Cochrane Reviews have recently started including the quantity I 2 to help readers assess the consistency of the results of studies in meta-analyses. What does this new quantity mean, and why is assessment of heterogeneity so important to clinical practice? 

Systematic reviews and meta-analyses can provide convincing and reliable evidence relevant to many aspects of medicine and health care.1 Their value is especially clear when the results of the studies they include show clinically important effects of similar magnitude. However, the conclusions are less clear when the included studies have differing results. In an attempt to establish whether studies are consistent, reports of meta-analyses commonly present a statistical test of heterogeneity. The test seeks to determine whether there are genuine differences underlying the results of the studies (heterogeneity), or whether the variation in findings is compatible with chance alone (homogeneity). However, the test is susceptible to the number of trials included in the meta-analysis. We have developed a new quantity, I 2, which we believe gives a better measure of the consistency between trials in a meta-analysis.

Assessment of the consistency of effects across studies is an essential part of meta-analysis. Unless we know how consistent the results of studies are, we cannot determine the generalisability of the findings of the meta-analysis. Indeed, several hierarchical systems for grading evidence state that the results of studies must be consistent or homogeneous to obtain the highest grading.2–4

Tests for heterogeneity are commonly used to decide on methods for combining studies and for concluding consistency or inconsistency of findings.5 6 But what does the test achieve in practice, and how should the resulting P values be interpreted?

A test for heterogeneity examines the null hypothesis that all studies are evaluating the same effect. The usual test statistic …

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Measuring inconsistency in meta-analyses

Systematic review and meta-analysis

Systematic reviews and meta-analyses are essential to summarize evidence relating to efficacy and safety of health care interventions accurately and reliably. The clarity and transparency of these reports, however, is not optimal. Poor reporting of systematic reviews diminishes their value to clinicians, policy makers, and other users.

Since the development of the QUOROM (QUality Of Reporting Of Meta-analysis) Statement—a reporting guideline published in 1999—there have been several conceptual, methodological, and practical advances regarding the conduct and reporting of systematic reviews and meta-analyses. Also, reviews of published systematic reviews have found that key information about these studies is often poorly reported. Realizing these issues, an international group that included experienced authors and methodologists developed PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses) as an evolution of the original QUOROM guideline for systematic reviews and meta-analyses of evaluations of health care interventions.

The PRISMA Statement consists of a 27-item checklist and a four-phase flow diagram. The checklist includes items deemed essential for transparent reporting of a systematic review. In this Explanation and Elaboration document, we explain the meaning and rationale for each checklist item. For each item, we include an example of good reporting and, where possible, references to relevant empirical studies and methodological literature. The PRISMA Statement, this document, and the associated Web site (http://www.prisma-statement.org/) should be helpful resources to improve reporting of systematic reviews and meta-analyses.

/pdf/the-prisma-statement-for-reporting-systematic-reviews-and-3j53e5oe33.pdf

The PRISMA Statement for Reporting Systematic Reviews and Meta-Analyses of Studies That Evaluate Health Care Interventions: Explanation and Elaboration

