Published Online: December 21, 2011
Nathan W. Carroll, MHA; and Michael P. Dorsch, PharmD, MS
Objectives: To propose a model in which insurers work with hospitals to provide a discharge supply of antiplatelet medication to patients receiving stents and to examine the cost implications of this strategy.
Study Design: A decision tree was modeled using data from previously published research. The study adopts an insurer’s perspective.
Methods: Data on patient delays in filling antiplatelet prescriptions and rates of associated adverse events were taken from published research. The costs of adverse events (death or acute myocardial infarction [AMI]) are taken from Healthcare Cost and Utilization Project estimates of hospital costs for diagnosis-related groups associated with AMI.
Results: In the base case, expected costs totaled $1782 when stent implantation patients were provided with a discharge supply of medication and $1857 under the current standard of care, a difference of $75. Insurers can supply up to 60 days of medication without increasing total costs. The strategy of offering a discharge supply of medication is cost saving under a range of estimated rehospitalization costs and medication costs. However, this result is dependent on the ability of a discharge supply of medication to reduce rates of death or AMI.
Conclusions: Providing discharge supplies of antiplatelet medication resulted in lower overall costs for insurers in most of the cases modeled.
(Am J Manag Care. 2011;17(12):803-810)
Managed care plans should consider waiving copayments on antiplatelet medications for percutaneous coronary intervention (PCI) patients and collaborating with hospitals to ensure that patients receive a supply of these medications upon discharge.
Research has shown that failure to begin antiplatelet therapy promptly after PCI puts patients at increased risk for acute myocardial infarction or death, but many patients delay filling prescriptions for these medications.
In most of the scenarios modeled here, the expected costs of these complications to insurers exceed the cost of providing copay-free discharge supplies of medication to PCI patients.
Developments in antiplatelet therapy for patients undergoing cardiac stent implantation have reduced the incidence of thrombosis in patients receiving cardiac stents.1 However, thrombosis is still an all-too-common occurrence with grave consequences for patient health. Sixty-four percent of patients with stentrelated thrombosis experience either an acute myocardial infarction (AMI) or death.2 Revascularization is costly also. Patients requiring revascularization within a year of percutaneous coronary intervention (PCI) incur almost $25,000 more in medical expenses than those that do not.3 A great deal of research has been devoted to describing costs and outcomes associated with antiplatelet therapies for stent patients. However, much less information is available on the cost implications of adherence to these therapies.
Payers may have an opportunity to reduce their medical losses by designing benefits that encourage continuity of antiplatelet therapy during the period immediately following hospital discharge. One study of 3 large US managed care organizations found that 16.3% of patients undergoing stent implantation delayed filling their antiplatelet prescription. The median delay between a PCI patient’s discharge from the hospital and the time the patient first fills the antiplatelet prescription was 3 days.4 Past studies of unusually restrictive prior authorization programs in Canada have found median delays in filling antiplatelet prescriptions of 9 days.5 Given antiplatelet medications’ mechanisms of action, it is not surprising that a gap in therapy after hospital discharge is associated with an increased risk of poor outcomes. Even among a population of patients receiving drug-eluting stents, patients with a delay of 1 day or more in filling an antiplatelet prescription after discharge are significantly more likely to experience death or a myocardial infarction.4 Furthermore, higher copayments for medications are associated with an increased risk of rehospitalization in acute coronary syndrome patients receiving stents, as well as higher average follow-up costs of care.6
There is reason to believe that the way in which payers choose to administer benefits may impact beneficiaries’ health outcomes as well as the total costs of treatment. If this is the case, payers may have an opportunity to reduce medical losses and improve the quality of cardiac care through changes in benefit design. Insurers could develop partnerships with hospitals to fund hospitals’ provision of discharge supplies of medication to patients receiving cardiac stents. This study examines the cost implications of such a strategy.
