overview of the namcs and nhamcs
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Overview of the NAMCS and NHAMCS. Linda McCaig and David Woodwell Ambulatory Care Statistics Branch Division of Health Care Statistics. Overview. Background Data uses Survey methodology Current and proposed survey items User considerations Methodological studies Data dissemination - PowerPoint PPT PresentationTRANSCRIPT
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Linda McCaig and David Woodwell
Ambulatory Care Statistics BranchDivision of Health Care Statistics
Overview of the NAMCSOverview of the NAMCSand NHAMCSand NHAMCS
U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICESCenters for Disease Control and PreventionNational Center for Health Statistics
U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICESCenters for Disease Control and PreventionNational Center for Health Statistics
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OverviewOverviewBackgroundData usesSurvey methodologyCurrent and proposed survey itemsUser considerationsMethodological studiesData disseminationNCHS Research Data Center
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National probability sample National probability sample surveyssurveys
National Ambulatory Medical Care Survey (NAMCS)– Patient visits to non-federal office-
based physiciansNational Hospital Ambulatory
Medical Care Survey (NHAMCS)– Patient visits to EDs and OPDs of non-
federal short-stay hospitals
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Original NAMCS survey Original NAMCS survey goalsgoals
• National statistics• Professional education• Health policy formulation• Medical practice management• Quality assurance
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NAMCS historyNAMCS history
Survey began in 1973 Annual data collection through
1981 (NORC)Conducted in 1985 (NORC)Annual began again in 1989
(Census)
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NHAMCS historyNHAMCS history
Survey began in 1992 Annual data collection (Census)
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How are NAMCS and How are NAMCS and NHAMCS data used?NHAMCS data used?
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Data usesData usesUnderstand health care practiceExamine the quality of careTrack certain conditionsFind health disparitiesMeasure Healthy People 2010
objectivesServe as benchmark for states
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Data usersData usersOver 100 journal publications in last 2
yearsMedical associationsGovernment agenciesHealth services researchersUniversity and medical schoolsBroadcast and print media
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Total Ambulatory Care Visits
SOURCE: CDC/NCHS, NAMCS and NHAMCS, 2001.
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Annual rate of injury-related Annual rate of injury-related ED visits for seniors by patient ED visits for seniors by patient
residenceresidence
Age in yearsInstitution CommunityNumber of visits per 100 persons
65-79 41 880+ 37 14
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Percent of physician office Percent of physician office visits by type of cardiac visits by type of cardiac rhythm modifying agentrhythm modifying agent
01020304050607080
Ventricular ratecontrol
Sinus rhythmmaintenance
Neither
Perc
ent o
f vis
its
1991-92 1999-00
Fang et al. Arch Intern Med 2004;164(1):55-60.Fang et al. Arch Intern Med 2004;164(1):55-60.
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Percent of selected ED visit Percent of selected ED visit characteristics among released characteristics among released
patients who had a blood culturepatients who had a blood cultureVisitcharacteristic
Antibiotics prescribed
Antibiotics not prescribed
Total
Fever 19% 17% 36%No fever 28% 36% 64%
Total 47% 53% 100%
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Potentially inappropriate drug Potentially inappropriate drug prescribing at elderly physician prescribing at elderly physician
office visitsoffice visits
01234567
1 2 3 4 5 6
Number of prescription drugs
Adj
uste
d od
ds ra
tio
Goulding. Arch Intern Med 2004;164(3):305-312.Goulding. Arch Intern Med 2004;164(3):305-312.
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Number and rate of physician Number and rate of physician office visits for diabetesoffice visits for diabetes
0
5
10
15
20
25
30
1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002
Year
Number of visits in millions
Rate per 100 persons
Grant et al. Arch Intern Med 2004;164(10):1134-1139.Grant et al. Arch Intern Med 2004;164(10):1134-1139.