"The Seventh Report of the Joint National Committee on Prevention, Detection,
Evaluation, and Treatment of High Blood Pressure" provides a new guideline
for hypertension prevention and management. The following are the key messages(1) In persons older than 50 years, systolic blood pressure (BP) of
more than 140 mm Hg is a much more important cardiovascular disease
(CVD) risk factor than diastolic BP; (2) The risk of CVD, beginning at 115/75
mm Hg, doubles with each increment of 20/10 mm Hg; individuals who are normotensive
at 55 years of age have a 90% lifetime risk for developing hypertension; (3)
Individuals with a systolic BP of 120 to 139 mm Hg or a diastolic BP of 80
to 89 mm Hg should be considered as prehypertensive and require health-promoting
lifestyle modifications to prevent CVD; (4) Thiazide-type diuretics should
be used in drug treatment for most patients with uncomplicated hypertension,
either alone or combined with drugs from other classes. Certain high-risk
conditions are compelling indications for the initial use of other antihypertensive
drug classes (angiotensin-converting enzyme inhibitors, angiotensin-receptor
blockers, β-blockers, calcium channel blockers); (5) Most patients with
hypertension will require 2 or more antihypertensive medications to achieve
goal BP (<140/90 mm Hg, or <130/80 mm Hg for patients with diabetes
or chronic kidney disease); (6) If BP is more than 20/10 mm Hg above goal
BP, consideration should be given to initiating therapy with 2 agents, 1 of
which usually should be a thiazide-type diuretic; and (7) The most effective
therapy prescribed by the most careful clinician will control hypertension
only if patients are motivated. Motivation improves when patients have positive
experiences with and trust in the clinician. Empathy builds trust and is a
potent motivator. Finally, in presenting these guidelines, the committee recognizes
that the responsible physician's judgment remains paramount.

https://jamanetwork.com/journals/jama/articlepdf/196589/JSC30096.pdf

The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure: the JNC 7 report.

The Cochrane Handbook for Systematic Reviews of Interventions is the official document that describes in detail the process of preparing and maintaining Cochrane systematic reviews on the effects of healthcare interventions.

/pdf/cochrane-handbook-for-systematic-reviews-of-interventions-1xbdy6uvru.pdf

Cochrane Handbook for Systematic Reviews of Interventions

Another chapter of the antithrombin story has been written

Prasugrel STEMI subgroup analysis – Authors' reply

Respiratory difficulty after use of disopyramide.

Introduction: AF is twice as prevalent in patients with diabetes mellitus (DM) and DM is associated with increased risk of stroke, morbidity, and mortality in patients with AF. We explored outcomes by DM status and randomized anticoagulant in a large AF trial. Methods: 21,105 patients in ENGAGE AF-TIMI 48 trial were stratified into pre-specified categories: no-DM (n=13481); non-insulin dependent DM (NIDDM, n=6354); and IDDM (n=1270). We compared efficacy, safety, and net outcomes adjusted for baseline differences across the 3 groups. We assessed for effect modification by DM status on the relative efficacy and safety of edoxaban vs warfarin. The primary endpoints were stroke/SEE and ISTH major bleeding. Results: Patients with IDDM were younger (mean age 68.8 vs 69.5 vs 71.3 yrs) and had higher BMIs (32.9 vs 31.0 vs 28.4kg/m2) and CHA2DS2-VASc scores (mean 4.8 vs 4.6 vs 4.2) as compared to those with NIDDM or no-DM (each P<0.001). Patients with IDDM (adj HR 1.46, p=0.004), but not those with NIDDM (adj HR ...

Abstract 16551: Efficacy and Safety of Oral Anticoagulation in 21105 Patients With Atrial Fibrillation Stratified by Diabetic Status in the ENGAGE AF-TIMI 48 Trial

Fibrinolytic therapy has long been an important component of the treatment of patients with ST-elevation myocardial infarction (STEMI). Several new treatment strategies are currently being developed to improve the treatment of STEMI. These strategies include the development of new fibrinolytic agents that possess longer half-lives or increased fibrin specificity as compared with streptokinase or alteplase; combining fibrinolytic therapy with recently developed antiplatelet medications; and substitution of low-molecular-weight heparins or other newer thrombin inhibitors for unfractionated heparin to improve the safety, convenience and efficacy of antithrombotic therapy.

Elliott M. Antman

Papers

Another chapter of the antithrombin story has been written

Prasugrel STEMI subgroup analysis – Authors' reply

Respiratory difficulty after use of disopyramide.

Abstract 16551: Efficacy and Safety of Oral Anticoagulation in 21105 Patients With Atrial Fibrillation Stratified by Diabetic Status in the ENGAGE AF-TIMI 48 Trial

Managing ST-elevation myocardial infarction