field
    representative (FR)
•   FR training of office/hospital staff
•   Take every number
•   Prospective or retrospective method



                                           29
  Items available on the public
             use file
• Patient characteristics
  – age, race, sex, ethnicity
• Visit characteristics
  – reason for visit, diagnosis, medication
• Provider characteristics
  – physician specialty, hospital ownership
• Contextual variables based on pt zip code
  – % of poverty, median HH income, % adults
    with bachelor’s degree or higher, urban/rural
                                                30
          Repeating fields
• Reason for visit (3)
• Diagnosis (3)
• Cause of injury (3) – ED
    only
•   Ambulatory surgical
    procedures (2) – OPD
    and NAMCS only
•   Medications (8)


                             31
         Data processing

• Data are coded and keyed by SRA
    International
•   Quality control procedures
•   Edit checks by NCHS




                                    32
    Coding systems used

• A Reason for Visit Classification (NCHS)
• ICD-9-CM
  – diagnoses
  – external causes of injury
  – procedures
• Drug coding system (NCHS)

                                         33
Therapeutic classification system

 • 1985-2005, FDA’s NDC therapeutic
   classification was used
 • Limitations
   – Discontinued by FDA
   – Only one level of sub-classification



                                            34
Therapeutic classification system -
        Multum Lexicon

   • Starting with 2006 data
   • Advantages
     – Two levels of sub-classification
     – Regular updates


                                          35
    Example: Classification of
          paroxetine
• NDC
  – 0600 central nervous system
    • 0630 antidepressants

• Multum Lexicon
  – 242 psychotherapeutic agents
    • 249 antidepressants
        – 208 SSRI antidepressants



                                     36
2006 NAMCS PRF




                 37
Patient Record form (PRF)

  • Common items
  • Unique items
  • 2007-08 modifications
  • 2009-10 proposed changes


                               38
        Patient Record form
          - common items

•   Patient’s zip code
•   Date of visit
•   Date of birth
•   Sex
•   Ethnicity


                              39
        Patient Record form
          - common items
•   Race
•   Source of payment
•   Temperature and blood pressure
•   Reason for visit
•   Diagnosis
•   Injury, poisoning, adverse effect

                                        40
        Patient Record form
          – common items

•   Diagnostic/screening services
•   Medications and injections
•   Providers seen
•   Visit disposition




                                    41
     ED Patient Record form
         - unique items
•   Times – arrival, time seen, discharge
•   Residence – nursing home, homeless
•   Mode of arrival
•   Vital signs – heart rate, pulse oximetry
•   Immediacy
•   Pain level
•   Work-related
                                               42
   ED Patient Record form
       - unique items
• Previous care
  – Seen in ED in last 72 hours
  – Discharged from hospital in last 7 days
• Injury, poisoning, adverse effect
  – Cause of injury – verbatim text since 1997
  – Intentionality
• Procedure checklist
                                                 43
        ED Patient Record form
            - unique items

• Hospital admission
  –   type of unit
  –   time of admission
  –   date of discharge
  –   principal hospital discharge diagnosis
  –   discharge status



                                               44
        NAMCS and OPD PRF
           - unique items

•   Does patient use tobacco
•   Counseling/education/therapy
•   Surgical procedures
•   Time spent with physician (NAMCS only)



                                             45
      NAMCS and OPD PRF
     continuity of care items

•   Patient’s primary care physician/provider
•   Was patient referred for visit
•   Patient seen before
•   Seen how many times in past 12 months
•   Major reason for visit


                                            46
Modifications to 2007-08 ED PRF

• On                          • Off
 – Respiratory rate             – Work related visit
 – # of times seen in ED in
   last 12 months
 – Episode of care
 – Hospital admission date
 – Hospital discharge
   disposition

                                                 47
   Modifications to 2007-08
     NAMCS/OPD PRFs

• On        • Off
 – None       – Patient pregnant
                • LMP or gestation week




                                          48
            2009-10 ED PRF
              - new items

•   Dates for all times
•   On oxygen on arrival
•   Glasgow coma scale (GCS)
•   Chronic disease checklist –
    cerebrovascular disease, CHF, CRF, HIV,
    diabetes
•   Level of service
                                              49
             2009-10 ED PRF -
        new items for admitted and
         observation unit patients