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Annual rate of injury-related ED Annual rate of injury-related ED visits for children by diagnosisvisits for children by diagnosis
0
5
10
15
20
25
30
1993/94 1995/96 1997/98 1999/00 2001/02
Year
Visi
ts p
er 1
00 p
erso
ns Head wound
Other wound
IntracranialPoisoning
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Variations in drug mention rates for Variations in drug mention rates for selected therapeutic classes by source selected therapeutic classes by source
of paymentof payment
0 5 10 15 20 25Drug mentions per 100 visits
Uninsured Private
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Variations in drug mention rates for Variations in drug mention rates for selected therapeutic classes by MSA selected therapeutic classes by MSA
statusstatus
0 5 10 15 20 25
Pain relief
Otologics
Antimicrobials
Drug mentions per 100 visits
Non-MSA MSA
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HP2010 Objectives on HP2010 Objectives on antibiotic prescribingantibiotic prescribing
Ear infections(Antibiotics per 1000 persons)
Common cold(Antibiotics per 1000 persons)
Baseline 693 251998/99 545 18
2000/01 595 18Target 561 13
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NAMCS and NHAMCS NAMCS and NHAMCS MethodologyMethodology
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NAMCS ScopeNAMCS 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
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In-Scope NAMCS locations In-Scope NAMCS locations Freestanding clinic/urgicenterFederally qualified health centerNeighborhood and mental health
centersNon-federal government clinicFamily planning clinicHMOFaculty practice planPrivate solo or group practice
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Out-of-Scope NAMCS locationsOut-of-Scope NAMCS locations
Hospital EDs and OPDsAmbulatory surgicenterInstitutional setting (schools, prisons)Industrial outpatient facilityFederal Government operated clinicLaser vision surgery
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NAMCS Sample designNAMCS Sample design
112 geographic PSUs3,000 physicians25,000 visits
– 1 week reporting period
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NHAMCS Scope NHAMCS Scope OPD was intended to be parallel to the
NAMCS in the hospital settingGeneral medicine, surgery, pediatrics,
ob/gyn, substance abuse, and “other” clinics are in-scope
Ancillary services are out of scope
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NHAMCS Sample designNHAMCS Sample design
112 geographic PSUs500 hospitals400 EDs and 250 OPDs37,000 ED and 35,000
OPD visits– 4-week reporting period
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Gaining cooperationGaining cooperation
Advance lettersEndorsement lettersPublic relations materialsConversion of refusal
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Data collection proceduresData collection proceduresInduction visit by Census field
representative (FR) FR training of office/hospital staffTake every numberProspective or retrospective method
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Items collected on Patient Items collected on Patient Record form (PRF)Record form (PRF)
Patient characteristics– age, race, sex
Visit characteristics– reason for visit, diagnosis, medication
Provider characteristics– physician specialty, hospital ownership
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Repeating fieldsRepeating fields
Reason for visit (3) Cause of injury (3) Diagnosis (3) Ambulatory surgical
procedures (2) Medications (8)
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Data processingData processing
Data are coded and keyed by Constella Group Inc. (CG)
Quality control proceduresEdit checks by NCHS
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Coding systems usedCoding systems usedA Reason for Visit Classification (NCHS)ICD-9-CM
– diagnoses– external causes of injury– procedures
Drug coding system (NCHS)National Drug Code Directory
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NAMCS and NHAMCS NAMCS and NHAMCS 2001-2004 PRFs2001-2004 PRFs
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Patient Record formPatient Record form - common items - common items
Patient’s zip codeDate of visitDate of birthSexEthnicity
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Patient Record formPatient Record form- common items- common items
RaceSource of paymentReason for visitDiagnosis
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Patient Record form –Patient Record form –common itemscommon items
Diagnostic/screening servicesMedications and injectionsProviders seenVisit disposition
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Injury/poisoning/adverse effect Injury/poisoning/adverse effect itemsitems
External cause – narrative text since 1997
ED– intentionality– work related
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NAMCS and OPD PRFNAMCS and OPD PRF- unique items- unique items
Does patient use tobaccoCounseling/education/therapySurgical proceduresTime spent with physician (NAMCS
only)
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2001-2004 NAMCS and OPD PRF2001-2004 NAMCS and OPD PRFcontinuity of care items continuity of care items
Patient’s primary care physician/providerWas patient referred for visitPatient seen beforeSeen how many times in past 12 monthsMajor reason for visitEpisode of careOther physicians share care
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ED Patient Record formED Patient Record form- unique items- unique items
Arrival timeDischarge timeTime seen by physicianMode of arrivalImmediacy
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ED Patient Record formED Patient Record form- unique items- unique items
Presenting level of painAlcohol related visitWork related visitProcedure checklist
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ED Patient Record formED Patient Record form- continuity of care items- continuity of care items
Seen ED within last 72 hoursEpisode of care
– Initial or followup visit
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Recycled items onRecycled items on 2003-04 ED PRF 2003-04 ED PRF
