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Predictors of Low Clopidogrel Adherence Following PercutaneousCoronary Intervention

Paul Muntner, PhDa,*, Devin M. Mann, MDb, Mark Woodward, PhDc, James W. Choi, MDd,Robert C. Stoler, MDd, Daichi Shimbo, MDe, Michael E. Farkouh, MDf,g, and Michael C. Kim, MDf

Few data are available on factors associated with low adherence or early clopidogreldiscontinuation after percutaneous coronary intervention (PCI). Patients (n � 284) wereevaluated before hospital discharge after PCI to identify factors associated with lowadherence to clopidogrel 30 days later. Adherence to daily medications before PCI wasassessed using the 8-item Morisky Medication Adherence Scale (MMAS-8) and categorizedas low (score <6), medium (score 6 to <8), or high (score 8). Low adherence to clopidogrelwas defined as MMAS-8 score <6 (n � 21) or having discontinued clopidogrel (n � 11),which was ascertained during a 30-day interview after PCI. At 30 days after PCI, 11% ofpatients had low adherence to clopidogrel. Odds ratios (95% confidence intervals [CIs]) forlow adherence to clopidogrel were 3.78 (1.09 to 13.1), 3.06 (1.36 to 6.87), 2.46 (0.97 to 6.27),and 3.36 (0.99 to 11.4) for patients who before PCI reported taking smaller doses ofmedication because of cost, had difficulty filling prescriptions, had difficulty reaching theirprimary physician, and were not comfortable asking their doctor for instructions, respec-tively. Odds ratios (95% CIs) for low clopidogrel adherence after PCI in patients withmedium and low versus high adherence to daily medications before PCI were 6.13 (1.34 to28.2) and 10.9 (2.46 to 48.7), respectively. The c-statistic associated with MMAS-8 scoresbefore PCI for discriminating low clopidogrel adherence at 30 days after PCI was 0.733(95% CI 0.650 to 0.852). In conclusion, adherence to daily medications before PCI may bea useful indicator for identifying patients who will have low clopidogrel adherence after

PCI. © 2011 Elsevier Inc. All rights reserved. (Am J Cardiol 2011;108:822–827)

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Dual antiplatelet therapy with aspirin and clopidogrel isstandard of care for patients after percutaneous coronaryinterventions (PCIs).1 Despite the importance of persistenceo clopidogrel after PCI, little is known about factors asso-iated with low adherence and early discontinuation oflopidogrel. Therefore, we conducted an analysis of datarom the Ambulatory Closure Device Percutaneous Coro-ary Intervention (ABCD-PCI) trial to assess factors, col-ected before hospital discharge after PCI, associated witharly clopidogrel discontinuation or low adherence to clopi-ogrel at 30 days after PCI.

ethods

The ABCD-PCI trial included patients undergoing elec-ive PCI and was designed to confirm the safety of same-day

aDepartment of Epidemiology and Medicine, University of Alabama atBirmingham, Birmingham, Alabama; bSection of Preventive Medicine and

pidemiology, Boston University, Boston, Massachusetts; cThe Georgenstitute, University of Sydney, Sydney, Australia; dBaylor Heart and

Vascular Hospital, Baylor University Medical Center, Dallas, Texas; eDe-artment of Medicine, Columbia University, New York, New York; fZena

and Michael A Wiener Cardiovascular Institute and Marie-Josèe and HenryR. Kravis Center for Cardiovascular Health, Mount Sinai School of Med-icine, New York, New York; gPeter Munk Cardiac Centre and Li Ka ShingKnowledge Institute, University of Toronto, Toronto, Ontario, Canada.Manuscript received March 2, 2011; revised manuscript received andaccepted April 27, 2011.

*Corresponding author: Tel: 205-975-8077; fax: 205-934-8665.

uE-mail address: pmuntner@uab.edu (P. Muntner).

