Few data are available on factors associated with low adherence or early clopidogrel discontinuation after percutaneous coronary intervention (PCI). Patients (n = 284) were evaluated before hospital discharge after PCI to identify factors associated with low adherence to clopidogrel 30 days later. Adherence to daily medications before PCI was assessed using the 8-item Morisky Medication Adherence Scale (MMAS-8) and categorized as low (score <6), medium (score 6 to <8), or high (score 8). Low adherence to clopidogrel was 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% of patients had low adherence to clopidogrel. Odds ratios (95% confidence intervals [CIs]) for low 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 of medication because of cost, had difficulty filling prescriptions, had difficulty reaching their primary physician, and were not comfortable asking their doctor for instructions, respectively. Odds ratios (95% CIs) for low clopidogrel adherence after PCI in patients with medium and low versus high adherence to daily medications before PCI were 6.13 (1.34 to 28.2) and 10.9 (2.46 to 48.7), respectively. The c-statistic associated with MMAS-8 scores before 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 be a useful indicator for identifying patients who will have low clopidogrel adherence after PCI.
Dual antiplatelet therapy with aspirin and clopidogrel is standard of care for patients after percutaneous coronary interventions (PCIs). Despite the importance of persistence to clopidogrel after PCI, little is known about factors associated with low adherence and early discontinuation of clopidogrel. Therefore, we conducted an analysis of data from the Ambulatory Closure Device Percutaneous Coronary Intervention (ABCD-PCI) trial to assess factors, collected before hospital discharge after PCI, associated with early clopidogrel discontinuation or low adherence to clopidogrel at 30 days after PCI.
Methods
The ABCD-PCI trial included patients undergoing elective PCI and was designed to confirm the safety of same-day hospital discharge after PCI. In addition, patients’ preference for same-day hospital discharge versus longer stays was evaluated. Patients were recruited from Mount Sinai Hospital (New York, New York) and Baylor Heart and Vascular Hospital, Baylor University Medical Center (Dallas, Texas). Major inclusion criteria were age <75 years, having type A or B lesions, and use of a closure device. Patients with evidence of a recent acute coronary syndrome or who received ≥3 stents were not enrolled. Overall 298 patients were enrolled and completed baseline and follow-up ABCD-PCI study visits. Patients who did not complete the medication adherence screening tool (n = 14), described later, at the 2 administrations were excluded. This study was approved by the institutional review boards of Mount Sinai School of Medicine and Baylor University Medical Center. Patient consent for was obtained before enrollment.
Of relevance to the present analysis, data were collected after PCI but before hospital discharge using a self-administered questionnaire and at 30 days after PCI using an interview administered questionnaire. The prehospital discharge survey instrument included domains assessing sociodemographics, cigarette smoking, health insurance status, barriers to filling medications, patient–physician communication, beliefs about medication, and adherence to daily medications. Potential barriers to filling medications included skipping or taking smaller medication doses because of cost and lack of health insurance coverage for prescription medications. Medication beliefs were assessed using the 16-item Beliefs about Medicines Questionnaire. Adherence to daily medications before PCI was assessed using the 8-item Morisky Medication Adherence Scale (MMAS-8). Items on this scale reflect reasons for nonadherent behavior (e.g., forgetfulness, health beliefs, and side effects) and thus may be useful in identifying underlying causes of nonadherence. The MMAS-8 contains 7 “yes” or “no” responses and 1 item scored on a 5-point Likert-type scale. Scores on the MMAS-8 can range from 0 to 8, with scores <6, 6 to <8, and 8 reflecting low, medium, and high adherence, respectively. The MMAS-8 has been determined to be reliable and associated with blood pressure control and pharmacy fill rates in subjects with hypertension. For administration before hospital discharge, the MMAS-8 was tailored to assess adherence to all medications taken daily.
At 30 days after PCI, a separate questionnaire was administered by telephone by a trained research staff member. The 30-day follow-up questionnaire included an item about discontinuing clopidogrel. In patients who reported they did not discontinue clopidogrel, the MMAS-8 was administered. For administration during the 30-day follow-up interview, the MMAS-8 was tailored to apply to clopidogrel adherence. For example, the question “Do you sometimes forget to take your medications” was changed to “Do you sometimes forget to take your Plavix?” The outcome for the present analysis was discontinuation of clopidogrel and low adherence to clopidogrel 30 days after PCI. Because of the moderate sample of the present study, discontinuation of clopidogrel and low adherence to clopidogrel at 30 days after PCI were used as a pooled outcome, hereafter referred to as “low adherence.” Discontinuation at 30 days after PCI was assessed by self-report and low adherence was defined as scores <6 on the MMAS-8.
