Inappropriate clopidogrel adherence explains stent related adverse outcomes

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Inappropriate clopidogrel adherence explains
stent related adverse outcomes

• Leonardo Tamariz, MD, MPH
• University of Miami

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Antiplatelet use post-stent

• Angioscopic studies show lack of neo-intimal
  coverage and thrombi post-stent.
• Drug eluting stents have been associated to late
  MI.
• ACC/AHA/SCAI recommends in patients with low
  bleeding risk maintaining clopidogrel for 12
  months after a stent.
• Clopidogrel is now a chronic medication.

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Consequences of lack of medication adherence in
CV disease

• Inadequate disease control.
• Low adherence to beta-blockers or statins in post
  MI patients increases the death rate.
• Represents a significant burden to healthcare
  utilization the estimated yearly cost is 396
  to 792 million.
• One two thirds of all medication-related
  hospital admissions are attributed to
  nonadherence.

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Specific aims

• To evaluate clopidogrel medication adherence in a
  cohort of patients with stents.
• To evaluate if clopidogrel adherence affects
  stent related outcomes.

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Methods Data source
Humana EDW
Medical File ICD 9 codes
Member File Demographics Costs Provider
information
Pharmacy File GPI codes Dosage Refill patterns
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Methods Study design
Clopidogrel adherence
MI Death
Clopidogrel users (n5,838)
Stents (n7,091)
3.2 0.7 years
Non- clopidogrel users (n1,253)

• Inclusion criteria
• 18 years or older
• Procedure claim for bare metal stent (36.06) or
  drug eluting stent (36.07) between January 1,
  2003-June 1, 2005.

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Methods Clopidogrel adherence

• Clopidogrel use defined by Generic Product
  Identifiers (GPI code85158020)
• Adherence defined by medication possesion ratios
  (MPR).
• Appropriate adherence 80 or more MPR
• Innapropriate adherence

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Methods Outcomes

• Myocardial infarction
• ICD 9 code 410.x with a hospitalization
• Death (all cause mortality)
• Social security death index match
• Combined
• MI or death

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Methods CV risk factors (ICD-9 definitions)

• Diabetes (250.xx)
• Hypertension (401.xx, 402.xx, 403.xx,404.xx,405.xx
  )
• Abnormal lipid panel (272.xx),
• Obesity (278, 278.0, 278.00, 278.01, 278.1).

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Methods Statistical analysis

• Baseline characteristics with chi-square and
  t-test
• Predictors of innapropriate use with logistic
  regression
• Person-time and hazard ratios of events using Cox
  proportional adjusted for demographics, claims
  for CV risk factors, claims for heart failure,
  type of stent and MI at presentation.

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Results Baseline characteristics
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Results Distribution of MPRs
13
Results Predictors of inappropriate clopidogrel
use
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Results Incidence of MI by adherence to
clopidogrel
HR 1.35(1.08-1.70)p0.009
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Results Incidence of death by adherence to
clopidogrel
HR 1.32(1.12-1.55)p 16
Results Incidence of combined outcome by
adherence to clopidogrel
HR 1.31(1.11-1.54)p 17
Conclusions

• Twenty eight percent of clopidogrel users
  post-stent deployment are not adherent.
• Lack of adherence to clopidogrel post-stent
  increases the risk of myocardial infarction and
  death.

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Limitations

• Lack of validation of exposure and outcomes.
• Insured patient population, less burden of
  disease compared to other studies.
• Unable to document ASA use, coronary anatomy
  where stent was placed due to use of
  administrative claims.

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Clinical implications and unresolved issues

• We need to stress the importance of clopidogrel
  adherence after a stent.
• We need to inquire patients about clopidogrel
  adherence post-stent.
• We need to identify individual reasons for lack
  of clopidogrel adherence.
• Need a randomized trial to determine the efficacy
  of different interventions to improve clopidogrel
  adherence.