On– Time seen by
physician – Mode of arrival– Presenting level
of pain
Off– Visit related to an
adverse drug event
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NAMCS and OPD PRF NAMCS and OPD PRF revisions 2005-06 – revisions 2005-06 –
emphasis on chronic emphasis on chronic conditionsconditions
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NAMCS and OPD PRF-NAMCS and OPD PRF- new items for 2005-06 new items for 2005-06
– Arthritis– Asthma– Cancer– Cerebrovascular
disease– CHF– Chronic renal failure– COPD
– Depression– Diabetes– Hyperlipidemia– Hypertension– Ischemic heart
disease– Obesity– Osteoporosis
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NAMCS and OPD PRF NAMCS and OPD PRF - new items for 2005-06- new items for 2005-06
Vital signs– Height– Weight– Temperature– Blood pressure
Disease management programMedication – new or continued
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ED PRFED PRF- new items for 2005-06- new items for 2005-06
HomelessDischarged from any hospital within
last 7 daysMedication given in ED or
prescribed at dischargeReason patient was transferred
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ED PRFED PRF- new items for 2005-06- new items for 2005-06
Admit to hospital– Critical care/Intervention/Other bed– Hospital admission time– Hospital discharge date– Principal hospital discharge diagnosis– Alive/Dead
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Examples of Examples of Collaboration with Other Collaboration with Other Government AgenciesGovernment Agencies
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Emergency Pediatric Services Emergency Pediatric Services and Equipment Supplement and Equipment Supplement
(EPSES)(EPSES)Funded by the Health Resources and
Services AdministrationAdded as a supplement to the 2002-03
NHAMCS– Services related to treating children– Availability of pediatric supplies
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Medical Specialty Number of EDs
Percent of EDs
Board Certified Emergency Medicine Attending Physician
3,550 73
Board Certified Pediatric Emergency Medicine Attending Physician
1,270 26
Board Certified Pediatric Attending Physician 3,249 67
Attending Physician Specialty Attending Physician Specialty (available 24/7 in-house or on-call) (available 24/7 in-house or on-call)
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Bioterrorism and mass Bioterrorism and mass casualty preparednesscasualty preparedness
Funded by the DHHS Assistant Secretary for Planning and Evaluation
2003-4 NAMCS Physician 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
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2003-04 NHAMCS Supplements2003-04 NHAMCS Supplements
Hospital inpatient occupancy rateED capacity and staffing
– Number of treatment spaces– Percent of vacant nursing positions– Physicians employed by hospital or
contractorAmbulance diversion
– Percent of days on diversion– Mean number of hours on diversion
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Percent distribution of hospital Percent distribution of hospital emergency departments by safety-net emergency departments by safety-net
criteriacriteria
0 10 20 30 40 50 60 70
Low safety net
High combined
High Medicaid/low uninsured
High uninsured/low Medicaid
High Medicaid/low unisured
Percent of hospital emergency departments
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Percent distribution of emergency Percent distribution of emergency department visits by selected department visits by selected
characteristics according to size characteristics according to size of annual visit volumeof annual visit volume
0
20
4060
80
100
Electronicmedicalrecords
Automateddrug
dispensing
Board-certifiedEM physicians
Perc
ent d
istr
ibut
ion
SmallMediumLarge
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Percent of physicians accepting Percent of physicians accepting new patients by pay sourcenew patients by pay source
0
20
40
60
80
100
Medicare Medcaid
Perc
ent o
f phy
sici
ans
Primary care Surgical Medical
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OverviewOverviewUser considerations
– Encounter vs. person data– Sampling error– Nonsampling error
Methodological studiesHIPAAData disseminationNCHS Research Data Center
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Encounter vs. person dataEncounter vs. person data
NAMCS and NHAMCS are record-based surveys
Not population-based surveys (NHIS)Estimates are in terms of visits and not
personsCannot calculate incidence or
prevalence rates from our estimates
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Sample weightSample 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
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Sampling errorSampling 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.
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Reliability criteriaReliability criteriaEstimates based on at least 30 raw
cases are reliable
Estimates with a relative standard error (RSE) less than 30 percent are reliable
Both conditions must be met
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Ways to improve reliability Ways to improve reliability of estimatesof estimates
Combine NAMCS, ED and OPD data to produce ambulatory care visit estimates
Combine multiple years of data
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Nonsampling errorNonsampling error
Frame coverageReporting and processing errorsBiases due to survey and item
nonresponseIncomplete responses
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Minimizing nonsampling errorMinimizing nonsampling error
Improve sample frame for better coverage
Encourage uniform reporting and eliminate ambiguities
Pretest survey items and proceduresPerform quality control procedures –
consistency and edit checksTrain Census field representatives
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NAMCS Response rate NAMCS Response rate
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60
65
70
75
89 90 91 92 93 94 95 96 97 98 99 '00 '01 '02
Year
Perc
ent
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NHAMCS Response ratesNHAMCS Response rates
