Turning the Tide?
Medication Adherence
After Copayment
p y
Reductions
Matthew L. Maciejewski, PhD
Durham VA & Duke University
AcademyHealth ARM
Monday June 28, 2010
Acknowledgements

Collaborators
– Joel Farley,
Farley PhD RPh
RPh:: UNC
UNC--Chapel Hill
– Daryl Wansink, John Parker: BCBSNC

Funding
g
– RWJ Foundation HCFO Initiative
– BlueCross Blue Shield of NC
Distribution of Covered Workers Facing Different
Cost-Sharing for Rx Drug Benefits,
Benefits 2000-2009
27%
2000
2001*
2001
49%
41%
2002*
22%
41%
55%
‡
2004 3%
18%
30%
63%
2003*
13%
23%
65%
13%
20%
10%
2005* 4%
70%
15%
2006 5%
69%
16%
‡
2007
7%
2008*
7%
2009*
0%
68%
16%
70%
11%
10%
15%
67%
20%
30%
40%
12%
50%
*Distribution is statistically different from distribution for the previous year
shown (p<.05).
‡No statistical tests are conducted between 2003 and 2004 or between
2006 and 2007 due to the addition of a new category.
Note: Fourth
Fourth-tier
tier drug cost sharing information was not obtained prior to
2004.
Source: Kaiser/HRET Survey of Employer-Sponsored Health Benefits,
2000-2009.
60%
2%
70%
80%
8%
1%
1%
2%
1%
2%
2%
2%
6%
1%
3%
4%
1%
3%
3%
5%
8%
90%
100%
Four or More Tiers
Three Tiers
Two Tiers
Payment is the same regardless of type of drug
No cost sharing after deductible is met
Other
Medication Copay Trends for
Workers with 3+ Tiers, 20002000-2009
2000-2009 Kaiser/HRET Survey of Employer-Sponsored Health Benefits
Increased Out
Out--of
of--Pocket Costs
Reduce Medication Adherence
Goldman 2004 JAMA; figure from Chernew & Fendrick, 2009 SOA
Value-Based Insurance Design
Valueg as
Alternative to Increasing Copays

Link copayments to clinical effectiveness and
value
– Lower copays for cost
cost--saving/effective Rx

Limited
Li it d evidence
id
on VBID
– Simulations on Medicare enrollees found cost
saving (ACEIs if diabetes+HTN),
diabetes+HTN), cost
cost--effective
for p
post-AMI p
postpatients
– 2-5% annual improvement in adherence from 6
quasi--experimental studies of variable quality
quasi
– Ongoing trials
Rosen, 2005 Ann Int Med; Choudhry 2008 Circ; Chernew 2008 HA; AJMC papers
Policy
y Change
g &
Research Question

O 1/1/08,
On
1/1/08 llarge Southeastern
S th t
plan
l reduced
d
d
– Generic copays to $0 for enrollees of employers
who opted in
– BrandBrand-name copays from Tier 3 to Tier 2 for
enrollees in treatment and control employers
– PopulationPopulation-based VBID implementation (750k)

Did initiation of a VBID program impact
medication adherence?
– Expected change: ACEIs, betabeta-blockers, calcium
channel blockers, diuretics, oral agents, statins
– Expected
E pected no change:
change ARBs,
ARBs cholesterol
choleste ol
absorption inhibitors
Study
y Design
g and Data
 Study
Design
– Retrospective pre
pre--post design with non
non-equivalent cohort
– PrePre-period: Jan
Jan--Dec 2007
– Post
Post--period: JanJan-Dec 2008
 Insurer
claims data
– Adherence outcome: Annual MPR pooled
for generic and brandbrand-name medications
– Explanatory variables: Tx,
Tx, time, Tx
Tx*time
*time
– Covariates:
C
Demographics,
h
casemix,
casemix, Rx
Analysis
y

Outcome equation
MPRit=β0+β1·Tx
T i+β2·Post
P tt+β3·Tx
T i·Post
P tt+β4·Xi+εit

Estimation Approach
– GLM with
ith binary
bi
distribution,
di t ib ti
inverse
i
sq roott link
li k

