Transcript No Slide Title - AcademyHealth

Analyzing NCHS Drug Data:
NHANES and N/HAMCS
Amy B. Bernstein, Sc.D.
Presented at the AcademyHealth Annual
Research Meeting
San Diego, California
June 6, 2004
National Center for Health Statistics
Topics
•
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Definition of “drug”
Issues in drug utilization analyses
Coding issues
Examples of trend analyses
Definition of “Drug”
NHANES
• A drug is defined as a unique
combination of generic ingredients.
N/HAMCS
• Recorded on visit record and abstracted
verbatim
NHANES Drug Data
• All drugs used in the past month at time of
survey interview
• Only prescription drugs are included, with a
few exceptions
• Example:
--penicillin
--penicillin, clavulanate potassium
 More closely approximates “prevalence”
of use
N/HAMCS Drug Data
•
Up to six drugs recorded (until 2003)—
possible biases for drugs that are not
salient to the physician or patient (e.g.,
PRN drugs)
•
Both prescription and non-prescription
drugs are included
•
No information is available on compliance
or use
 Approximates prescribing patterns of drugs
associated with medical care visits
Issues in Drug Utilization Analyses
NHANES
Strengths:
•
Nationally representative and populationbased
•
Examination, laboratory and questionnaire
data on conditions, biochemical markers,
nutrition, health status, and other items
•
Respondent-reported sociodemographic
data (e.g., race and ethnicity are collected
from respondent)
Issues in Drug Utilization Analyses
NHANES
Possible Limitations:
• Small sample size for less frequently
prescribed drugs and small population
subgroups
• No trade names that help to determine
therapeutic use on public use file
• Respondents may not report use of
some drugs
Issues in Drug Utilization Analyses
N/HAMCS
Strengths:
• Nationally representative
• Physician/hospital characteristics
• Conditions (from medical record—but
limited number)
• Selected procedures and tests
• Relatively large sample size of visits
Issues in Drug Utilization Analyses
N/HAMCS
Possible Limitations:
• Limited sociodemographic data
• Race/ethnicity data are reported by provider,
not patient
• Limited information on episodes or continuity
of care
• No data on compliance or actual utilization
• Censoring of both drugs and diagnoses
• Drugs are recorded verbatim from visit
records, with possible misspelling
Issues in Drug Utilization Analyses
N/HAMCS
Factors influencing N/HAMCS counts of
drugs:
• Person must have visited a physician or OPD
• The more visits made for a specific condition
requiring a specific drug, the greater the count
of that drug on the N/HAMCS
Coding Drug Data
Into Therapeutic Classes: Why?
Therapeutic classes are useful in
determining trends in treatment because:
• There may be competing
for the same condition
drugs that are used
• Guidelines may suggest a class of drugs for
treatment of a condition, not a specific drug
• There are too many individual drugs to analyze
each individually!
 Ideally, one wants to group “like” drugs
together
FDA’s National Drug Code (NDC)
Therapeutic Classes
•
Used by both N/HAMCS and NHANES on public
use files
•
Code set is nonproprietary and downloadable
from the FDA website
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Identifies each of 20 major drug classes
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Specific four-digit categories represent the
breakouts of the general category (e.g., 0346,
Penicillins).
Two-digit categories are general and represent all
sub-categories (e.g., 03, Antimicrobial agents)
Coding Issues
With FDA’s National Drug Code (NDC)
Therapeutic Classes
Some therapeutic categories are based on indication,
while others are based on chemical composition or
chemical mechanism
--Examples:
NDC Class 1374/Anticonvlusants
or
NDC Class 1945/Cough and Cold remedies
or
NDC Class 0512/Beta Blocker
FDA’s Therapeutic Drug
Class Codes
•
When using any therapeutic drug class codes, need
to review the drugs that are included under that
category.
•
Ask yourself- “Is this the list of products I am
interested in?”
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When using NAMCS/NHAMCS or NHANES, look at
FDA’s therapeutic drug classes and each drug under
those classes.
• Is the drug class coding sufficient for your research?
