Title: Linda McCaig and David Woodwell
1Analyzing Data from theNAMCS and NHAMCS
- Linda McCaig and David Woodwell
- 2006 Data Users Conference
- July 11, 2006
2Overview
- Background
- Data uses
- Survey methodology
- Current and proposed survey items
- User considerations
- Methodological studies
- Data dissemination
- NCHS Research Data Center
3(No Transcript)
4National 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
5Original NAMCS survey goals
- National statistics
- Professional education
- Health policy formulation
- Quality assurance
6NAMCS history
- Survey began in 1973
- Annual data collection through 1981 (NORC)
- Conducted in 1985 (NORC)
- Annual began again in 1989 (Census)
7NHAMCS history
- Survey began in 1992
- Annual data collection (Census)
8How are NAMCS and NHAMCS data used?
9Data uses
- Understand health care practices
- Track certain conditions and prescribing patterns
- Find health disparities
- Examine the quality of care
- Measure Healthy People 2010 objectives
- Serve as benchmark for states
10Data users
- Over 100 journal publications in last 2 years
- Medical associations
- Government agencies
- Institute of Medicine
- Health services researchers
- University and medical schools
- Broadcast and print media
11(No Transcript)
12Average length of time for duration of office
visits and emergency departments waiting times
60
47.4
50
38
.0
40
Minutes
30
18.6
18.7
20
10
0
1994 2004 1997
2004
Waiting time in emergency
Office visit duration
departments 1/
1/ Significant increase since 1997 (plt.01)
13(No Transcript)
14Percent of ED visits for transient ischemic
attack in which a CT or MRI was ordered or
performed
Source National Hospital Ambulatory Medical Care
Survey, 1992-2001 Citation Edlow JA, Kim S,
Pelletier AJ, Camargo CA Jr. National study on
emergency department visits for Transient
Ischemic Attack, 1992-2001. Acad Emer Med
2006April 11
15Percent of pediatric ED visits with analgesic
prescription by pain score
Drendel AL et al. Arch Intern Med
2006117(5)1511-16.
16Percent of ED visits for attempted suicide
according to arrival time
Overall
Attempted suicide
a.m.
p.m.
Doshi A et al. Ann Emerg Med 200646(4)369-75.
17(No Transcript)
18Trends in office-based visit rates by children
and adolescents that included antipsychotic
treatment
Olfson M et al. Arch Gen Psyc 200663679-685
19Percent of prescriptions for UTI by drug class in
physician offices, OPDs, and EDs
Kallen AJ et al. Arch Intern Med
2006116(6)635-639.
20NAMCS and NHAMCS Methodology
21NAMCS 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
22In-Scope NAMCS locations
- Freestanding clinic/urgicenter
- Federally qualified health center
- Neighborhood and mental health centers
- Non-federal government clinic
- Family planning clinic
- HMO
- Faculty practice plan
- Private solo or group practice
23Out-of-Scope NAMCS locations
- Hospital EDs and OPDs
- Ambulatory surgicenter
- Institutional setting (schools, prisons)
- Industrial outpatient facility
- Federal Government operated clinic
- Laser vision surgery
24NAMCS Sample design
- 112 geographic PSUs
- 3,000 physicians
- 25,000 visits
- 1 week reporting period
25NHAMCS 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
26NHAMCS 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
28Data collection procedures
- Induction visit by Census field representative
(FR) - FR training of office/hospital staff
- Take every number
- Prospective or retrospective method
29Items collected on Patient Record form (PRF)
- Patient characteristics
- age, race, sex
- Visit characteristics
- reason for visit, diagnosis, medication
- Provider characteristics
- physician specialty, hospital ownership
30Repeating fields
- Reason for visit (3)
- Cause of injury (3)
- Diagnosis (3)
- Ambulatory surgical procedures (2)
- Medications (8)
31Data processing
- Data are coded and keyed by Constella Group Inc.