0002-9149/11/$ – see front matter © 2011 Elsevier Inc. All rights reserved.doi:10.1016/j.amjcard.2011.04.034

ospital discharge after PCI. In addition, patients’ prefer-nce for same-day hospital discharge versus longer staysas evaluated. Patients were recruited from Mount Sinaiospital (New York, New York) and Baylor Heart andascular Hospital, Baylor University Medical Center (Dal-

as, Texas). Major inclusion criteria were age �75 years,aving type A or B lesions, and use of a closure device.atients with evidence of a recent acute coronary syndromer who received �3 stents were not enrolled. Overall 298atients were enrolled and completed baseline and fol-ow-up ABCD-PCI study visits. Patients who did not com-lete the medication adherence screening tool (n � 14),escribed later, at the 2 administrations were excluded. Thistudy was approved by the institutional review boards ofount Sinai School of Medicine and Baylor Universityedical Center. Patient consent for was obtained before

nrollment.Of relevance to the present analysis, data were collected

fter PCI but before hospital discharge using a self-admin-stered questionnaire and at 30 days after PCI using annterview administered questionnaire. The prehospital dis-harge survey instrument included domains assessing so-iodemographics, cigarette smoking, health insurancetatus, barriers to filling medications, patient–physicianommunication, beliefs about medication, and adherence toaily medications. Potential barriers to filling medicationsncluded skipping or taking smaller medication doses be-ause of cost and lack of health insurance coverage forrescription medications. Medication beliefs were assessed

sing the 16-item Beliefs about Medicines Question-

www.ajconline.org

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823Coronary Artery Disease/Predictors of Low Clopidogrel Adherence

naire.2–5 Adherence to daily medications before PCI wasssessed using the 8-item Morisky Medication Adherencecale (MMAS-8).6 Items on this scale reflect reasons for

nonadherent behavior (e.g., forgetfulness, health beliefs,and side effects) and thus may be useful in identifyingunderlying causes of nonadherence. The MMAS-8 contains7 “yes” or “no” responses and 1 item scored on a 5-pointLikert-type scale. Scores on the MMAS-8 can range from 0to 8, with scores �6, 6 to �8, and 8 reflecting low, medium,and high adherence, respectively.6 The MMAS-8 has beenetermined to be reliable and associated with blood pressureontrol and pharmacy fill rates in subjects with hyperten-ion.6–8 For administration before hospital discharge, the

MMAS-8 was tailored to assess adherence to all medica-tions taken daily.

At 30 days after PCI, a separate questionnaire was ad-ministered by telephone by a trained research staff member.The 30-day follow-up questionnaire included an item aboutdiscontinuing clopidogrel. In patients who reported they didnot discontinue clopidogrel, the MMAS-8 was adminis-tered. For administration during the 30-day follow-up inter-view, the MMAS-8 was tailored to apply to clopidogreladherence. For example, the question “Do you sometimesforget to take your medications” was changed to “Do yousometimes forget to take your Plavix?” The outcome for the

Table 1Characteristics of study population by medication adherence before percu

Variable Overall(n � 284)

L(n

Age (years), mean � SD 55.8 � 7.9 54.9Women 26.2% 28Ethnicity

Non-Hispanic white 33.0% 30Non-Hispanic black 14.9% 15Hispanic 25.5% 22Asian 21.3% 23Other 5.3% 7id not graduate from high school 26.9% 30arried 68.7% 65

ncome �$20,000 34.8% 37elf-rated health, fair to poor 37.1% 44urrent smoker 15.0% 18kipped doses because of cost,

sometimes or often7.9% 14

maller doses because of cost,sometimes or often

4.7% 11

rescriptions covered by any healthinsurance

97.8% 97

ifficulty filling prescriptions,sometimes or often

16.9% 28

ifficult reaching primary doctor 11.6% 15omfortable asking doctor for

instructions95.0% 92

eeling that medicine is a necessity† 47.2% 53eeling that medicine is a concern† 48.9% 59eceived drug-eluting stent 79.9% 73