•   Date and time bed was requested
•   Date and time patient left ED
•   If admitting physician is a hospitalist
•   Date and time of observation unit
    discharge

                                              50
   Modifications to 2009-10
     NAMCS/OPD PRFs
• On        • Off
 – None       – Cancer stages
              – Enrollment in a
               disease management
               program




                                    51
 2007-08 NHAMCS induction form
       - new hospital items
• Inpatient items
  – # of days in a week elective surgeries are
   scheduled
  – bed coordinator/czar
  – bed census data




                                                 52
    NHAMCS induction form
  - new ED items for 2007- 08
• Boarding
  – More than 2 hours, inpatient hallways
• Ambulance diversion
  – Regional, continue to admit elective
   surgery cases
• Procedures
  – bedside registration
  – electronic dashboard
  – zone nursing
                                            53
Which do doctors prefer?
Electronic or handwritten?




                             54
   Background on survey of
ambulatory surgery centers (ASCs)
• National Survey of
  Ambulatory Surgery (NSAS)
  – Conducted in 1994-96 and
    2006
  – Hospital-based and free-
    standing
     • 35 million visits annually (57%
       hospital-based)
• Difficult to obtain funding for
  annual NSAS
                                         55
Timeline for incorporation of ASC
   component into NHAMCS

• Conduct pilot test in August 2008 to test
  forms and sampling procedures for
  hospital-based ASCs
• Add hospital-based ASCs to 2009
  NHAMCS
• Add free-standing ASCs to 2010
  NHAMCS

                                              56
                  Overview
• NAMCS scope
• New items on the Physician Induction
    Interview (PII)
•   User considerations
•   Methodological studies
•   HIPAA
•   Data dissemination
•   NCHS Research Data Center            57
              2006 NAMCS
• Traditional sample of office-based physicians
• Stratum of 104 Community Health Centers
  (FQHC & Urban Indian Health Centers)
  – 3 @ each for a total of 312 providers
  – MDs, DOs, mid-level providers
• Increased sample to primary care physicians
  (n=50 each GFP, IM, OB/GYN)
• Oncologists
                                                  58
       NAMCS induction form
        - new items for 2006
• Number of mid-level providers
• Ask if practice has ability to perform each
 of 13 different tests and images
  – CT Scan, chemotherapy, MRI, sigmoidoscopy
• If physician sees patients during the
 evening or on the weekend


                                                59
        NAMCS induction form
     - new items for 2006 (con’t)
• Expanded the questions that ask about EMR
 functionality
  – Computerized orders for prescriptions?
    • If yes, are there warnings of drug interactions or
        contraindications provided?
    •   If yes, are prescriptions sent electronically to
        pharmacy?
  – Imaging results?
    • If yes, are electronic images returned?

                                                           60
         NAMCS induction form
      - new items for 2006 (con’t)
• Pay-4-performance:
  – Factors that are taken into account for patient care
    compensation:
     • Productivity, patient satisfaction, quality of care, and practice
       profiling
  – Performance measures on practice available to public
  – % of patient care revenue is based on bonuses, returned
    withholds, or other performance-based payments
  – % of patient care revenue from different payment
    sources
     • Usual, customary and reasonable fee-for-service; discounted fee-
       for-service; capitation; and case rates
                                                                           61
      NAMCS induction form
       - new items for 2007
• Appointments:
  – % same day appointments
  – Does practice set time aside for same day
    appointments
  – How long does it take to get an appointment
• Series of questions on HPV vaccine:
  – Recommend, sex and age groups
   recommended, and if not, why they do not
   recommend

                                                  62
      NAMCS induction form
       - new items for 2008

• How many hours do you spend in the
  office providing direct patient care?
• Which HPV vaccine does practice
  recommend using?