- Quality control procedures
- Edit checks by NCHS
32Coding systems used
- A Reason for Visit Classification (NCHS)
- ICD-9-CM
- diagnoses
- external causes of injury
- procedures
- Drug coding system (NCHS)
- National Drug Code Directory
33Therapeutic classification system through 2004
- Since 1985, FDAs NDC therapeutic classification
has been used - Limitations
- Discontinued by FDA
- Only one level of sub-classification
34Therapeutic classification system - Multum Lexicon
- Starting in 2005
- Advantages
- Two levels of sub-classification
- Regular updates
35Example Classification of paroxetine
- NDC
- 0600 central nervous system
- 0630 antidepressants
- Multum Lexicon
- 242 psychotherapeutic agents
- 249 antidepressants
- 208 SSRI antidepressants
362004 NAMCS PRF
37Patient Record form - common items
- Patients zip code
- Date of visit
- Date of birth
- Sex
- Ethnicity
38Patient Record form- common items
- Race
- Source of payment
- Temperature and blood pressure
- Reason for visit
- Diagnosis
39Patient Record form common items
- Diagnostic/screening services
- Medications and injections
- Providers seen
- Visit disposition
40Injury/poisoning/adverse effect items
- External cause narrative text since 1997
- ED
- Intentionality
- Work-related
41NAMCS and OPD PRF- unique items
- Does patient use tobacco
- Counseling/education/therapy
- Surgical procedures
- Time spent with physician (NAMCS only)
42NAMCS and OPD PRFcontinuity of care items
- Patients primary care physician/provider
- Was patient referred for visit
- Patient seen before
- Seen how many times in past 12 months
- Major reason for visit
- Episode of care
- Other physicians share care
43ED Patient Record form- unique items
- Arrival time
- Time seen by physician
- Discharge time
- Mode of arrival
- Immediacy
- Pulse and orientation
44ED Patient Record form- unique items
- Presenting level of pain
- Alcohol related visit
- Work related visit
- Procedure checklist
45ED Patient Record form- continuity of care items
- Seen ED within last 72 hours
- Episode of care
- Initial or followup visit
46Modifications to 2005-06 ED PRF
- On
- Patient residence
- Discharged from any hospital within last 7 days
- Drug given in ED or prescribed at discharge
- Reason patient was transferred
- Off
- Alcohol related visit
- Episode of care
47Modifications to 2005-06 ED PRF
- Information on patients admitted to from the ED
- Type of unit
- Admission time
- Hospital discharge date
- Principal hospital discharge diagnosis
- Discharged dead or alive
48Modifications to 2005-06 NAMCS/OPD PRFs
- On
- Pregnant
- (LMP) or gestation week
- Chronic disease checklist
- Disease management program
- Height and weight
- Medications new or continued
- Non-medication treatment
- Off
- Episode of care
- Do physicians share care
- Cause of injury
49ED PRF- new items for 2007-08
- Respiratory rate
- How many times seen in this ED in last 12 months?
- Type of MRI and CT scan
- Head or other
- Procedure checkboxes more specific
50NHAMCS induction form- new items for 2005-06
- Electronic medical records
- Mass casualty preparedness
- Drills, exercises
- ED staffing, capacity, and ambulance diversion
- Percent of ED board certified physicians
- Number of hours ED was on ambulance diversion
- Plans to expand ED physical space
51NHAMCS induction form- new items for 2007-08
- Critical Access Hospital (CAH)
- Transplant services
- Outsourcing of radiographs
- ED observation unit
52Examples of facility-level data
53Emergency 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
54 Cross-classification of EDs by ED pediatric visit
volume and inpatient pediatric structure
ED pediatric visit volume
Percent of EDs
Middleton KR, Burt CW. ADR 367.
55 Cross-classification of pediatric ED visits by ED
pediatric visit volume and inpatient pediatric
structure
ED pediatric visit volume
Percent of pediatric ED visits
Middleton KR, Burt CW. ADR 367.
56Bioterrorism and mass casualty preparedness
- Funded by the DHHS ASPE
- 2003-05 NAMCS Induction Interview
- Diagnosis of terror-related conditions
- Assistance in making a diagnosis
- Reporting a suspect case
- 2003-04 NHAMCS supplement
- Hospital response plan, training, and resources
57Percentage of hospitals that trained their staff
in emergency response by subject area
Niska RW, Burt CW. ADR 364.
58(No Transcript)
592003-04 NHAMCS Supplements
- Hospital inpatient occupancy rate
- ED capacity and staffing
- Number of treatment spaces
- Percent of vacant nursing positions
- Physicians employed by hospital or contractor
- Ambulance diversion
60(No Transcript)
61Percent distribution of EDs by time on ambulance
diversion and metropolitan statistical area status
Time on diversion
Percent of EDs
Burt CW, McCaig LF, Valverde RH. Ann Emerg Med.
200647317-326
62Percent of office-based physicians and hospital
OPDs and EDs using electronic medical records,
2001-2003
Burt CW, Hing E. ADR 353.
