# Presentation: 225338

## Linda McCaig and David Woodwell

2006 Data Users Conference
July 11, 2006

- 2006 Data Users Conference
- July 11, 2006

**Analyzing Data from the****NAMCS and NHAMCS**

## Overview

- Background
- Data uses
- Survey methodology
- Current and proposed survey items
- User considerations
- Methodological studies
- Data dissemination
- NCHS Research Data Center

## Slide 3

## 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

## Original NAMCS survey goals

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

## NAMCS history

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

## NHAMCS history

- Survey began in 1992
- Annual data collection  (Census)

## How are NAMCS and NHAMCS data used?

## Data 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

## Data 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

## Slide 11

## Average length of time for duration of office visits and emergency departments waiting times

- 18.6

- 38

- 18.7

- 47.4

- 0

- 10

- 20

- 30

- 40

- 50

- 60

- Minutes

- .0

- 1994                 2004                    1997              2004

- Office visit duration

- Waiting time in emergency

- departments 1/

**Average length of time for duration of office visits and emergency departments waiting times**

## Slide 13

## Percent of ED visits for transient ischemic attack in which a CT or MRI was 

- 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 2006;April 11

**Percent of ED visits for transient ischemic attack in which a CT or MRI was **
**ordered or performed**

## Percent of pediatric ED visits with analgesic prescription by pain score

- Drendel AL et al. Arch Intern Med 2006;117(5):1511-16.

## Percent of ED visits for attempted suicide according to arrival time 

- Overall

- Attempted suicide

- Doshi A et al. Ann Emerg Med 2006;46(4):369-75.

- a.m.

- p.m.

## Slide 17

## Trends in office-based visit rates by children and adolescents that included antipsychotic treatment

- Olfson M et al. Arch Gen Psyc 2006;63:679-685

## Percent of prescriptions for UTI by drug class in physician offices, OPDs, and EDs

- Kallen AJ et al. Arch Intern Med 2006;116(6):635-639.

## NAMCS and NHAMCS Methodology

## 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

## In-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

## 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

## NAMCS Sample design

- 112 geographic PSUs
- ~ 3,000 physicians
- ~ 25,000 visits
- 1 week reporting period

## 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

## 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

##   Gaining cooperation

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

## Data collection procedures

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

## Items collected on Patient Record form (PRF)

- Patient characteristics
- age, race, sex
- Visit characteristics
- reason for visit, diagnosis, medication
- Provider characteristics
- physician specialty, hospital ownership

## Repeating fields

- Reason for visit (3)
- Cause of injury (3)
- Diagnosis (3)
- Ambulatory surgical procedures (2)
- Medications (8)

## Data processing

- Data are coded and keyed by Constella Group Inc.
- Quality control procedures
- Edit checks by NCHS

## Coding 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

## Therapeutic classification system through 2004

- Since 1985, FDA’s NDC therapeutic classification has been used
- Limitations
- Discontinued by FDA
- Only one level of sub-classification

## Therapeutic classification system - Multum Lexicon

- Starting in 2005
- Advantages
-  Two levels of sub-classification
-  Regular updates

## Example: Classification of paroxetine

- NDC
- 0600 central nervous system
- 0630 antidepressants
- Multum Lexicon
- 242 psychotherapeutic agents
- 249 antidepressants
- 208 SSRI antidepressants

## 2004 NAMCS PRF

## Patient Record form - common items

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

## Patient Record form- common items

- Race
- Source of payment
- Temperature and blood pressure
- Reason for visit
- Diagnosis

## Patient Record form –common items

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

## Injury/poisoning/adverse effect items

- External cause – narrative text since 1997
- ED
- Intentionality
- Work-related

## NAMCS and OPD PRF- unique items

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

## 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
- Episode of care
- Other physicians share care

## ED Patient Record form- unique items

- Arrival time
- Time seen by physician
- Discharge time
- Mode of arrival
- Immediacy
- Pulse and orientation

## ED Patient Record form- unique items

- Presenting level of pain
- Alcohol related visit
- Work related visit
- Procedure checklist

