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

1. The Use of the World Health Organization’sDefined Daily Dose in Drug Cost & Utilization Analyses Elena Lungu Senior Economist 2008 CADTH Symposium Edmonton, Alberta April 29th, 2008

2. 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

3. 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)

4. Based on a review of the available information including doses used in various countries when this information is available Initial dose not captured (if different than maintenance) Average of two or more commonly used dose sizes Average of two or more commonly used dose sizes Ingredient & form Other indications not captured Children dose not captured, except in drugs prescribed only to children DDD Definition Assumedaveragemaintenance dose per day for a drug used for its main indication in adults ODB, 2005/06 + 95% TOTAL

5. Limitations Advantages DDD in Canadian Administrative Databases Valuable comparative measure of drug exposure Applicability in Policy Decisions Allows integration with other databases Applicability in Cost Analyses Readily available, inexpensive & easy to use Interpretation of Canadian Utilization Maintained & updated by WHO Integration in Canadian Administrative Databases

6. 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

7. 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

8. 99% 130% Higher Drug Exposure DDD – Interpretation of Canadian Utilization Example: Atorvastatin in ODB – DDD 10mg

9. 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

10. 99% -10% 4% 130% DDD – Applicability in Cost Analyses (Cont’d) Example: Atorvastatin in ODB – DDD 10mg

11. DDD – Applicability in Cost Analyses (Cont’d) 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

12. Therapeutic-Mix: Serum Lipid Reducing Agents Example: ODB – 2005/06 -23% 19%

13. 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

14. 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

15. Limitations Advantages 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

16. 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

17. Take away: What’s the best quantity measure? – It depends… • 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?