* Determined before hospital discharge after percutaneous coronary int† Feelings of necessity and concern were determined using the Beliefs

present analysis was discontinuation of clopidogrel and low

adherence to clopidogrel 30 days after PCI. Because of themoderate sample of the present study, discontinuation ofclopidogrel and low adherence to clopidogrel at 30 daysafter PCI were used as a pooled outcome, hereafter referredto as “low adherence.” Discontinuation at 30 days after PCIwas assessed by self-report and low adherence was defined

20% 12%

31%

23%

18%

49%65%

80%

2%0%

20%

40%

60%

80%

100%

Low (n=92) Medium (n=100) High (n=92)

HighMediumLow

Baseline Adherence

Dis

trib

utio

n of

Clo

pido

grel

Adh

eren

ce,

30 d

ays

follo

win

g PC

I

Figure 1. Distribution of clopidogrel adherence at 30 days after percuta-neous coronary intervention in patients with low (black bars), medium(gray bars), and high (white bars) adherence to daily medications beforepercutaneous coronary intervention.

coronary intervention

Adherence Before PCI* P Value for Trend

Medium High(n � 100) (n � 92)

56.2 � 8.1 56.5 � 7.6 0.3426.0% 24.2% 0.53

0.1529.6% 39.1%16.3% 13.0%28.6% 25.0%21.4% 18.5%4.1% 4.4%

28.6% 21.7% 0.1969.0% 71.7% 0.3437.4% 29.6% 0.3140.4% 26.1% 0.0115.3% 11.0% 0.158.1% 1.1% �0.001

3.0% 0.0% �0.001

96.9% 98.9% 0.60

17.2% 5.6% �0.001

12.2% 6.7% 0.0696.0% 96.6% 0.17

47.0% 41.3% 0.1055.0% 31.5% 0.00181.0% 84.6% 0.102

n using the 8-item Morisky Medication Adherence Scale.edication Questionnaire.8

taneous

ow� 92)

� 7.8.3%

.4%

.2%

.8%

.9%

.6%

.3%

.2%

.2%

.6%

.7%

.6%

.2%

.8%

.1%

.7%

.1%

.3%

.8%

.9%

erventio

as scores �6 on the MMAS-8.

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824 The American Journal of Cardiology (www.ajconline.org)

Characteristics of patients were calculated overall and bylevel of medication adherence (low, medium, and high)before PCI. Prevalence and odds ratios of low adherence toclopidogrel at 30 days after PCI were calculated for eachitem on prehospital discharge MMAS-8 administration.Distribution of adherence to clopidogrel (low, medium, andhigh) at 30 days after PCI was calculated by level of ad-herence to daily medications before PCI. Odds ratios forlow adherence at 30 days after PCI were calculated forpatient sociodemographics, medication-taking behaviors,beliefs about medications, and overall MMAS-8 scores as-sessed before hospital discharge after PCI. To assess howwell factors assessed before hospital discharge after PCIdiscriminate between those who subsequently had versusdid not have low clopidogrel adherence, c-statistics werecalculated for variables associated (p �0.10) with lowclopidogrel adherence in univariable analysis. In addition,

Table 2Odds ratios for having low adherence to clopidogrel at 30 days after percbefore percutaneous coronary intervention

Baseline Medication Adherence Scale Item L3

Sometimes forget to take medicineNoYes

Missed taking medicine in previous 2 weeks†

NoYesut back or stopped taking medication because felt

worse‡

NoYes

Sometimes forget to bring medication when leaving homeNoYes

Took all medicines on previous day†

NoYes

Sometimes stop taking medication because feel problemsare under control

NoYes

Ever feel hassled about sticking to treatment planNoYes

Have difficulty remembering to take all medicationsRarely/neverOnce in a whileSometimesUsuallyAlways

Baseline medication adherence scale category§

HighMediumLow

* Low adherence was defined as scores �6 on the 8-item Morisky Me† With the exception of medicines not taken as instructed by a physicia‡ Without telling their doctor.§ Determined before hospital discharge after percutaneous coronary inte

c-statistics were calculated for each item and for overall

scores on prehospital discharge administration of theMMAS-8. Because patients who receive drug-eluting stents(DESs) are recommended long-term clopidogrel therapy,for a sensitivity analysis odds ratios and c-statistics for lowadherence to clopidogrel at 30 days after PCI were calcu-lated and restricted to patients who received a DES. Allanalyses were conducted using SAS 9.2 (SAS Institute,Cary, North Carolina).

