ContextThe increasing use of Internet-based learning in health professions education may be informed by a timely, comprehensive synthesis of evidence of effectiveness.Objectives To summarize the effect of Internet-based instruction for health professions learners compared with no intervention and with non-Internet interventions.

Interactivity, practice exercises, repetition, and feedback seem to be associated with improved learning outcomes, although inconsistency across studies tempers conclusions. Evidence for other instructional variations remains inconclusive.

Teaching on the Web involves more than putting together a colorful webpage. By consistently employing principles of effective learning, educators will unlock the full potential of Web-based medical education.

OBJECTIVES Educators often speak of web-based learning (WBL) as a single entity or a cluster of similar activities with homogeneous effects. Yet a recent systematic review demonstrated large heterogeneity among results from individual studies. Our purpose is to describe the variation in configurations, instructional methods and presentation formats in WBL.METHODS We systematically searched MEDLINE, EMBASE, ERIC, CINAHL and other databases (last search November 2008) for studies comparing a WBL intervention with no intervention or another educational activity. From eligible studies we abstracted information on course participants, topic, configuration and instructional methods. We summarised this information and then purposively selected and described several WBL interventions that illustrate specific technologies and design features. RESULTSWe identified 266 eligible studies. Nearly all courses (89%) used written text and most (55%) used multimedia. A total of 32% used online communication via e-mail, threaded discussion, chat or videoconferencing, and 9% implemented synchronous components. Overall, 24% blended web-based and non-computerbased instruction. Most web-based courses (77%) employed specific instructional methods, other than text alone, to enhance the learning process. The most common instructional methods (each used in nearly 50% of courses) were patient cases, self-assessment questions and feedback. We describe several studies to illustrate the range of instructional designs. CONCLUSIONS

clinicaltrials.gov identifier NCT00667940

No difference was found between WB and paper-based formats in knowledge-test score change, but residents preferred learning with WB modules and spent less time doing so. Passwords appeared to impede use of WB modules. WB learning is effective, well accepted, and efficient. Research should focus on aspects of WB instruction that will enhance its power as a learning tool and better define its role in specific settings.

ADE = adverse drug event; AEI = American Enterprise Institute; ASPE = allele-specific primer extension; CYP2C9 = cytochrome P450 2C9; INR = international normalized ratio; PCR = polymerase chain reaction; SNP = single-nucleotide polymorphism; VitKH 2 = vitamin K hydroquinone; VKOR = vitamin K epoxide reductase; VKORC1 = VKOR complex, subunit 1 W arfarin is a well-accepted therapy used for the prevention of stroke in patients with atrial fibrillation, for prophylaxis of venous thromboembolism and pulmonary embolism in patients with prosthetic heart valves and myocardial infarction, and for prevention of pulmonary embolism or deep venous thrombosis in patients undergoing orthopedic surgery or with a history of venous or arterial thromboembolism. Many reviews and clinical practice guidelines (summarized by Ansell et al, 1 Baglin et al, 2 Flockhart et al, 3 Husted et al, 4 and Singer et al 5 ) outline the substantial benefits of warfarin therapy for the prevention of strokes in these patients. The American Enterprise Institute (AEI)-Brookings Joint Center for Regulatory Studies Report, which reviewed the use of warfarin in the United States, estimates that approximately 2 million US citizens are prescribed warfarin annually. 6 In 2003, a total of 21.2 million prescriptions were written for oral warfarin in the United States. 7 Warfarin interferes with coagulation by inhibiting regeneration of the reduced form of vitamin K, a cofactor in the γ-glutamyl-carboxylase -mediated activation of coagulation factors II, VII, IX, and X ( Figure 1). The oxidized, inactive form of vitamin K is converted to the reduced form of vitamin K by vitamin K epoxide reductase (VKOR); warfarin inhibits VKOR, resulting in less of the reduced form of vitamin K available to support the factor carboxylation required to sustain the coagulation cascade. 8 Warfarin has a narrow therapeutic index that contributes either to therapeutic failure (potentially leading to stroke or other complications) or therapeutic excess (potentially leading to bleeding and hemorrhage). Many surveys have described the incidence of warfarin-related adverse drugThe antithrombotic benefits of warfarin are countered by a narrow therapeutic index that contributes to excessive bleeding or cerebrovascular clotting and stroke in some patients. This article reviews the current literature describing warfarin sensitivity genotyping and compares the results of that review to the findings of our study in 189 patients at Mayo Clinic conducted between June 2001 and April 2003. For the review of the literature, we identified relevant peer-reviewed articles by searching the Web of Knowledge using key word warfarin-related adverse event. For the 189 Mayo Clinic patients initiating warfarin therapy to achieve a target international normalized ratio (INR) in the range of 2.0 to 3.5, we analyzed the CYP2C9 (cytochrome P450 2C9) and VKORC1 (vitamin K epoxide reductase complex, subunit 1) genetic loci to study the relationship among the initial warfarin dose, steady-state dose, time to ach...

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