                                          63
User Considerations




                      64
    Encounter vs. person data

• NAMCS / NHAMCS are record-based
    surveys
•   Estimates are in terms of visits and not
    persons
•   Not population-based surveys (NHIS)
•   Cannot calculate incidence or prevalence
    rates from NAMCS / NHAMCS estimates

                                           65
        Sample weight

• Sample data MUST be weighted to
 produce national estimates
• Estimation process
  – Adjusts for survey and item nonresponse
  – Makes several ratio adjustments within and
   across physician specialties and hospitals



                                                 66
             Sampling error
• NAMCS and NHAMCS are not simple
  random samples
• Clustering effects:
  – Providers within PSUs
  – Visits within physician practice or hospital
• Must use generalized variance curve or
  special software (e.g., SUDAAN) to
  calculate SEs for all estimates, percents,
  and rates
                                                   67
        Reliability criteria
• Estimate based on at least 30 raw
 cases are reliable

• Estimate has a relative standard error
 (RSE) less than 30 percent are reliable

• Both conditions must be met

                                           68
  Ways to improve reliability
        of estimates
• Combine NAMCS, ED and OPD data to
 produce ambulatory care visit estimates

• Combine multiple years of data



                                           69
      Nonsampling error

• Frame coverage
• Reporting and processing errors
• Biases due to survey and item
 nonresponse
• Incomplete responses

                                    70
Minimizing nonsampling error

• Improve sample frame for better
    coverage
•   Encourage uniform reporting and
    eliminate ambiguities
•   Pretest survey items and procedures
•   Perform quality control procedures –
    consistency and edit checks
•   Train Census field representatives
                                           71
                  NAMCS Response rate
          75


          70
Percent




          65


          60


          55
               89 90 91 92 93 94 95 96 97 98 99 '00 '01 '02 '03 '04 '05 '06

                                          Year

                                                                              72
                NHAMCS Response rates
          100                                    ED
          90
Percent




          80                                                 OPD
          70

          60

          50
                92 93 94 95   96 97 98    99 '00 '01 '02 '03 '04 '05 '06
                                         Year

                                                                           73
        Attempts to improve
           response rate
• Publicity
• Eliminating questions that have a high
    item non-response
•   Methodological studies
•   PR material



                                           74
     Methodological studies

• NAMCS Motivational insert (2000)
• NAMCS and OPD PRF length (2001)
• Incentives test (2002)



                                     75
                 HIPAA
• No directly identifiable information
    collected
•   PHS Act 308(d) / Title 15
•   Data Use Agreement w/ Limited Dataset
•   IRB approval w/ waiver of patient
    authorization
•   Accounting Document

                                            76
                HIPAA
• 1-800 telephone number
• Respondent website
• Training
  • Written instructions
  • CD-ROM
  • Self-study
• Follow-up
                           77
  Recent & future releases

• 2006 NAMCS & NHAMCS
• Combined 2006/2007 CHC NHSR
• 2003-06 ED pediatric series report



                                       78
        Outside research
• Journal articles
  – List on Ambulatory Care web site

• Text books

• Department level publications
  – Health US

                                       79
         Microdata files
• Downloadable files
    • NAMCS, 1973-2006
    • NHAMCS, 1992-2006
• CD-ROMs
    • NAMCS, 1990-2005
    • NHAMCS, 1992-2005
• Tapes/cartridges (NTIS)
    • NAMCS, 1973-1997
    • NHAMCS, 1992-1997
                            80
    Enhanced public-use files

• New survey items and facility level data
• SAS input statements, variable labels, value
 labels, and format assignments for 1993-
 2006
• SPSS syntax files
• STATA .do and .dct files for 2002-2006

                                            81
   Enhanced public-use files
• Sample design variables
  – Masked variables for multi-stage sampling are
   available:
    • 1993-2006 NAMCS and NHAMCS

  – Starting in 2002, NAMCS & NHAMCS masked
   variables have been available for use in
   software using 1-stage sampling. Prior years
   with formula

  – Starting in 2003, we only released masked
   variables for use in software using 1-stage
                                                  82
       Design Variables—Survey Years

      2001               2002
 3- or 4-Stage       1-Stage design

design variables        variables
                   3- or 4-Stage design
                        variables
                                             2003
                                          1-Stage design
                                          variables only


                                                       83
        Average comparison ratios by
    alternative standard error method and
                 type of setting
       Type of setting       Masked 4-            Masked 1-     Masked
                            stage WOR             stage WR     SURVEY-      GVC
                             SUDAAN               SUDAAN        MEANS
       All settings        1.03                  1.03         1.02       0.84