50
60
70
80
90
100
92 93 94 95 96 97 98 99 '00 '01 '02
Year
Perc
ent
ED
OPD
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Attempts to improve response Attempts to improve response rate rate
Publicity Eliminating questions that have a high
item non-responseMethodological studies
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Methodological studiesMethodological studies
• Complement study 1997-1999• 500 physicians in each year• 17% of classified as nonoffice-based saw
patients• Represented 11% of total• Difference not accounted for in weighting
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Methodological studiesMethodological studies
• NAMCS Motivational insert• Conducted last half of 2000• Insert (n=513); no insert (n=499)• RR - 68% vs. 64%• No difference in RR
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Methodological studiesMethodological studies• NAMCS and OPD PRF length
• Conducted 2001• NAMCS: short (n=941); long (n=969)• OPD: short (n=132); long (n=129)• NAMCS RR - 68% (short) vs. 62% (long) • NAMCS short PRF had a higher RR• No effect on RR in OPD
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Methodological studiesMethodological studies
• Incentives test• Conducted last 3 quarters of 2002• 3 groups: control (n=418), gift (n=401), and
monetary (n=456)• RR – 73%, 68%, and 73%, respectively• No difference in RR between incentive
groups
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HIPAAHIPAA• 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
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HIPAAHIPAA• 1-800 telephone number• Respondent website
• www.cdc.gov/namcs• www.cdc.gov/nhamcs
• Training• Written instructions• CD-ROM• Self-study
• Follow-up
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Impact of HIPAA on 2003 Impact of HIPAA on 2003 NAMCS and NHAMCSNAMCS and NHAMCS
• Induction process in hospitals is longer due to additional levels of approval process
• Less likely to allow FR abstraction• Response rate not affected• 2004 may be more difficult…
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Outside researchOutside research
Journal articles– List on Ambulatory Care web site
Text books
Department level publications– Health US
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Microdata filesMicrodata filesDownloadable files
NAMCS, 1973-2002NHAMCS, 1992-2002
CD-ROMsNAMCS, 1990-2002NHAMCS, 1992-2001 (2002 in Aug.)
Tapes/cartridges (NTIS)NAMCS, 1973-1997NHAMCS, 1992-1997
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Enhanced public-use filesEnhanced public-use filesNew survey items and facility level data
SAS input statements, variable labels, value labels, and format assignments– 1993 – 2002 for NAMCS– 1995 – 2002 for NHAMCS
SPSS & STATA input statements, variable labels, value labels, and format assignments in 2002
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Enhanced public-use filesEnhanced public-use filesSample design variables
– Masked variables for multi-stage sampling are available:
1993-2002 NAMCS 1995-2002 NHAMCS
– In 2002, NAMCS & NHAMCS will have masked variables for use in software using 1-stage sampling. Prior years with formula
– In 2003, we will only release masked variables for use in software using 1-stage
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2001*3- & 4-Stage
design variables
2003
2002
1-Stage design
variables only
1-Stage design
variables
3- & 4-Stage design
variables
Design Variables—Survey YearsDesign Variables—Survey Years
*Plan to re-release years with 1-stage design variables.
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Ratio of masked to unmasked SUDAAN standard errors using four-stage WOR
Source: Inquiry 40: 401-415 (Winter 2003/2004)
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Average comparison ratios by alternative standard error method and
type of settingType of setting
Masked 4-stage WOR SUDAAN
Masked 1-stage WR SUDAAN
Masked SURVEY- MEANS
GVC
All settings 1.03 1.03 1.02 0.84
Physician’s offices
1.02 1.02 1.01 0.93
Hospital OPD 0.99 1.03 1.02 0.94
Hospital ED 1.03 1.06 1.06 0.91
Source: Inquiry 40: 401-415 (Winter 2003/2004)
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0
5000000
10000000
15000000
20000000
25000000
30000000
35000000
40000000
45000000
0 5000000 10000000 15000000 20000000 25000000 30000000 35000000 40000000
Scatter plot of masked and unmasked 4-stage WOR SUDAAN SE for all settings
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Future releasesFuture releases
2003 NAMCS & NHAMCS in Spring 2005
All settings Series report in Fall 2004 with NAMCS data for primary care and surgical and medical specialties
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Where to get more Where to get more informationinformation
Ambulatory Care information boothAmbulatory Care website
– Ambulatory Care listserveCall Ambulatory Care Statistics Branch
at (301) 458-4600
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http://www.cdc.gov/nchs/about/major/ahcd/ahcd1.htmhttp://www.cdc.gov/nchs/about/major/ahcd/ahcd1.htm
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NCHS Research NCHS Research Data CenterData Center
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Why the Research Data Center?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, provider weight
– Geographic: state and county FIPS codes
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Data Center-Data Center-cont.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
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Data Center rulesData Center rulesSubmit a proposalCannot use data to identify patients or
providers or geographic location of providers
Cannot remove data filesFee – onsite / remote / file construction
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I need more information !I need more information !
Visit the Research Data Center booth
E-mail: [email protected]
Website: www.cdc.gov/nchs/r&d/rdc.htm
Call (301) 458-4277
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Thank YouThank YouLinda McCaig – NHAMCS data
David Woodwell – NAMCS data
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