Results

Mean age of patients included in this analysis was 55.8years; 26% were women; and 33%, 15%, 26%, and 21%were non-Hispanic white, non-Hispanic black, Hispanic,and Asian, respectively (Table 1). Overall, before hospi-tal discharge after PCI, 32%, 35%, and 32% of patientsreported low, medium, and high adherence to daily med-

s coronary intervention associated with adherence to daily medications

herence atAfter PCI*

32)

Odds Ratio (95% CI) forLow Adherence at 30

Days After PCI

P Value

.1% 1 (reference) 0.004

.8% 3.03 (1.43–6.43)

.7% 1 (reference) �0.001

.0% 4.67 (2.13–10.2)

.4% 1 (reference) 0.239

.9% 1.63 (0.66–4.03)

.4% 1 (reference) 0.036

.0% 2.41 (1.06–5.47)

.0% 1 (reference) 0.662

.9% 0.82 (0.33–2.01)

.0% 1 (reference) 0.088

.0% 2.24 (0.89–5.65)

.0% 1 (reference) 0.066

.7% 2.02 (0.95–4.29)

.1% 1 (reference)

.6% 3.59 (1.49–8.63) 0.004

.0% 8.81 (3.23–24.0) �0.001

.0% N/A N/A

.0% N/A N/A

.2% 1 (reference)

.0% 6.13 (1.34–28.20) 0.002

.6% 10.9 (2.46–48.7) 0.02

Adherence Scale or having discontinued clopidogrel.se of percutaneous coronary intervention.

n using the 8-item Morisky Medication Adherence Scale.

utaneou

ow Ad0 Days

(n �

718

728

1015

920

1310

1020

916

6183600

21219

dicationn becau

ications, respectively. Also, 73.9%, 81.0%, and 84.6% of

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825Coronary Artery Disease/Predictors of Low Clopidogrel Adherence

participants with low, medium, and high adherenceto daily medications before PCI received DESs

Table 3Odds ratios for having low adherence to clopidogrel at 30 days afterpercutaneous coronary intervention associated with sociodemographicand medication-related characteristics assessed before hospital dischargefor percutaneous coronary intervention

Characteristic* Odds Ratio (95% CI) P Value

Age (years)�50 1 (reference)50–54 0.72 (0.24–2.16) 0.5655–59 0.78 (0.27–2.24) 0.64�60 0.67 (0.26–1.76) 0.42

Female vs male gender 1.33 (0.60–2.96) 0.49Race†

Non-Hispanic white 1 (reference)Non-Hispanic black 1.76 (0.63–4.91) 0.28Hispanic 1.10 (0.42–2.89) 0.84Asian 0.98 (0.34–2.80) 0.97

Did not vs did graduate fromhigh school

1.07 (0.47–2.44) 0.87

Married vs not married 0.73 (0.34–1.58) 0.43Income �$20,000 vs

�$20,0001.61 (0.74–3.53) 0.23

Overall health, fair or poor vsexcellent, very good, orgood

1.82 (0.87–3.81) 0.11

Current vs never/formercigarette smoker

0.79 (0.26–2.38) 0.67

Skipped doses because of cost,sometimes or often vsrarely, 1 time, or never

1.82 (0.57–5.75) 0.31

Took smaller doses because ofcost, sometimes or oftenvs rarely, 1 times, ornever

3.78 (1.09–13.07) 0.04

Prescriptions covered by anyhealth insurance, yes vsno

0.62 (0.07–5.49) 0.67

Have difficulty fillingprescriptions, sometimesor often vs rarely, 1 times,or never

