The Use of the World Health Organizations Defined Daily Dose in Drug Cost

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The Use of the World Health OrganizationsDefined
Daily Dose in Drug Cost Utilization Analyses

• Elena Lungu
• Senior Economist
• 2008 CADTH Symposium
• Edmonton, Alberta
• April 29th, 2008

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National Prescription Drug Utilization
Information SystemNPDUIS

• Established in September 2001 by F/P/T Ministers
  of Health
• Responsibilities of PMPRB established by the
  Minister of Health, pursuant to Section 90 of the
  Patent Act
• Purpose to facilitate informed administration of
  public drug plans in Canada by providing
• Timely, standardized and comparative prescription
  drug information from participating public drug
  plans in response the priorities identified by
  the F/P/T Steering Committee
• Critical analyses of price, utilization and cost
  trends
• Collaborative initiative between CIHI and the
  PMPRB

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Purpose of the Study

• Reliable quantity measures are the foundation of
  drug utilization studies
• There is a need to transform the physical units
  into treatment units
• The Defined Daily Dose (DDD) widely utilized by
  researchers
• As it converts the physical quantities into a
  standards unit of measure day
• NPDUIS has applied the DDD methodology to drug
  utilization studies gained a strong
  understanding of the advantages limitations to
  applying DDD in the context of Canadian
  administrative databases, identified
• Concerns regarding results interpretation that
  limit the applicability of DDD methodology
• The need to consider other quantity measures
  (e.g. the reported Day Supply)

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WHO ATC/DDD System Background

• The World Health Organization (WHO) developed
  maintains the Anatomical Therapeutic
  Chemical/Defined Daily Dose (ATC/DDD) system
• DDD assigned by WHO Collaborating Centre for Drug
  Statistics Methodology in collaboration with WHO
  International Working Group for Drug Statistic
  Methodology
• DDD Methodology transforms the physical
  quantities of drugs into a standard unit of
  measure
• DDD Purpose to serve as a tool for drug
  utilization research in order to improve quality
  of drug use
• ATC/DDD system widely utilized worldwide by
  researchers to report on drug utilization
  statistics

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DDD Definition
Assumed average maintenance dose per day for a
drug used for its main indication in adults
ODB, 2005/06
95
TOTAL
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DDD in Canadian Administrative Databases
Valuable comparative measure of drug exposure
Applicability in Policy Decisions
Allows integration with other databases
Applicability in Cost Analyses
Interpretation of Canadian Utilization
Readily available, inexpensive easy to use
Maintained updated by WHO
Integration in Canadian Administrative Databases
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DDD Integration in Canadian Admin. Databases

• Overwhelming majority of drug utilization is for
  drugs with ATC assigned
• Significant utilization for drugs without DDD
• 10 of Cost, 12 of Rx in NPDUIS Selected Public
  Plans NS, NB, MB SK
• d
• DDD methodology relies on reported units
• Canadian data may be reported in unit measure
  different than the ATC/DDD system Unit
  conversion required
• Even for the same DIN, the reported unit of
  measure may differ Unit standardization
  required
• Inaccurate unit reporting may occur

AdmR ATC/DDD system
Form Canadian Admin. Databases
link
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DDD Interpretation of Canadian Utilization

• Technical Drug Use Metric rarely if ever
  prescribed WHO
• May not be reflective of the avg. daily dose in
  Canada, due to differences in
• May not mirror the drug utilization of selected
  segments of population (demographic or
  therapeutic skewing)
• Purely a comparative measure of drug exposure
• DDD not appropriate in making assumptions on
  treatment lengths

• Reimbursement policies
• Prescribing practices
• Etc.

• Demographics
• Approved indications
• Disease prevalence

Apply ATC/DDD methodology interpret with caution
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DDD Interpretation of Canadian Utilization
Example Atorvastatin in ODB DDD 10mg
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DDD Applicability in Cost Analyses
It is usually not valid to use this metric to
compare costs of different drugs or drug
groups WHO

• DDD Misuses in Cost Analyses
• Simple average cost at DDD level across drugs
• Comparison of actual or difference in avg. cost
  at DDD level not appropriate
• Cost decomposition
• Contribution of individual effects distorted
• Cost per illness, cost-benefit,
  cost-effectiveness cost utility analyses
• Budget Impact Analyses

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DDD Applicability in Cost Analyses (Contd)
Example Atorvastatin in ODB DDD 10mg
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DDD Applicability in Cost Analyses (Contd)

• DDD in Cost Drivers Analysis
• Main ingredients Price Quantity
• If quantity expressed in DDDs, then
• Price Effect accurate if calculated at DIN level
• As it represents the price differential as
  opposed to actual price
• Volume Effect may be overstated or understated
• As it represents the drug exposure as opposed to
  actual treatment units
• Therapeutic-Mix may be inaccurate
• As it is based on average cost / DDD

Example
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Therapeutic-Mix Serum Lipid Reducing Agents
Example ODB 2005/06
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-23
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DDD Applicability in Policy Decision

• Misuses of ATC/DDD in Policy Decisions
• Cost analyses based on DDD methodology in support
  of policy decisions
• Determining therapeutic equivalence
• Reimbursement decisions
• Therapeutic group reference pricing decisions
  other pricing decisions
• Price comparisons

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Conclusions DDD Methodology

• A valuable comparative measure of drug exposure
• Regional (interprovincial, international, etc.)
  trend analyses
• Best applied to specific classes of drugs
• Comprehensive studies may not be all that
  comprehensive
• DDD may align better with actual daily dose in
  some classes/drugs than other
• Integration process may be eased
• Best applied at population level, as opposed to
  specific population segments
• DDD generally not appropriate in a broad array
  of Cost Analyses on multiple drugs
• Caution required when applying the DDD
  methodology in analyses in support of policy
  decisions

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Day Supply Information Fieldin Canadian
Administrative Databases
Difficult to interpret in non-daily treatments
Claim specific Actual drug utilization
Possible misreporting
Already integrated in some drug plan
administrative databases
Unavailable in some administrative databases
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Day Supply Information FieldPreliminary Quality
Investigation

• Scope
• 2005/06 fiscal year, NPDUIS selected drug plans
  PEI, NS, NB, ON NIHB
• Methods Avg. Daily Supply (Units/Days) Avg. Rx
  Length (Days/Rx)
• Results for the above scope
• Avg. Daily Supply at drug strength level
  comparable across plans
• Avg. Rx Length at plan level comparable across
  drugs
• Day Supply information field quality assurance
  is a prerequisite

• Agents Acting on Renin-Angiotensin System
• Serum Lipid Reducing Agents
• Drugs for Acid-Related Disorders
• Psychoanaleptics

Oral solids
Similar utilization patterns
Conclusion When available for specific classes
of drugs, Day Supply is a valuable information
field may be used in drug utilization cost
analyses
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Take away
It depends
Whats the best quantity measure?

• Understand the research question its scope
• Know the data availability quality
• Know the advantages limitations of the
  available quantity measures given the context
• Decide on the most appropriate quantity measure
  to report on
• Recognize that these quantity measures may
  capture partial drug utilization (unavailable
  DDD, unreliable Day Supply, etc.)

If the actual daily dose were to differ than the
DDD, would the findings change?