July 21, 2011

The Problem

A 67-year-old male with a history of hypertension, hyperlipidemia, atrial fibrillation, and knee degenerative joint disease presents to you for increasing left knee pain. He is currently on atenolol, pravastatin, and warfarin. His CHADS2 score is 1. Prior knee x-rays have shown bilateral tricompartmental narrowing with subchondral sclerosis, in the left knee, more so than in the right. You diagnose him with degenerative joint disease and recommend conservative therapy with another steroid injection. He informs you that the last time you set him up for a joint injection he was turned down because his international normalized ratio (INR) was supertherapeutic. He is also annoyed by having to come in to have his fingerstick INRs. He is an avid investor and read about a Food and Drug Administration approval of a new blood thinner that does not require monitoring. He asks you if this medication would be right for him. You talk to him briefly about dabigatran and report that patients in the higher-dose group (150 mg, b.i.d.) had lower rates of stroke, blood clots, and intracranial hemorrhage (ICH), compared with those who took warfarin but had similar rates of major hemorrhage. You wonder about the costs to the patient and the overall cost-effectiveness of the medication, compared with warfarin.

The Question

Is dabigatran more cost-effective than warfarin for preventing TIA-related stroke?

The Search

You log on to PubMed, enter "dabigatran" and "cost-effectiveness."

Dr. Ebbert and Dr. Tangalos are with the Mayo Clinic in Rochester, Minn. They reported having no conflicts of interest. To respond to this column or suggest topics for consideration, write to Dr. Ebbert and Dr. Tangalos at imnews@elsevier.com.

The Evidence

"Cost-effectiveness of dabigatran compared with warfarin for stroke prevention in atrial fibrillation, (Ann. Intern. Med. 2011;154:1-11).

• Study Design and Data Sources: A decision model analysis of data from the Randomized Evaluation of Long-Term Anticoagulation Therapy (RE-LY) trial and other published anticoagulation studies.

• Base Case: Cohort of patients at least age 65 years with a CHADS2 score of at least 1 and no contraindication to anticoagulation.

• Intervention: Anticoagulation with warfarin to an INR 2-3, low-dose dabigatran (110 mg, twice daily), and high dose (150 mg twice daily). We are currently interested in the high dose (150 mg, twice daily) presently because the low dose is not approved in the U.S. presently.

• Outcomes and Assumptions: Event rates were based primarily on the RE-LY study. Quality-adjusted life-years (QALYs), costs (in 2008 U.S. dollars), and incremental cost-effectiveness ratios over a lifetime time horizon were calculated. Costs reflected an ideal insurer covering inpatient and outpatient medical care and prescription costs. For warfarin, the annual medication expenses with the cost for 14 INR tests, the Center for Medicare and Medicaid Services reimbursement for 90-day anticoagulation management CPT code 99363 was used. In the sensitivity analysis, patients initiating warfarin anticoagulation were allowed to have up to 8 additional INR tests and CMS reimbursement at the higher rate allowed for anticoagulation initiation for 90 days (CPT code 99364).

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