3.06 (1.36–6.87) 0.007

Difficult to reach primarydoctor, yes vs no

2.46 (0.97–6.27) 0.06

Not comfortable vscomfortable asking doctorto explain instructions

3.06 (0.99–11.4) 0.05

Side effects from clopidogrel,yes vs no

1.07 (0.23–4.96) 0.93

Feeling that medicine is anecessity‡

1.14 (0.54–2.37) 0.74

eeling that medicine is aconcern‡

1.86 (0.87–3.97) 0.11

* Characteristics were assessed at baseline (before hospital dischargefter percutaneous coronary intervention).

† Patients with an “other” race were excluded from odds ratio analysis onrace because of the small sample.

‡ Feelings of necessity and concern were determined from a series ofquestions designed to gauge patients’ feelings about their medicines. Eachquestion was scored and then dichotomized into high and low feelings ofnecessity or concern depending on the question.

(p � 0.102).

Overall 32 patients (11%), 68 patients (24%), and 184patients (65%) had low, medium, and high adherence toclopidogrel at 30 days after PCI. Of those with low adher-ence, 11 (34%) had discontinued clopidogrel and 21 (66%)had a low MMAS-8 score. Of those with low adherence todaily medications before PCI, 20% had low adherence toclopidogrel in the month after PCI (Figure 1). In contrast,12% and 2% of those with medium and high adherence todaily medications before PCI had low adherence to clopi-dogrel at 30 days after PCI (p �0.001). Also, 49%, 65%,and 80% of patients with low, medium, and high adherenceto daily medications before PCI had high adherence toclopidogrel after PCI (p �0.001).

Four of the 8 items that comprise the MMAS-8 (some-times forgetting to take medications, missed taking medi-cation in previous 2 weeks, sometimes forgetting to bringmedications when leaving home, and having difficulty re-membering to take all medications), assessed for daily med-ication use before PCI, were associated with higher oddsratios for low adherence to clopidogrel at 30 days after PCI(Table 2). Odds ratios for low adherence to clopidogrel at 30days after PCI were 6.13 (95% confidence interval [CI] 1.34to 28.2) and 10.9 (95% CI 2.46 to 48.7) for patients withmedium and low adherence to daily medications before

Table 4C-statistics for discriminating low adherence to clopidogrel at 30 daysafter percutaneous coronary intervention for items assessed beforehospital discharge

Variable c-Statistic (95% CI)

Items associated (p �0.10) with lowclopidogrel adherence at 30 days afterpercutaneous coronary intervention(Table 3)

Smaller doses taken 0.611 (0.500–0.722)Difficulty filling prescriptions 0.627 (0.515–0.739)Difficulty reaching primary doctor 0.608 (0.497–0.719)Comfortable asking doctor 0.617 (0.506–0.729)

8-item Morisky Medication Adherence Scaleitems assessed at baseline

Sometimes forget to take medicine 0.684 (0.592–0.776)Missed taking medicine in previous 2

weeks0.701 (0.601–0.801)

Ever cut back or stopped taking medicationbecause felt worse

0.564 (0.453–0.675)

Sometimes forget to bring medication whenleaving home

0.639 (0.528–0.749)

Took all medicines on previous day 0.570 (0.454–0.686)Sometimes stop taking medication because

feel problems are under control0.629 (0.527–0.732)

Ever feel hassled about sticking totreatment plan

0.627 (0.528–0.726)

Have difficulty remembering to take allmedications

0.749 (0.660–0.839)

Overall 8-item Morisky MedicationAdherence Scale score at baseline

Baseline 8-item Morisky MedicationAdherence Scale adherence score

0.733 (0.650–0.815)

All variables were assessed at baseline, i.e., before hospital dischargeafter percutaneous coronary intervention.

