Aggregated Odds Ratio Research Articles

Anticoagulants or antiplatelet therapy for non-rheumatic atrial fibrillation and flutter.

Atrial fibrillation (AF) carries a high risk of stroke and other thromboembolic events. Appropriate use of drugs to prevent thromboembolism in patients with AF involves comparing the patient's risk of stroke to the risk of hemorrhage from medication use. To quantify risk of stroke, major hemorrhage and death from using medications that have been rigorously evaluated for prevention of thromboembolism in AF. Articles were identified through the Cochrane Collaboration's CENTRAL database and MEDLINE until December 1999. Included Randomized controlled trials of drugs to prevent thromboembolism in adults with non-postoperative AF. Excluded RCTS of patients with rheumatic valvular disease. Data were abstracted by two reviewers. Odds ratios from all qualitatively similar studies were combined, with weighting by study size, to yield aggregate odds ratios for stroke, major hemorrhage, and death for each drug. Fourteen articles were included in this review. Warfarin was more efficacious than placebo for primary stroke prevention [aggregate odds ratio (OR) of stroke=0.30 [95% Confidence Interval (C.I.) 0.19,0.48]], with moderate evidence of more major bleeding [ OR= 1.90 [95% C.I. 0.89,4.04].]. Aspirin was inconclusively more efficacious than placebo for stroke prevention [OR=0.68 [95% C.I. 0.29,1.57]], with inconclusive evidence regarding more major bleeds [OR=0.81[95% C.I. 0.37,1.78]]. For primary prevention, assuming a baseline risk of 45 strokes per 1000 patient-years, warfarin could prevent 30 strokes at the expense of only 6 additional major bleeds. Aspirin could prevent 17 strokes, without increasing major hemorrhage. In direct comparison, there was moderate evidence for fewer strokes among patients on warfarin than on aspirin [aggregate OR=0.64[95% C.I. 0.43,0.96]], with only suggestive evidence for more major hemorrhage [OR =1.58 [95% C.I. 0.76,3.27]]. However, in younger patients, with a mean age of 65 years, the absolute reduction in stroke rate with warfarin compared to aspirin was low (5.5 per 1000 person-years) compared to an older group (15 per 1000 person-years). Low-dose warfarin or low-dose warfarin with aspirin was less efficacious for stroke prevention than adjusted-dose warfarin. The evidence strongly supports warfarin in AF for patients at average or greater risk of stroke, although clearly there is a risk of hemorrhage. Although not definitively supported by the evidence, aspirin may prove to be useful for stroke prevention in sub-groups with a low risk of stroke, with less risk of hemorrhage than with warfarin. Further studies are needed of low- molecular weight heparin and aspirin in lower risk patients.

Prevention of thromboembolism in atrial fibrillation. A meta-analysis of trials of anticoagulants and antiplatelet drugs.

Appropriate use of drugs to prevent thromboembolism in patients with atrial fibrillation (AF) involves comparing the patient's risk of stroke and risk of hemorrhage. This review summarizes the evidence regarding the efficacy of these medications. We conducted a meta-analysis of randomized controlled trials of drugs used to prevent thromboembolism in adults with nonpostoperative AF. Articles were identified through the Cochrane Collaboration's CENTRAL database and MEDLINE until May 1998. Eleven articles met criteria for inclusion in this review. Warfarin was more efficacious than placebo for primary stroke prevention (aggregate odds ratio [OR] of stroke = 0.30, 95% confidence interval [CI] 0.19, 0.48), with moderate evidence of more major bleeding (OR 1.90; 95% CI 0.89, 4.04). Aspirin was inconclusively more efficacious than placebo for stroke prevention (OR 0.56, 95% CI 0.19, 1.65), with inconclusive evidence regarding more major bleeds (OR 0.81, 95% CI 0.37, 1.77). For primary prevention, assuming a baseline risk of 45 strokes per 1,000 patient-years, warfarin could prevent 30 strokes at the expense of only 6 additional major bleeds. Aspirin could prevent 17 strokes, without increasing major hemorrhage. In direct comparison, there was evidence suggesting fewer strokes among patients on warfarin than among patients on aspirin (aggregate OR 0.64, 95% CI 0.43, 0.96), with only suggestive evidence for more major hemorrhage (OR 1.60, 95% CI 0.77,3.35). However, in younger patients, with a mean age of 65 years, the absolute reduction in stroke rate with warfarin compared with aspirin was low (5.5 per 1,000 person-years) compared with an older group (15 per 1,000 person-years). In general, the evidence strongly supports warfarin for patients with AF at average or greater risk of stroke. Aspirin may prove to be useful in subgroups with a low risk of stroke, although this is not definitively supported by the evidence.

Variation in proficiency testing performance by testing site.

Congress enacted the Clinical Laboratory Improvement Amendments of 1988 (CLIA) to promote uniform quality and standards among all testing sites in the United States. The performance indicators specified in the legislation are proficiency testing (PT) performance and periodic inspections. To evaluate variation in PT performance by type of testing facility during the first year of compulsory participation under CLIA. All 1994 PT score data electronically reported to the Health Care Financing Administration as a component of compliance with the CLIA regulations were obtained. Over 1.2 million PT event scores from 17058 unique testing sites were sorted into 2 groups based on the type of testing facility: hospitals and independent laboratories (HI) and all other testing sites (AOT). Satisfactory and unsatisfactory performance rates for HI and AOT for each analyte and/or test, according to the criteria specified by the CLIA regulations. The aggregate rates of satisfactory event performance for all regulated analytes, tests, and specialties were 97% and 91% for the HI and AOTgroups, respectively. The aggregate odds ratio for unsatisfactory PT event performance for the AOT group compared with the HI group was 2.89, with a range of 2.19 to 7.51 for the individual analytes. There was a consistent difference in PT performance during the first full year of compulsory PT under the CLIA regulations based on the type of testing facility performing the analysis. Traditional testing sites achieved higher rates of satisfactory performance than newly regulated, alternative testing sites.