• If not, manually review drugs and recategorize using
the generic name codes
Coding Issues
• Only generic ingredients provided on NHANES
public use file, and some N/HAMCS drugs are
reported as generic drugs (e.g., “aspirin”)
• “Main reason for use” is collected
into ICD-9-CM classification
•
and coded
Some drugs have the same ingredients but
different strengths, or different routes of
administration that help determine therapeutic
use
Examples: Asthma drugs
Coding Issues
Changes Over Time
• N/HAMCS 1980-2001:
one NCD
therapeutic class on PUF for each drug
recorded
• N/HAMCS 2002-2006: up to three NCD
therapeutic classes on PUF for each drug
recorded
• NHANES 1988-94:
three NDC therapeutic
classes on PUF for each drug reported
• NHANES 1999-2000:
six NDC therapeutic
classes on PUF for each drug reported
Coding Issues
Changes Over Time
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Approved indications for drugs change
over time (added or subtracted)
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“Major” uses for drugs with multiple
therapeutic uses change over time
•
Drugs may be replaced by other similar
drugs
•
Codes and categories are periodically
revised
•
Codes do not reflect “off-label” use
Coding Issues
Changes Over Time
• Because therapeutic indications
change over time
Analysts can merge the most current
classifications to drug data from previous years
Otherwise drugs may be classified differently
in different data years
This is less of an issue when analyzing
specific drugs
Drugs Prescribed, Administered or Provided
During Physician Office or OPD Visits, by NDC
Therapeutic Drug Class, 1995-96 and 2001-02
1995-96
2001-02
penicillins
thyroid
ACE inhibitors
acid/peptic disorders
antihistamines
antidepressants
0
5
10
15
20
drugs per 100 persons
25
SOURCE: Centers for Disease Control and Prevention, National Center for Health Statistics, National
Ambulatory Medical Care Survey and National Hospital Ambulatory Medical Care Survey.
Coding Issues
Multiple Therapeutic Indications
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Do you allow drugs with multiple approved
indications to be double counted?
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Example:
Aspirin has multiple therapeutic uses.
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More of an issue when comparing or
ranking categories than for analyses within
a given therapeutic category
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Coding Issues
Drugs with Overlapping Classifications in
FDA NDC Therapeutic Classes
Aspirin:
• Toradol
 1724 Antiarthritics
 1722 Non-Narcotic analgesics
 1728 Antipyretics
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Acetaminophen
 1722 Non-Narcotic Analgesics
 1728 Antipyretics
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Ibuprofen
 1724 Antiarthritics
 1722 Non-Narcotic Analgesics
 1727 NSAID
 1720 General Analgesics
 1722 Non-Narcotic
Analgesics
 1727 NSAID
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Celebrex
 1724 Antiarthritics
 1727 NSAID
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Meloxicam
 1724 Antiarthritics
 1727 NSAID
Antidepressant Use in N/HAMCS and
NHANES
Percent of population
visits per 100 population
Female
Female
Male
Male
N/HAMCS 2001-02
NHANES 1999-2999
N/NAMCS 1995-96
0
10
20
30
NHANES 1988-94
40
0
5
10
Sources: National Health and Nutrition Examination Surveys, National Ambulatory Medical Care Surveys and
National Hospital Ambulatory Medical Care Surveys
15
Cholesterol Drugs Prescribed, Administered Or
Provided During Physician Office And Outpatient
Department Visits, By Age Group: United States,
1995-2001
120
Statin only
100
Other anticholesterol drugs
80
80 years and over
60
65-79 years
40
40-54 years
20
0
1995-96
1997-98
1999-2000
2001
65-79 years
SOURCE: Centers for Disease Control and Prevention, National Center for Health Statistics, National
Ambulatory Medical Care Survey and National Hospital Ambulatory Medical Care Survey.
Coming Soon…..
Watch for Health, United States, 2004, with
Special Feature on Drugs!
• Overall use
• Asthma drugs
• Psychotherapeutic drugs used by
• Antidepressant use by adults
• Anti-cholesterol drugs
• NSAIDs
children
Prescription Drug Use in Past Month,
by Race and Ethnicity, 1999-2000
No drugs
3 or more
drugs
0
Mexican
20
40
Black non-Hispanic
60
80
White non-Hispanic
Source: Centers for Disease Prevention and Control, National Center for Health
Statistics, National Health and Nutrition Examination Survey
Percent of Asthma Visits with Long-Term
Control Drugs Prescribed, Ordered or
Provided, 1995-2002
60
55
50
45
40
35
30
1995-96
1997-98
1999-2000
2001-02
Percent of asthma visits
SOURCE: Centers for Disease Control and Prevention, National Center for Health Statistics,
National Ambulatory Medical Care Survey and National Hospital Ambulatory Medical Care Survey.