PCI, respectively.

Mtati

siFpdacP

Irisdcbtlnl

826 The American Journal of Cardiology (www.ajconline.org)

Odds ratios for low adherence to clopidogrel after PCIassociated with patient characteristics and behaviors arepresented in Table 3. Of note, odds ratios for low adherenceto clopidogrel were 3.78 (95% CI 1.09 to 13.1) for patientswho before PCI reported sometimes or often taking smallerdoses because of cost, 3.06 (95% CI 1.36 to 6.87) forpatients who reported sometimes or often having difficultyfilling prescriptions, 2.46 (95% CI 0.97 to 6.27) for patientswho had difficulty reaching their doctor, and 3.36 (95% CI0.99 to 11.4) for patients who were not comfortable askingtheir doctor for instructions.

C-statistics for discriminating low adherence to clopi-dogrel 30 days after PCI associated with items assessedbefore hospital discharge after PCI are presented in Table 4.C-statistics were �0.65 for 3 items on the predischargeMMAS-8 administration (sometimes forgetting to takemedications, missing taking medicine in previous 2 weeks,and having difficulty remembering to take all medication)but none of the other variables evaluated. The c-statistic forthe MMAS-8 administered before PCI was 0.733 (95% CI0.650 to 0.815).

Twenty-four of the 226 patients (10.6%) receivingDESs had low adherence to clopidogrel 30 days afterPCI. Of patients who received DESs, odds ratios for lowclopidogrel adherence were 2.47 (95% CI 0.46 to 13.1)and 13.2 (95% CI 2.77 to 56.5) for patients with mediumand low adherence versus high adherence to daily med-ications before PCI. The c-statistic for discriminating lowadherence to clopidogrel at 30 days after PCI associatedwith MMAS-8 scores assessing adherence before PCIwas 0.771 (95% CI 0.663 to 0.879).

Discussion

In the present study, several patient, provider, and healthsystem factors were associated with adherence to clopi-dogrel after PCI. Of note, a strong graded association waspresent between level of adherence to daily medicationsbefore PCI and adherence to clopidogrel after PCI. OverallMMAS-8 score, assessed before hospital discharge for PCI,had a c-statistic �0.7 for discriminating between patientswho subsequently had and those who did not have lowadherence to clopidogrel after PCI. Other factors related tolow adherence to clopidogrel included cost issues, physicianand pharmacy access, and patient–provider communication.

Early discontinuation of clopidogrel after PCI is com-mon. Over 9 months of follow-up of participants undergo-ing PCI in the Clopidogrel in Unstable angina to preventRecurrent ischaemic Events (PCI-CURE), 9.7% discontin-ued clopidogrel.9 In the Prospective Registry Evaluating

yocardial Infarction: Event Recovery (PREMIER) regis-ry, 16% of patients were not taking clopidogrel 30 daysfter their PCI procedure.10 Early clopidogrel discontinua-ion has been associated with stent thrombosis after DESmplantation.11,12 Also, all-cause mortality rates at 1 year

after PCI were 7.5% and 0.7% for patients who had discon-tinued and were still taking clopidogrel therapy, respec-tively, at 30 days after PCI in the PREMIER registry (haz-ard ratio 9.02, 95% CI 1.3 to 60.6).10

A few previous studies, primarily secondary data analy-

ses, have examined factors associated with early clopidogrel

discontinuation. Patients in the PREMIER registry who hadstopped taking clopidogrel were older, less likely to bemarried and have completed high school, and more likely tohave avoided health care because of cost and have a historyof cardiovascular disease and anemia.10 Also, patients whodid not receive discharge instructions for medication usewere less likely to be taking clopidogrel. In a multivariableadjusted model, having less than a high school educationwas the only factor significantly associated with clopidogreldiscontinuation (odds ratio 1.79, 95% CI 1.01 to 3.10).Identifying key determinants of low adherence to and earlydiscontinuation of clopidogrel may aide in the developmentof interventions to increase adherence after PCI.

