1 EPI235: Epi Methods in HSR April 24, 2007 L7 Program Evaluation with Longitudinal Data 3: Two case studies (Dr. Schneeweiss) Dr. Schneeweiss will illustrate a time series approach to evaluate health care cost-containment programs with longitudinal claims databases using the example of a Reference Drug Program in British Columbia. Using a formulary restriction for respiratory drugs he will illustrate the design and analytic issues of a randomized versus an observational analysis based on longitudinal data. Background reading: •Schneeweiss S, Walker AM, Glynn RJ, Maclure M, Dormuth C, Soumerai SB: Outcomes of reference drug pricing for angiotensin-converting enzyme inhibitors in British Columbia, Canada. N Engl J Med, 2002; 346:822- 829. •Schneeweiss S, Maclure M, Carleton BC, Glynn RJ, Avorn J. Clinical and
Transcript
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EPI235: Epi Methods in HSR
April 24, 2007 L7
Program Evaluation with Longitudinal Data 3: Two case studies (Dr. Schneeweiss)
Dr. Schneeweiss will illustrate a time series approach to evaluate health care cost-containment programs with longitudinal claims databases using the example of a Reference Drug Program in British Columbia. Using a formulary restriction for respiratory drugs he will illustrate the design and analytic issues of a randomized versus an observational analysis based on longitudinal data.
Background reading: •Schneeweiss S, Walker AM, Glynn RJ, Maclure M, Dormuth C, Soumerai SB: Outcomes of reference drug pricing for angiotensin-converting enzyme inhibitors in British Columbia, Canada. N Engl J Med, 2002; 346:822-829.•Schneeweiss S, Maclure M, Carleton BC, Glynn RJ, Avorn J. Clinical and economic consequences of a reimbursement restriction of nebulised respiratory therapy in adults: direct comparison of randomised and observational evaluations. Br Med J 2004;328:560-4.
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Case Study 1
Evaluating a Reference Drug Program
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Reference Drug Pricing in British Columbia
Reference price
(dhp CCBs: $31 per 30 days supply)
Paid by drug benefits program
Out-of-pocket contribution
Total drug price
Better name: Therapeutic MAC (maximum allowable cost)
$0
$31
$50
RP is not a pricing policy but a
reimbursement policy
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Reference Pricing in British Columbia
RP for ACEI also in 1997 Captopril, Quinapril, and Ramipril fully covered Enalapril required cost-sharing by patients
RP for dhp-CCBs in 1997 Felodipine fully covered Nifedipine, amlodipine, nicardipine required cost-
sharing by patients
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RP in BC and other jurisdictions?
Reference Pricing was suggested to contain cost for a Medicare drug benefits program.Huskamp HA, Rosenthal MB, Frank RG, Newhouse JP. Health Affairs 2000;19:8-23.
Kanavos P, Reinhardt U. Health Affairs 2003;22(3).
Germany was the first jurisdiction with RP. However, there were no evaluations of clinical consequences and net savings.Schneeweiss S, Schoffski O, Selke GW. Health Policy 1998;44(3):253-60.
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Study PopulationAll residents of British Columbia >65 covered by
Pharmacare plan A, the state wide pharmaceutical benefits program (1/2 million).
Results: 6) At least $2.9 million net savings in the first 6 months
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Patient spending ($)Total drug spending ($)
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PPI restrictionFair PharmaCare†
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Slide 8
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Methods: PPI utilization data
Individual level data from all British Columbia seniors
LinkingAll pharmacy dispensings
(PharmaNet)Medical services, hospitalizations, and
vital statsMain outcome variable:
GI complications (power to show +-24 cases/m)
Drug spending (plan and patients)Time trend analyses are least prone to biasSlide 9
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Background: Therapeutic substitution
Logic extension of generic substitution Is based on therapeutic equivalence of drugs
in groupPPIs ideal examples because very
homogeneous group of drugsSimilar policies: Reference Drug Programs
RDP for ACE, CCB, nitrates, and NSAIDs in British Columbia
Slide 10
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Background: Implementation IssuesNeed to be careful establishing therapeutic
equivalenceWorks only if several alternatives are
availableWorks best if preferred drug is a lot less
costlySingle drug markets:
Combine with PA programs Aim to ensure that patients with specific indications
receive drugs
Slide 11
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Summary & Questions
Substantial and rapid change in utilizationNo increase in discontinuationsNo increase in adverse GI outcomesSubstantial savingsHomogeneous groups like PPI are idealCareful expansion to more groups
Slide 12
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Case Study 3
Randomized policy trial vs. quasi-experimental time trend analyses
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… or randomization?
Time
Intervention
Intervention group
Control group
R
Assumptions for causal inference:
1. Subjects comply with their assigned ‘treatment’ = policy
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Research question
Will we observe the same effects of a formulary restriction using A) a randomized trial design vs. B) a state-of-the-art observational design
recommended and used by policy evaluation researchers? Soumerai et al. Milbank, 1993
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Case study: A Formulary restriction for nebulized respiratory drugs
Nebulized drugs were no longer covered by PharmaCare, B.C., after March 1,1999 but were fully covered before
10% of physicians were randomized to be exempted from the restriction for 6 months
(=randomized controls)10% of physicians who were subject to the
restriction were matched by location and volume (=intervention group)
Schneeweiss, BMJ under review
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Figure 1: Pairs of smaller more remote communities from which one was randomly selected to be a control
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Figure 2: A pair of urban physician addresses (marked +) from which one was randomly selected to be a control
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EvaluationStudy subjects
Patients with at least 2 nebulizer dispensings from same study physician before the formulary restriction
386 control patients; 449 intervention patients
Longitudinal claims data for entire province: Rate of physician visits Rate of ER hospitalizations $$ for nebulized drugs $$ for inhalers
Outcome measures
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Design
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Randomized analysis
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Control group
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Observational analysis:4,625 patients not involved in randomized design
Historical controls
Intervention group
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Randomized analysis: 60% of control patient were non-compliant!
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Physician visit rate
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ER hospitalization rate
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Key results
Outcomes per month
Randomized analysis
Observational analysis
Corrected for non-
compliance
$$ for nebulizer -$8.2 -$24 ** -$21 1
$$ for inhaler $1.1 $2.8 **
ER hospitalization
-0.4/100 0.4/100
Visits 6.2/100 2.6/100
** p < 0.0001 (bootstrap estimate) 1 Zelen, Biometrics 1991
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CON (n=140) TRT (n=147)
Mea
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Q s
core Before After
Figure 7: Comparison of Treatment and Control Group Quality of Life
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Weighing the benefits of randomized and non-randomized drug policy research
Randomization Observation
Upfront investment for planning and implementation