## ED Patient Record form- continuity of care items

- Seen ED within last 72 hours
- Episode of care
- Initial or followup visit

## Modifications 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

## Modifications 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

## Modifications 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

## ED 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

## NHAMCS 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

## NHAMCS induction form- new items for 2007-08

- Critical Access Hospital (CAH)
- Transplant services
- Outsourcing of radiographs
- ED observation unit

## Examples of facility-level data

**Examples of facility-level data**

## 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

**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.

**Cross-classification of pediatric ED visits by ED pediatric visit volume and inpatient pediatric structure**

- Percent of pediatric ED visits

- ED pediatric visit volume

- Middleton KR, Burt CW.  ADR #367.

## Bioterrorism 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

## Percentage of hospitals that trained their staff in emergency response by subject area

- Niska RW, Burt CW. ADR #364.

## Slide 58

## 2003-04 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

## Slide 60

## Percent 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. 2006;*47:317-326

## Percent of office-based physicians and hospital OPDs and EDs using electronic medical records, 2001-2003

- Burt CW, Hing E.  ADR #353.

## Overview

- Updates to NAMCS and new items on the Physician Induction Interview (PII)
- User considerations
- Methodological studies
- HIPAA
- Data dissemination
- NCHS Research Data Center

## Improvements to NAMCS in 2006

- New stratum of 104 Community Health Centers (FQHC & Urban Indian Health Centers)
- 3 @ each for a total of 312 providers
- MDs, DOs, mid-level providers
- New stratum of oncologists (n=200)
- Increased sample to primary care physicians (n=50 each GFP, IM, OB/GYN)

## NAMCS induction form- new item for 2005

- Electronic medical records
- If yes, does it include...
- Patient demographics
- Computerized orders for prescriptions...

## NAMCS 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)

## NAMCS induction form- new items for 2007-08

- Length of time for appointment
- Telemedicine

## Encounter 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

## 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

## 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

## 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

## Ways to improve reliability of estimates

- Combine NAMCS, ED and OPD data to produce ambulatory care visit estimates
- Combine multiple years of data

## Nonsampling error

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

## 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

## NAMCS Response rate 

## NHAMCS Response rates

**ED**

**OPD**

## Attempts to improveresponse rate 

- Publicity
- Eliminating questions that have a high item non-response
- Methodological studies

## Methodological studies

- Complement study (1997-1999)
- Missing 11% of visits to physicians classified as not office-based
- Nonresponse follow-up survey (1998)
- Another in 2006

## Methodological studies

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

## 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

## HIPAA

- 1-800 telephone number
- Respondent website
- Training
- Written instructions
- CD-ROM
- Self-study
- Follow-up

## Impact 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

## Slide 83

## Slide 84

## Future releases

- 2005 NAMCS & NHAMCS in Spring 2007
- 2003-04 medications report ADR combining all 3 setting together

## Outside research

- Journal articles
- List on Ambulatory Care web site
- Text books
- Department level publications
- Health US

## Microdata 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

## Enhanced 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

## Enhanced 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

## Design Variables—Survey Years

**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 Years**

- *Plan to re-release years with 1-stage design variables.

## Ratio of masked to unmasked SUDAAN standard errors using four-stage WOR

- Source: *Inquiry* 40: 401-415 (Winter 2003/2004)

## Average comparison ratios by alternative standard error method and type of setting

| Type 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)

## Scatter plot of masked and unmasked 4-stage WOR SUDAAN SE for all settings 

**Scatter plot of masked and unmasked 4-stage WOR SUDAAN SE for all settings **

## Where to get more information

- Ambulatory Care information booth
- Call Ambulatory Care Statistics Branch at (301) 458-4600
- Public Use Documentation
- or...

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

## NCHS 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

## 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

## 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

## I need more information !

- Visit the Research Data Center booth
- E-mail:  rdca@cdc.gov
- Website:   www.cdc.gov/nchs/r&d/rdc.htm
- Call (301) 458-4277

## Thank You	

- Linda McCaig – NHAMCS data
**	****	****	**lmccaig@cdc.gov
- David Woodwell – NAMCS data
**	****	****	**dwoodwell@cdc.gov