Several factors related to low clopidogrel adherence inthe present study have not been previously reported. Theseinclude low adherence to daily medications before PCI, costissues, pharmacy access, and patient–physician communi-cation. In the context of the physician–patient relation, poorcommunication has been shown to limit adherence to med-ication.13 The present study identified patient-level factors(e.g., forgetfulness), connection of patients with their healthcare providers (e.g., not feeling comfortable asking theirdoctors questions), and health system factors (e.g., difficultyfilling prescriptions, cost issues) with low clopidogrel ad-herence.

Identifying patients who are likely to discontinue clopi-dogrel early or have low adherence can affect clinical de-cision making before PCI. Specifically, cardiologists maychoose to use bare metal stents or balloon angioplasty forpatients they identify as likely to discontinue or have lowadherence to clopidogrel after PCI. Previous studies havedocumented the inability of clinicians to intuitively assesspatients’ adherence to medication.14,15 The present studyuggests that it may be possible to use a few items todentify who is likely to discontinue clopidogrel after PCI.uture studies with larger samples and a longer follow-uperiod are needed to develop a screening tool for clopi-ogrel adherence after PCI using a standard psychometricpproach. In turn a short (e.g., �10 items) screening toolan be easily administered, scored, and interpreted beforeCI and may be useful for guiding clinical decisions.

The present analysis has several potential limitations.t was conducted using low-risk patients enrolled in aandomized controlled trial. The consistency of our find-ngs in high-risk patients (e.g., those with acute coronaryyndromes) needs to be evaluated. Follow-up for clopi-ogrel adherence was limited to 30 days after PCI andollection of outcomes data (e.g., stent thrombosis) waseyond the scope of this study. In addition, we assessed onlyhe relation between 1 adherence tool (i.e., the MMAS-8) andow adherence to clopidogrel after PCI. Future studies areeeded to determine if other published adherence scales predictow adherence to clopidogrel better than the MMAS-8.16,17

The small sample in this study required us to pool togetherdiscontinuation and low adherence to clopidogrel. The pres-ent study has several strengths including a high follow-uprate (96%), data collection using structured questionnairesand a validated medication adherence scale, and inclusion ofan ethnically diverse population. In the present study, wedocument a strong association between several patient fac-

tors and clopidogrel adherence after PCI. Studies are needed

1

827Coronary Artery Disease/Predictors of Low Clopidogrel Adherence

to confirm these findings and identify the optimal combina-tion of questions for predicting low clopidogrel adherenceafter PCI.

Acknowledgment: Use of the ©MMAS is protected byUnited States copyright laws. Permission for use is required.A license agreement is available from Donald E. Morisky,ScD, ScM, MSPH, Department of Community Health Sci-ences, UCLA School of Public Health, 650 Charles E.Young Drive South, Los Angeles, California 90095-1772.

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2. Horne R, Weinman J. Patients’ beliefs about prescribed medicines andtheir role in adherence to treatment in chronic physical illness. J Psy-chosom Res 1999;47:555–567.

3. Horne R, Weinman J, Hankins M. The beliefs about medicines question-naire: the development and evaluation of a new method for assessing thecognitive representation of medication. Psychol Health 1999;14:1–24.

4. Byrne M, Walsh J, Murphy AW. Secondary prevention of coronaryheart disease: patient beliefs and health-related behaviour. J Psycho-som Res 2005;58:403–415.

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7. Krousel-Wood M, Islam T, Webber LS, Re RN, Morisky DE, MuntnerP. New medication adherence scale versus pharmacy fill rates inseniors with hypertension. Am J Manag Care 2009;15:59–66.

8. Krousel-Wood MA, Muntner P, Islam T, Morisky DE, Webber LS.Barriers to and determinants of medication adherence in hypertensionmanagement: perspective of the cohort study of medication adherenceamong older adults. Med Clin North Am 2009;93:753–769.

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