A decision model, using a payer’s perspective, was developed to evaluate this strategy. The 2 alternatives are (1) the current state of care, in which patients are responsible for filling their prescriptions for antiplatelet medications and insurers charge a copayment for those medications; and (2) an alternative strategy in which an insurer waives the copayment for a small discharge supply of antiplatelet medication that is provided to a patient by the hospital. The decision tree was modeled using TreeAge Pro software (TreeAge Software Inc, Williamstown, Massachusetts) and is presented in Figure 1. Probabilities of patient adherence (defined here as a patient filling a prescription on the day of discharge) and adverse events (defined here as the occurrence of death or AMI) as well as the costs of adverse events were estimated based on published studies. Model parameters are provided in Table 1. Sensitivity analysis and Monte Carlo simulation were conducted to evaluate how robust conclusions were to changes in the model assumptions.
Outcome and Adherence Measures
In the base case, 7.9% of patients filling a prescription for an antiplatelet medication immediately following discharge were estimated to experience death or AMI compared with 14.2% of patients who had at least a 1-day delay.4 Similarly, the base case estimates that 83.65% of patients will fill a prescription without delay.4 This estimate may overstate the true percentage of patients who fill antiplatelet prescriptions upon discharge. Other studies have found results ranging from 64%5 to 54%.7 The 83.65% estimate for patient adherence is conservative. If the true rate of adherence is lower than 83.65%, the model’s estimates of the costs associated with standard treatment will underestimate the true cost of the standard treatment. In that case, the savings afforded by the alternative strategy (in which patients are provided discharge medication) will be higher than estimated here. The model assumed that rates of death or AMI under the alternative strategy would be equal to adverse event rates for the group of patients filling prescriptions upon discharge. The model also assumed that under the alternative strategy 7 days of medication is provided by the hospital patient is completely adherent to therapy throughout the rest of the year. This supply is enough to cover the 3- to 4-day average delay in filling reported by some studies. 4,7 Like other assumptions, this estimate was relaxed in sensitivity analysis.
The model compared the expected cost of rehospitalization for AMI with the higher medication costs insurers would face in supplying patients with discharge supplies of antiplatelet medication without charging copayments. Patients who did not experience death or AMI incurred medication costs for 12 months per accepted guidelines.8 Costs related to hospitalizations were estimated to average $8111 based on hospital costs reported by the Healthcare Cost and Utilization Project for diagnosis-related groups (DRGs) 280-285.9 These are actual hospital costs (as opposed to charges) estimated based on hospital- specific cost-to-charges ratios reported to the Centers for Medicare & Medicaid Services. These DRGs include services related to AMI for patients with and without complications and comorbidities. They include costs for services to patients who are discharged alive, as well as for patients who expire. These DRG codes, their descriptions, and the associated costs are listed in Table 2. These cost estimates only included hospitalization costs. Any additional costs related to an AMI but attributable to physician services or non-antiplatelet medication costs were not included in these estimates. In addition, any amount paid by insurers in excess of hospital costs was not included in these estimates. These are conservative estimates and if incorrect they would bias the cost minimization analysis in favor of the standard therapy.
In addition to differences in the costs and rates of death or AMI, cost differences between the standard and alternative treatments are driven by differences in medication costs, which were modeled on a cost-per-day basis. Under the standard treatment, insurers bear the cost of a year of treatment. However, it is possible that patient delays in filling prescriptions represent medication savings for an insurer. This would be the case if patients who delay filling prescriptions for antiplatelet medications do not extend the course of their therapy to make up for a delay in beginning therapy. As a result, the model calculated drug costs for a full 365 days of therapy for the alternative treatment but for 358 days (365 days less a 7-day delay) under the standard treatment. It is unlikely that a patient would actually reduce his course of therapy after an initial 7-day delay in filling a prescription. However, this is a conservative assumption and, if incorrect, would bias the results in favor of the standard treatment.
Medication costs under the alternatives also differ with respect to patient copayment. Under the standard treatment, patients are charged a copayment for all medication, which offsets the insurers’ expenses. The alternative treatment, however, provides a discharge supply of medication without a patient contribution. Copayments for a 30-day supply were estimated based on the $25.19 average 2009 retail copayment for preferred branded medications reported by the Pharmacy Benefit Management Institute.10 Copayment costs for both the standard and alternative treatments were considered on a per day basis. Consistent with published reports, the base case assumed that a 7-day supply of discharge medication would be provided. Medication cost was set at $3.95 per day, which represents average wholesale price less the average 16% discount offered to retail pharmacies for brand-name medications.10
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