Do open label blinded outcome studies of novel anticoagulants versus warfarin have equivalent validity to those carried out under double-blind conditions?

Recent anticoagulants for stroke prevention in AF have been tested in active comparator controlled studies versus warfarin using two designs: double-blind, double-dummy and prospective randomised, open blinded endpoint (PROBE). The former requires elaborate procedures to maintain blinding, while PROBE does not. Outcomes of double-blind and PROBE designed studies of novel anticoagulants for AF, focusing on warfarin controls, were explored. Major, Phase III warfarin-controlled trials for stroke prevention in AF were identified. Odds ratios (ORs) of key outcomes for active comparators versus VKA and event rates for VKA arms were compared between designs, in context of baseline demographics and inclusion criteria. Identified trials studied five novel anticoagulants in three each of PROBE and double-blind design. For ORs of results across studies and outcomes, there was little pattern differentiating the two designs. Among VKA-control subjects, event rates for the primary outcome (stroke or systemic embolism) in PROBE trials at 1.74 %/year (95% confidence interval: 1.54-1.95) was not significantly different from that in double-blind trials, at 1.88 (1.73-2.03). Among other outcomes, VKA-treated subjects in both trial designs had similar event rates, apart from higher all-cause mortality in ROCKET AF, and lower myocardial infarction rates among the PROBE study patients. Although there are differences in outcome between PROBE and double blind trials, they do not appear to be design-related. The exacting requirements of double-blinding in AF trials may not be necessary.

Ischaemic stroke and bleeding rates in 'real-world' atrial fibrillation patients.

Stroke prevention guidelines recommend oral anticoagulants (OAC) for atrial fibrillation (AF) patients at moderate/high risk of stroke, and antiplatelet or no therapy for those at low/moderate risk. Outcomes for AF patients receiving antiplatelet/no therapy in 'real-life' clinical practice were explored. This study compared clinical event rates (stroke/bleeding) for AF patients treated with OAC therapy, antiplatelets or no therapy in usual clinical practice to event rates in OAC-treated AF patients from optimally-monitored 'real-life' settings (anticoagulation clinics). We searched biomedical literature (1994-2010) using PubMed to identify 'real-world' studies of clinical event rates for AF patients receiving OAC therapy, antiplatelets, or no therapy; event rates were extracted for each treatment and setting. We identified 136 studies of thromboembolic events and 86 of bleeding events. Ischaemic stroke rates (30 studies) were higher for AF patients receiving no therapy (median: 4.45/100 person-years; range: 0.25-5.9) or antiplatelet-therapy (median: 4.45/100 person-years; range: 2.0-10) compared to OAC-treated patients monitored in anticoagulation clinics (median: 1.72/100 person-years; range: 0.97-2.00), or from a non-specialized setting (median 1.66/100 person-years; range: 0-4.9). Major bleeding rates (32 studies) for patients receiving antiplatelet/no therapy were similar to OAC-treated patients from both clinical settings. As in randomised clinical trials, AF patients in 'real-world' clinical practice receiving antiplatelet/no therapy have higher rates of ischaemic stroke than OAC-treated patients. Antiplatelet/no therapy was associated with similar bleeding rates to OAC therapy. Increasing utilisation of anticoagulants in clinical practice could improve patient outcomes.

Characterization of the proportion of untreated and antiplatelet therapy treated patients with atrial fibrillation.

Despite the efficacy of oral anticoagulants for stroke prevention in atrial fibrillation (AF), evidence suggests that many patients with AF who should be treated with vitamin K antagonists (VKAs) are treated with antiplatelet therapy or remain untreated. The aims of this study were to determine the proportion of patients with AF in each treatment category in clinical practice and to ascertain whether treatment is appropriate for stroke risk. An extensive search of the biomedical research published since 1994 was performed. Studies delineating the treatment of patients with AF were captured. Seventy-eight studies pertaining to the treatment of patients with AF were identified; 56 studies, containing data from 1980 to 2007, met the inclusion criteria. Over time, the use of VKA therapy for stroke prevention increased, while the proportion of untreated patients decreased; antiplatelet use remained static. Looking at the more recent data, (collected from 2000 onward), the proportion of patients receiving no therapy ranged from 4% to 48% (median 18%), antiplatelet therapy from 10% to 56% (median 30%), and VKA therapy from 9% to 86% (median 52%). Although most studies showed a decrease in the proportion of antiplatelet-treated and untreated patients with increasing stroke risk (12 of 14 studies), many patients at moderate or high risk for stroke were not treated according to guidelines. In conclusion, this review shows that up to 56% of patients with AF are treated with antiplatelet therapy, and up to 48% receive no therapy regardless of stroke risk level. This may reflect the inconvenience associated with VKA use, inadequate assessment of stroke risk, or poor adherence to treatment guidelines.

Underuse of oral anticoagulants in atrial fibrillation: a systematic review.

BACKGROUND: Atrial fibrillation is associated with substantial mortality and morbidity from stroke and thromboembolism. Despite an efficacious oral anticoagulation therapy (warfarin), atrial fibrillation patients at high risk for stroke are often under-treated. This systematic review compares current treatment practices for stroke prevention in atrial fibrillation with published guidelines. METHODS: Literature searches (1997-2008) identified 98 studies concerning current treatment practices for stroke prevention in atrial fibrillation. The percentage of patients eligible for oral anticoagulation due to elevated stroke risk was compared with the percentage treated. Under-treatment was defined as treatment of <70% of high-risk patients. RESULTS: Of 54 studies that reported stroke risk levels and the percentage of patients treated, most showed underuse of oral anticoagulants for high-risk patients. From 29 studies of patients with prior stroke/transient ischemic attack who should all receive oral anticoagulation according to published guidelines, 25 studies reported under-treatment, with 21 of 29 studies reporting oral anticoagulation treatment levels below 60% (range 19%-81.3%). Subjects with a CHADS(2) (congestive heart failure, hypertension, age >75 years, diabetes mellitus, and prior stroke or transient ischemic attack) score >or=2 also were suboptimally treated, with 7 of 9 studies reporting treatment levels below 70% (range 39%-92.3%). Studies (21 of 54) using other stroke risk stratification schemes differ in the criteria they use to designate patients as "high risk," such that direct comparison is not possible. CONCLUSIONS: This systematic review demonstrates the underuse of oral anticoagulation therapy for real-world atrial fibrillation patients with an elevated risk of stroke, highlighting the need for improved therapies for stroke prevention in atrial fibrillation.