Specialty Pharmacy Improves Adherence to Imatinib | Page 2
Published Online: December 05, 2013
Jay Visaria, PhD, MPH; Rochelle Henderson, PhD, MPA; and Sharon Glave Frazee, PhD, MPH
Patient records selected for the study showed at least 1 prescription claim for imatinib (Medi-Span Generic Product Identifier code 21-53-40-35-10) during the index period between January 1, 2011, and August 31, 2011. Analysis was limited to patients new to therapy, defined as patients with no imatinib claims in the 6 months prior to the index imatinib claim. To accurately assess newto-therapy status and postinitiation adherence, study patients were required to be continuously eligible for pharmacy benefits 6 months prior to and 12 months following the index imatinib claim. Medicare and Medicaid beneficiaries were excluded from the analysis since these patients’ pharmacy benefit design is different from that of commercial patients. Patients who paid 100% of the out-of-pocket cost for imatinib were also excluded from the analysis because it was likely that imatinib was not covered by the pharmacy benefi t for these patients. We may not have captured all transactions for patients who paid 100% of their medication cost. These patients may not have used the pharmacy benefit and hence generated no claims. Each study patient was followed for 365 days after the index imatinib claim.
The outcome of interest was optimum imatinib adherence, a dichotomous variable defi ned as a proportion of days covered (PDC) of 90% or higher during follow-up. The PDC was calculated as the number of days the patient had medication on hand during the 365-day followup period divided by 365.18,19 When the days of supply from a new fill overlapped the last 7 days of supply of imatinib from a previous fill, the fill date for the new fill was adjusted forward to the depletion date of the earlier fill. The patients were thus credited for finishing the supply of imatinib from the previous fill before using the supply of imatinib from the subsequent fill. In situations where multiple claims for imatinib representing different drug strengths (100 mg and 400 mg) occurred concurrently on the same fill date, it was assumed that medication from both claims would be used concurrently and no adjustment was made. The PDC was also evaluated as a continuous variable.
A literature review identifi ed adherence channel confounders, which were included in multivariate analysis. Demographic confounders included patient sex and age at the time of the index imatinib claim.8,9,20,21 Because urbanicity may impact access to pharmacies and therefore adherence,21 we created a dichotomous indicator for whether the 5-digit zip code of the patient’s residence was inside the urban center of a US Census–defined Core Based Statistical Area.22 Patient out-of-pocket cost burden was determined by averaging the amounts paid by the patient (copayment, coinsurance, and deductible) per 30-day supply of imatinib during the follow-up period.20,21 A proxy for patient medication burden9 was the number of therapy classes (as established by the number of unique 2-digit Medi-Span Generic Product Identifi er codes) used by the patient during the follow-up period.21 Because the use of more days of supply per prescription may also improve adherence,23 the average number of days of supply per unadjusted imatinib prescription was included as a covariate. Finally, an indicator was created to identify patients who had at least 1 imatinib claim paid by a plan sponsor whose pharmacy benefit design included a days-of-supply optimization program for specialty medications including imatinib.
As part of this program, patients starting a new course of imatinib therapy were provided medication in 30-day increments for the initial 90 days of therapy, after which patients transitioned from 30-day prescriptions to 90-day prescriptions of imatinib for the remainder of follow-up. Although the program was intended to maximize appropriate use, it may have affected the imatinib PDC in 2 ways. First, patients who completed the first 90 days of therapy would have a higher PDC based on having more days of supply per prescription. Second, those patients who discontinued therapy before completing the first 90 days of therapy would have a lower PDC based on having fewer days of supply per prescription.
Differences in age and imatinib PDC between the specialty pharmacy group and other pharmacy group were evaluated using t tests. Differences in out-of-pocket pharmacy spending per 30-day adjusted imatinib claim, medication burden, and days of supply per unadjusted imatinib prescription were evaluated using nonparametric Wilcoxon rank sum tests because the distributions of these variables were highly skewed. Differences in categorical variables were evaluated with χ2 tests. Logistic regression models were created with dichotomous imatinib adherence as the primary dependent variable, dispensing channel as the primary independent variable, and other covariates. Multivariate adjustment for continuous imatinib PDC was performed using ordinary least squares regression with PDC as the dependent variable, dispensing channel as the primary independent variable, and other known confounders as covariates.
The Figure outlines the patient selection procedure. A total 6121 patients had at least 1 prescription claim for imatinib between January 1, 2011, and August 31, 2011. Excluded were 1550 patients who were not continuously eligible for pharmacy benefi ts 6 months before and 12 months after the index imatinib claim, 3556 patients who had a claim for imatinib in the 6 months prior to the index claim, 2 patients with inconsistencies in their eligibility information, 292 whose pharmacy costs were paid by Medicare Part D, 3 who were Medicaid beneficiaries, and 14 who paid the entire cost of imatinib out of pocket. The fi nal study sample consisted of 704 patients, of which 433 were in the specialty pharmacy group and 271 in the other pharmacy group.
Selected characteristics of the study patients are presented in Table 1. Patients in the 2 study groups had similar distributions of age, sex, and urbanicity. Compared with the other pharmacy group patients, patients in the specialty pharmacy group had lower out-of-pocket imatinib costs and a lower medication burden. Patients in the specialty pharmacy group had on average about 15 additional days of imatinib per prescription. More patients in the specialty pharmacy group had at least 1 fill of imatinib through a benefit that encouraged 90-day fills only for patients stabilized on imatinib therapy.
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