Managed Care - October 2008 - (Page OA2) Introduction INR device in addition to regular office visits with the health care practitioner. Each week, the patient commuChallenges of managing patients nicates the INR to the practitioner, who then instructs the on warfarin therapy patient about any dose adjustments that may be needed. Oral anticoagulation therapy with warfarin is effective PST is not a stand-alone management method; ideally, in reducing the risk of thromboembolism in patients it should be combined with periodic visits to an anticowith hereditary or acquired thrombophilia, heart valve agulation clinic or a health care practitioner’s office on replacement, atrial fibrillation (AF), and other conditions a predetermined schedule for clinical assessment, pa(Heneghan 2006) (P=.001). The goals of oral anticoagtient education, and periodic parallel testing of the paulant therapy are to prevent thromboembolism and to tient’s INR device. Patient self-management (PSM) ocminimize the risk of bleeding complications by achievcurs in addition to all the components of a weekly ing and maintaining the international normalized ratio self-testing program, and includes teaching the patient (INR) within an appropriate target range. However, warto follow a practitioner-prescribed, dose-adjustment alfarin’s narrow therapeutic range, variable biological efgorithm based on weekly INR values. fects, and potential for drug and food interactions, inIn addition to the extensive body of evidence supcluding fluctuations in patient dietary intake of vitamin porting the efficacy, safety, and improved quality of life K-containing foods, present challenges to reaching these associated with PST (Ansell 2005, Sawicki 1989, Henegoals (Ansell 2004). Because of these factors, regular INR ghan 2006), additional factors (discussed later in this monitoring is required to determine dose adjustments monograph) support its incorporation into the U.S. care that may be necessary to maintain the INR in the target model for patients who require oral anticoagulation. As range. The mean plasma half-life of warfarin is approxthe general patient population has become better inimately 40 hours, and the mean terminal half-life of a sinformed about health care, patients desire a more active gle dose is approximately 1 week (warfarin PI 2007). role in the management of their health. PST, like home U.S. Food and Drug Administration-approved labeling blood-glucose monitoring by patients with diabetes, is a of warfarin now includes a black box warning regarding simple and practical method that enables more frequent the risks of major or fatal bleeding. Risk factors for bleedtesting, and has been demonstrated to improve INR coning include high intensity of anticoagulation (INR>4.0), trol and significantly reduce the risk of bleeding and age 65 or older, highly variable INRs, history of gastrointhrombotic complications. testinal (GI) bleeding, hypertension, cerebrovascular disease, serious heart disease, anemia, malignancy, trauma, Need for oral anticoagulation therapy renal insufficiency, concomitant drugs, and a prolonged expected to increase duration of warfarin therapy. Those at high risk of bleedThe incidence of venous thromboembolism (VTE) ing may benefit from more frequent INR monitoring, rises exponentially with age and increases sharply in pacareful dose adjustment to the desired INR, and a shorter duration of therapy (warfarin PI 2007). In the United States, approximately 75 perTABLE 1 cent of patients taking warfarin are managed Selected studies of patient self-testing (PST) individually by a physician or other practiand patient self-management (PSM) tioner (CMS 2008), with periodic office visits that include INR testing performed either by % patients within centralized laboratory methods or with pointINR target rangea Patient of-care (POC) INR devices in the office. In this Study N population Usual care PST/PSM setting, referred to as usual care, patients are typically evaluated by the practitioner once White 1989 46 Mixed 75 93 every 4–6 weeks, any INR-based dose adjustAnsell 1995 40 Mixed 68 89 ments are then prescribed, and patients reBeyth 2000 325 Mixed 33 56 Sawicki 1989b 179 Mixed 43 53 main on that dose until the next office visit. AlHorstkotte 1998 150 MHV 59 92 ternatively, monitoring by anticoagulation Körtke 2001 1200 MHV 62 80 clinics provides a standardized system of paVoller 2005 202 AF 59 68 tient management, and this type of care has been associated with improved outcomes relAF=atrial fibrillation, MHV=mechanical heart valve, mixed=patient ative to the usual care model (Ansell 2005). population with regard to indication for therapy. a Patient self-testing Patient self-testing (PST) may consist of weekly, as indicated, INR testing with a home b Rounded to nearest whole digit. Results indicate percentage of patients in the therapeutic range at 6 months. 2 MANAGED CARE / SUPPLEMENT
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