       Physician’s         1.02                  1.02         1.01       0.93
       offices

       Hospital OPD        0.99                  1.03         1.02       0.94


       Hospital ED         1.03                  1.06         1.06       0.91

                                                                                  84
Source: Inquiry 40: 401-415 (Winter 2003/2004)
Scatter plot of masked and unmasked 4-
stage WOR SUDAAN SE for all settings
 45000000


 40000000


 35000000


 30000000


 25000000


 20000000


 15000000


 10000000


  5000000


       0
            0   5000000   10000000   15000000   20000000   25000000   30000000   35000000   40000000




                                                                                                       85
 Where to get more information


• Call Ambulatory Hospital Care
  Statistics Branch at (301) 458-4600
• Public Use Documentation
• or…


                                        86
http://www.cdc.gov/nchs/about/major/ahcd/ahcd1.htm




                                                87
NCHS Research Data Center




                            88
Why the Research Data Center?
 • Have access to information not available
  on public use files

   – Patient: zip code linked income, education,
     or urbanicity status
   – Provider: physician gender and age, board
     certification, teaching hospital, medical
     school affiliation, ED size
   – Supplement data: CCSS
   – Geographic: state and county FIPS codes
                                                   89
        Data Center - cont.
• Can merge with contextual variables
 (e.g., ARF, NHIS, Census, NHDS)

  – Health status level
  – HMO penetration
  – Physician and specialist supply
  – Medicaid reimbursement
  – Air quality
  – Percent in poverty

                                        90
          Data Center rules
• Submit a proposal
• Cannot use data to identify patients or
    providers or geographic location of
    providers
•   Cannot remove data files
•   Fee – onsite / remote / file construction



                                                91
Examples of facility-level data




                                  92
Emergency Pediatric Services and
 Equipment Supplement (EPSES)

• Funded by the Health Resources and
    Services Administration
•   Added as a supplement to the 2002-03
    and 2006 NHAMCS
    – Services related to treating children
    – Availability of pediatric supplies


                                              93
Distribution of Hospital Inpatient
       Pediatric Structure
                   Unknown         No children
                     12%              11%




                                                 No children's
                                                     ward
    Children's                                       23%
   hospital/PICU
       26%




                             Children's
                               ward
                               28%                               94
            EMR Mail Survey
• Supplement data collected on NAMCS-1
• Collected 2008 – 2009
• 4-page self administered to 2,000 additional
  physicians
• Questions:
  – Eligibility
  – EMR questions
  – Facility level questions known to affect EMR adoption
     • Practice type & size, managed care
                                                        95
EMR Use in Ambulatory Care

                        50
                                                                                             45            46
                                                        Emergency department
Percent of providers




                        40
                                                   33                                        35
                                     31
                        30           31                      Outpatient department                         29
                                                   29                                       24
                                                                              21
                        20                                     17                     Physician office
                                       18           17


                        10


                          0
                                 2001          2002          2003         2004          2005         2006



                       NOTE: Office-based physician and hospital emergency department trends are significant (p<.05).

                                                                                                                        96
     Cervical Cancer Screening
            Supplement

• Conducted in 2006-2010
• Purpose is to evaluate-
  – adherence to HPV DNA testing guidelines
  – impact of HPV vaccine on cervical cancer
    screening practices
     • Gardasil (approved 6/06 for females 9-26 years old)
     • Cervarix (approval pending)

                                                        97
Pandemic and Emergency Response
    Preparedness Supplement

• Conducted in 2008
• Supports DHHS goal for emerging health
  threats
• Assesses progress towards hospital
  preparedness for terrorist attacks, mass
  casualty incidents, pandemics, and
  natural disasters

                                             98
    I need more information !

• E-mail: pmeyer1@cdc.gov
• Website: www.cdc.gov/nchs/r&d/rdc.htm
• Call (301) 458-4375



                                          99
            Thank You
• Linda McCaig – NHAMCS data
        lmccaig@cdc.gov

• David Woodwell – NAMCS data
        dwoodwell@cdc.gov

                                100

				
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