Characteristics of patients were calculated overall and by level of medication adherence (low, medium, and high) before PCI. Prevalence and odds ratios of low adherence to clopidogrel at 30 days after PCI were calculated for each item on prehospital discharge MMAS-8 administration. Distribution of adherence to clopidogrel (low, medium, and high) at 30 days after PCI was calculated by level of adherence to daily medications before PCI. Odds ratios for low adherence at 30 days after PCI were calculated for patient sociodemographics, medication-taking behaviors, beliefs about medications, and overall MMAS-8 scores assessed before hospital discharge after PCI. To assess how well factors assessed before hospital discharge after PCI discriminate between those who subsequently had versus did not have low clopidogrel adherence, c-statistics were calculated for variables associated (p <0.10) with low clopidogrel adherence in univariable analysis. In addition, c-statistics were calculated for each item and for overall scores on prehospital discharge administration of the MMAS-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 low adherence to clopidogrel at 30 days after PCI were calculated and restricted to patients who received a DES. All analyses were conducted using SAS 9.2 (SAS Institute, Cary, North Carolina).
Results
Mean age of patients included in this analysis was 55.8 years; 26% were women; and 33%, 15%, 26%, and 21% were non-Hispanic white, non-Hispanic black, Hispanic, and Asian, respectively ( Table 1 ). Overall, before hospital discharge after PCI, 32%, 35%, and 32% of patients reported low, medium, and high adherence to daily medications, respectively. Also, 73.9%, 81.0%, and 84.6% of participants with low, medium, and high adherence to daily medications before PCI received DESs (p = 0.102).
| Variable | Overall (n = 284) | Adherence Before PCI ⁎ | P Value for Trend | ||
|---|---|---|---|---|---|
| Low | Medium | High | |||
| (n = 92) | (n = 100) | (n = 92) | |||
| Age (years), mean ± SD | 55.8 ± 7.9 | 54.9 ± 7.8 | 56.2 ± 8.1 | 56.5 ± 7.6 | 0.34 |
| Women | 26.2% | 28.3% | 26.0% | 24.2% | 0.53 |
| Ethnicity | 0.15 | ||||
| Non-Hispanic white | 33.0% | 30.4% | 29.6% | 39.1% | |
| Non-Hispanic black | 14.9% | 15.2% | 16.3% | 13.0% | |
| Hispanic | 25.5% | 22.8% | 28.6% | 25.0% | |
| Asian | 21.3% | 23.9% | 21.4% | 18.5% | |
| Other | 5.3% | 7.6% | 4.1% | 4.4% | |
| Did not graduate from high school | 26.9% | 30.3% | 28.6% | 21.7% | 0.19 |
| Married | 68.7% | 65.2% | 69.0% | 71.7% | 0.34 |
| Income <$20,000 | 34.8% | 37.2% | 37.4% | 29.6% | 0.31 |
| Self-rated health, fair to poor | 37.1% | 44.6% | 40.4% | 26.1% | 0.01 |
| Current smoker | 15.0% | 18.7% | 15.3% | 11.0% | 0.15 |
| Skipped doses because of cost, sometimes or often | 7.9% | 14.6% | 8.1% | 1.1% | <0.001 |
| Smaller doses because of cost, sometimes or often | 4.7% | 11.2% | 3.0% | 0.0% | <0.001 |
| Prescriptions covered by any health insurance | 97.8% | 97.8% | 96.9% | 98.9% | 0.60 |
| Difficulty filling prescriptions, sometimes or often | 16.9% | 28.1% | 17.2% | 5.6% | <0.001 |
| Difficult reaching primary doctor | 11.6% | 15.7% | 12.2% | 6.7% | 0.06 |
| Comfortable asking doctor for instructions | 95.0% | 92.1% | 96.0% | 96.6% | 0.17 |
| Feeling that medicine is a necessity † | 47.2% | 53.3% | 47.0% | 41.3% | 0.10 |
| Feeling that medicine is a concern † | 48.9% | 59.8% | 55.0% | 31.5% | 0.001 |
| Received drug-eluting stent | 79.9% | 73.9% | 81.0% | 84.6% | 0.102 |
⁎ Determined before hospital discharge after percutaneous coronary intervention using the 8-item Morisky Medication Adherence Scale.
† Feelings of necessity and concern were determined using the Beliefs about Medication Questionnaire.