63Overview
- Updates to NAMCS and new items on the Physician
Induction Interview (PII) - User considerations
- Methodological studies
- HIPAA
- Data dissemination
- NCHS Research Data Center
64Improvements to NAMCS in 2006
- New stratum of 104 Community Health Centers (FQHC
Urban Indian Health Centers) - 3 _at_ each for a total of 312 providers
- MDs, DOs, mid-level providers
- New stratum of oncologists (n200)
- Increased sample to primary care physicians (n50
each GFP, IM, OB/GYN)
65NAMCS induction form- new item for 2005
- Electronic medical records
- If yes, does it include
- Patient demographics
- Computerized orders for prescriptions
66NAMCS induction form- new items for 2006
- On-site tests or procedures
- Electronic medical records
- If yes, does it include
- Patient demographics
- Computerized orders for prescriptions
- If yes, Are there warning for drug interactions
- Pay for performance (P4P)
67NAMCS induction form- new items for 2007-08
- Length of time for appointment
- Telemedicine
68Encounter vs. person data
- NAMCS and 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 our estimates
69Sample 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
70Sampling 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
71Reliability 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
72Ways to improve reliability of estimates
- Combine NAMCS, ED and OPD data to produce
ambulatory care visit estimates - Combine multiple years of data
73Nonsampling error
- Frame coverage
- Reporting and processing errors
- Biases due to survey and item nonresponse
- Incomplete responses
74Minimizing 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
75NAMCS Response rate
76NHAMCS Response rates
ED
OPD
77Attempts to improveresponse rate
- Publicity
- Eliminating questions that have a high item
non-response - Methodological studies
78Methodological studies
- Complement study (1997-1999)
- Missing 11 of visits to physicians classified as
not office-based - Nonresponse follow-up survey (1998)
- Another in 2006
79Methodological studies
- NAMCS Motivational insert (2000)
- NAMCS and OPD PRF length (2001)
- Incentives test (2002)
80HIPAA
- 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
81HIPAA
- 1-800 telephone number
- Respondent website
- Training
- Written instructions
- CD-ROM
- Self-study
- Follow-up
82Impact of HIPAA on NAMCS and NHAMCS
- Induction process in hospitals is longer due to
additional levels of approval process - Less likely to allow FR abstraction
- Response rate not directly affected
- Easy reason to refuse
83(No Transcript)
84(No Transcript)
85Future releases
- 2005 NAMCS NHAMCS in Spring 2007
- 2003-04 medications report ADR combining all 3
setting together
86Outside research
- Journal articles
- List on Ambulatory Care web site
- Text books
- Department level publications
- Health US
87Microdata files
- Downloadable files
- NAMCS, 1973-2004
- NHAMCS, 1992-2004
- CD-ROMs
- NAMCS, 1990-2003
- NHAMCS, 1992-2003
- Tapes/cartridges (NTIS)
- NAMCS, 1973-1997
- NHAMCS, 1992-1997
88Enhanced public-use files
- New survey items and facility level data
- SAS input statements, variable labels, value
labels, and format assignments for 1993-2004 - SPSS syntax files, Stata .do and .dct files for
2002-2004
89Enhanced public-use files
- Sample design variables
- Masked variables for multi-stage sampling are
available - 1993-2004 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 - Stating in 2003, we only released masked
variables for use in software using 1-stage
90Design VariablesSurvey Years
2001
2002
1-Stage design variables 3- 4-Stage design
variables
3- 4-Stage design variables
2003
1-Stage design variables only
Plan to re-release years with 1-stage design
variables.
91Ratio of masked to unmasked SUDAAN standard
errors using four-stage WOR
Source Inquiry 40 401-415 (Winter 2003/2004)
92Average comparison ratios by alternative standard
error method and type of setting
Source Inquiry 40 401-415 (Winter 2003/2004)
93Scatter plot of masked and unmasked 4-stage WOR
SUDAAN SE for all settings
94Where to get more information
- Ambulatory Care information booth
- Call Ambulatory Care Statistics Branch at (301)
458-4600 - Public Use Documentation
- or
95http//www.cdc.gov/nchs/about/major/ahcd/ahcd1.htm
96NCHS Research Data Center
97Why 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, provider weight - Geographic state and county FIPS codes
98Data 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
99Data 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
100I need more information !
- Visit the Research Data Center booth
- E-mail rdca_at_cdc.gov
- Website www.cdc.gov/nchs/rd/rdc.htm
- Call (301) 458-4277
101Thank You
- Linda McCaig NHAMCS data
- lmccaig_at_cdc.gov
- David Woodwell NAMCS data
- dwoodwell_at_cdc.gov