Estimation Problem
– If covariates balanced btn
btn.. treatment & control
due to randomization (or luck), then unbiased β3
– In this analysis,
anal sis covariates
co a iates not balanced (so
propensity score with 11-toto-1 matching)
Control Group
p NonNon-Equivalence
q
(Diuretic Sample)
Unmatched Sample
N=24,433
Participants
NonParticipants
Standardized
Differences
Age in years
51.7
52.0
-4.4%
Male
45%
37%
16.2%
Comorbidity (ETG)
2.5
2.5
0.1%
Medication Count
8.5
7.9
15.6%
1+ Ninety Day Fills
14%
22%
-20.6%
Prescriptions filled
that were generic
75%
73%
3.0%
Unadjusted Trends in
Diuretic Adherence (MPR)
Difference-in-difference=3%
Adjusted Adherence Difference
Associated with VBID Program
Note: GLM iin unmatched
N
h d sample,
l controlling
lli for
f age, gender,
d Episode
E i d Risk
Ri k Groups,
G
count off
unique medications filled, generic dispensing rate, total copay, and whether an enrollee filled
one or more prescriptions with a 90-day supply.
Value of NonNon-Equivalent
Dependent Variables (ARBs, CAIs)
Note: GLM iin unmatched
N
h d sample,
l controlling
lli for
f age, gender,
d Episode
E i d Risk
Ri k Groups,
G
count off
unique medications filled, generic dispensing rate, total copay, and whether an enrollee filled
one or more prescriptions with a 90-day supply.
Improvement in Covariate
Balance After PS Matching
(Diuretic Sample)
Standardized Differences
Unmatched Sample
Matched Sample
Age in years
-4.4%
0.5%
Male
16.2%
1.3%
Comorbidity (ETG)
0.1%
1.1%
Medication Count
15.6%
-1.6%
Total Copay in Year
6.5%
3.9%
1+ Ninety Day Fills
-20.6%
20.6%
-0.6%
0.6%
Prescriptions filled
that were generic
3.0%
-5.2%
Total Sample
24,433
14,218
Adjusted Adherence Difference
Associated with VBID Program
Base Case
Matched No Covariates
Matched Covariates
4.5%
4 0%
4.0%
3.5%
3.0%
2.5%
2.0%
1.5%
1.0%
0.5%
0.0%
Note: Based on a generalized linear models, controlling for age, gender, Episode Risk Groups, count of
unique medications filled, generic dispensing rate, total copay, and whether an enrollee filled one or
more prescriptions with a 90-day supply.
How Comparable Are
VBID Results Across Studies?
6%
5%
Maciejewski
4%
Choudhry
Chernew
3%
Sedjo
Kelly
2%
Chang
Rodin
1%
Mahoney
0%
OHAs
ACEI
Beta block
Statin
Limitations

Limited covariate adjustment

No adjustment for unobserved confounding

May not generalize outside of SE U.S.
– However, results consistent with prior studies
Strengths
No disease management coco-intervention
 Study Design improves internal validity

– Pre
Pre--post comparison
– NonNon-equivalent control group whose equivalence
improved via propensity score
– NonNon-equivalent dependent vars (ARBs, CAIs)
 Adherence trends not expected to respond to VBID
unlike other medication classes

Sample size
– Large
g enough
g to evaluate 8 medication classes
because largest VBID implementation to date
Conclusion

VBID is being adopted widely, but concerns
of limited evidence due to weak designs
– We address major limitations of prior studies

VBID program associated with 22-4%
improvement
p
in adherence at one year
y
– Consistent with prior studies
– Clinical impact unknown

Payment reform and incentives hold promise
– Need longerlonger-term adherence & expenditure
trends to have solid business case for VBID
Cutler 2010 NEJM; IOM 2009 CER report
“…it is not possible to put right with statistics
what has been done
wrong by (study) design”
- Cook & Steiner 2010 Psych Methods
Questions?