382,703 papers found

BACKGROUND: Diabetic retinopathy (DR) is one of the serious complications of diabetes mellitus. Without further treatment, it can evolve into the stage of proliferation, which will lead to the formation of new blood vessels, vitreous hemorrhage, or anterior retinal hemorrhage, which will lead to severe vision loss and…

The results of research on a specific question differ across studies, some to a small extent and some to a large extent. Meta-analysis is a way to statistically combine and summarize the results of different studies so as to obtain a pooled or summary estimate that may better represent what is true in the population. M…

BACKGROUND: Current evidence concerning the association between persistent organic pollutants (POPs) and polycystic ovary syndrome (PCOS) is inconsistent. The aim of the present systematic review and meta-analysis is to evaluate the role of POPs in PCOS. METHODS: Databases including PubMed, Embase, Web of Science, and…

Systemic lupus erythematous (SLE) is a relatively rare disorder with prevalence rates between 5 and 50 per 100,000 population. This means performing any epidemiological analysis in a specific research center is difficult, due to the low number of cases within any one location. There is a need for biomarkers and diagnos…

Similar to other reviews within the last 4 years, a thorough review by the Royal College of Psychiatrists, published in December 2011, found that compared to delivery of an unintended pregnancy, abortion does not increase women's risk of mental health problems. In contrast, a meta-analysis published in September 2011 c…

The scientific and medical information is nowadays abundant and easily because of advances in information systems and changes in the number of research. This multiplicity requires a synthesis if one wishes to achieve a specific answer to a question. The meta-analysis is a method to perform such work by combining the re…

The recent increase in implementation of evidence-based medicine in neurosurgery has led to an increase in awareness of the importance of meta-analysis. An integral component of meta-analysis is the test of heterogeneity. This test examines whether the apparent differences between the studies are significant enough to…

OBJECTIVES: Meta-analysis allows to summarize pooled sensitivities and specificities from several primary diagnostic test accuracy studies. Often these pooled estimates are indirectly obtained from a hierarchical summary receiver operating characteristics (HSROC) analysis. This article presents a generalized linear ran…

In Red Light for Red-Light Cameras?, Alena Erke concludes that "... on the whole, redlight cameras do not seem to be a successful safety measure." Although Erke's survey of the literature appears to have been comprehensive, her review of the studies was not critical. She appears to have accepted the authors' descriptio…

Several authors have cautioned against using Fisher's z-transformation in random-effects meta-analysis of correlations, which seems to perform poorly in some situations, especially with substantial inter-study heterogeneity. Attributing this performance largely to the direct z-to-r transformation (DZRT) of Fisher z res…

The advent of genome-wide association studies has allowed considerable progress in the identification and robust replication of common gene variants that confer susceptibility to common diseases and other phenotypes of interest. These genetic effect sizes are almost invariably moderate to small in magnitude and single…

Exacerbations are a major cause of morbidity and mortality in chronic obstructive pulmonary disease. Exacerbations can be of bacterial, viral or mixed etiology, with bacteria involved in 50% of exacerbations. Consequently, current management of exacerbations frequently involves the use of antibiotics. The paper by Puha…

OBJECTIVES: We reintroduce an exact Mantel-Haenszel (MH) procedure for meta-analysis with binary endpoints which is expected to work especially well in sparse data, e.g., in meta-analyses of safety or adverse events. METHODS: The performance of the exact MH procedure in terms of empirical size and power is compared to…

One conceptualization of meta-analysis is that studies within the meta-analysis are sampled from populations with mean effect sizes that vary (random-effects models). The consequences of not applying such models and the comparison of different methods have been hotly debated. A Monte Carlo study compared the efficacy o…

The magnitude of the effect of an intervention on a quantitative outcome may be expressed as a standardized mean difference by dividing the difference in means by the standard deviation of the outcome. This is useful to compare outcomes measured using different scales, especially in meta-analysis. However, uncertainty…

The systematic review community has become increasingly aware of the importance of addressing the issues of heterogeneity and publication bias in meta-analyses. A potentially bigger threat to the validity of a meta-analysis appears relatively unnoticed. The within-study selective reporting of outcomes, defined as the s…

It is very common to find meta-analyses in which some of the studies compare 2 groups on continuous dependent variables and others compare groups on dichotomized variables. Integrating all of them in a meta-analysis requires an effect-size index in the same metric that can be applied to both types of outcomes. In this…

BACKGROUND: Meta-analysis is often considered to be a simple way to summarize the existing literature. In this paper we describe how a meta-analysis resembles a conventional study, requiring a written protocol with design elements that parallel those of a record review. METHODS: The paper provides a structure for crea…

A relevant problem in meta-analysis concerns the possible heterogeneity between trial results. If a test of heterogeneity is not significant the trials are often considered to be "homogeneous" and the individual trial results are replaced by an overall mean effect size and its confidence interval ("equal effects model"…

If the results of LIMIT-2, the two meta-analyses reviewed and the cumulative meta-analysis by Lau et al. are viewed in aggregate, there can be very little doubt regarding the beneficial effects of i.v. magnesium on mortality in suspected acute MI. The results of ISIS-4 should strengthen these odds ratios and help clari…