Overall 32 patients (11%), 68 patients (24%), and 184 patients (65%) had low, medium, and high adherence to clopidogrel at 30 days after PCI. Of those with low adherence, 11 (34%) had discontinued clopidogrel and 21 (66%) had a low MMAS-8 score. Of those with low adherence to daily medications before PCI, 20% had low adherence to clopidogrel in the month after PCI ( Figure 1 ). In contrast, 12% and 2% of those with medium and high adherence to daily medications before PCI had low adherence to clopidogrel at 30 days after PCI (p <0.001). Also, 49%, 65%, and 80% of patients with low, medium, and high adherence to daily medications before PCI had high adherence to clopidogrel after PCI (p <0.001).
Four of the 8 items that comprise the MMAS-8 (sometimes forgetting to take medications, missed taking medication in previous 2 weeks, sometimes forgetting to bring medications when leaving home, and having difficulty remembering to take all medications), assessed for daily medication use before PCI, were associated with higher odds ratios for low adherence to clopidogrel at 30 days after PCI ( Table 2 ). Odds ratios for low adherence to clopidogrel at 30 days after PCI were 6.13 (95% confidence interval [CI] 1.34 to 28.2) and 10.9 (95% CI 2.46 to 48.7) for patients with medium and low adherence to daily medications before PCI, respectively.
| Baseline Medication Adherence Scale Item | Low Adherence at 30 Days After PCI ⁎ (n = 32) | Odds Ratio (95% CI) for Low Adherence at 30 Days After PCI | P Value |
|---|---|---|---|
| Sometimes forget to take medicine | |||
| No | 7.1% | 1 (reference) | 0.004 |
| Yes | 18.8% | 3.03 (1.43–6.43) | |
| Missed taking medicine in previous 2 weeks † | |||
| No | 7.7% | 1 (reference) | <0.001 |
| Yes | 28.0% | 4.67 (2.13–10.2) | |
| Cut back or stopped taking medication because felt worse ‡ | |||
| No | 10.4% | 1 (reference) | 0.239 |
| Yes | 15.9% | 1.63 (0.66–4.03) | |
| Sometimes forget to bring medication when leaving home | |||
| No | 9.4% | 1 (reference) | 0.036 |
| Yes | 20.0% | 2.41 (1.06–5.47) | |
| Took all medicines on previous day † | |||
| No | 13.0% | 1 (reference) | 0.662 |
| Yes | 10.9% | 0.82 (0.33–2.01) | |
| Sometimes stop taking medication because feel problems are under control | |||
| No | 10.0% | 1 (reference) | 0.088 |
| Yes | 20.0% | 2.24 (0.89–5.65) | |
| Ever feel hassled about sticking to treatment plan | |||
| No | 9.0% | 1 (reference) | 0.066 |
| Yes | 16.7% | 2.02 (0.95–4.29) | |
| Have difficulty remembering to take all medications | |||
| Rarely/never | 6.1% | 1 (reference) | |
| Once in a while | 18.6% | 3.59 (1.49–8.63) | 0.004 |
| Sometimes | 36.0% | 8.81 (3.23–24.0) | <0.001 |
| Usually | 0.0% | N/A | N/A |
| Always | 0.0% | N/A | N/A |
| Baseline medication adherence scale category § | |||
| High | 2.2% | 1 (reference) | |
| Medium | 12.0% | 6.13 (1.34–28.20) | 0.002 |
| Low | 19.6% | 10.9 (2.46–48.7) | 0.02 |
⁎ Low adherence was defined as scores <6 on the 8-item Morisky Medication Adherence Scale or having discontinued clopidogrel.
† With the exception of medicines not taken as instructed by a physician because of percutaneous coronary intervention.
‡ Without telling their doctor.
§ Determined before hospital discharge after percutaneous coronary intervention using the 8-item Morisky Medication Adherence Scale.
Odds ratios for low adherence to clopidogrel after PCI associated with patient characteristics and behaviors are presented in Table 3 . Of note, odds ratios for low adherence to clopidogrel were 3.78 (95% CI 1.09 to 13.1) for patients who before PCI reported sometimes or often taking smaller doses because of cost, 3.06 (95% CI 1.36 to 6.87) for patients who reported sometimes or often having difficulty filling prescriptions, 2.46 (95% CI 0.97 to 6.27) for patients who had difficulty reaching their doctor, and 3.36 (95% CI 0.99 to 11.4) for patients who were not comfortable asking their doctor for instructions.
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