Showing papers on "Publication bias published in 1995"

Misleading meta-analysis

Abstract: A meta-analysis of treatments in myocardial infarction published in 1992 retrospectively showed that streptokinase was associated with a highly significant fall in mortality by 1977, after inclusion of 15 trials.1 Thrombolysis was, however, not widely recommended until 10 years later—after the effect was confirmed in two mega trials.1 2 3 In the case of magnesium, a substantial fall in mortality was evident by 1990, after inclusion of seven trials. In 1993, based on an updated meta-analysis it was argued that magnesium treatment represented an “effective, safe, simple and inexpensive” intervention that should be introduced into clinical practice without further delay.4 The negative results of ISIS 4 (the fourth international study of infarct survival), published in last week's Lancet,5 have dealt a blow to enthusiasm for both magnesium and meta-analysis.6 As the findings of meta-analyses and systematic reviews are generally not tested in mega trials the situation regarding magnesium represents an opportunity to examine a false positive meta-analysis. The table compares the meta-analyses of trials of magnesium and streptokinase after myocardial infarction. Trials were cumulatively included until the treatment effect was significant at P<0.001. For magnesium, seven small trials whose results were published in the 1980s were sufficient to establish the effect. Although trials were larger in the case of fibrinolytic treatment, twice as many studies and two decades were necessary to reach the same level of significance. Until recently it could …

Publication decisions revisited: the effect of the outcome of statistical tests on the decision to publish and vice versa

Abstract: This article presents evidence that published results of scientific investigations are not a representative sample of results of all scientific studies. Research studies from 11 major journals demonstrate the existence of biases that favor studies that observe effects that, on statistical evaluation, have a low probability of erroneously rejecting the so-called null hypothesis (H 0). This practice makes the probability of erroneously rejecting H 0 different for the reader than for the investigator. It introduces two biases in the interpretation of the scientific literature: one due to multiple repetition of studies with false hypothesis, and one due to failure to publish smaller and less significant outcomes of tests of a true hypotheses. These practices distort the results of literature surveys and of meta-analyses. These results also indicate that practice leading to publication bias have not changed over a period of 30 years.

A general linear model for estimating effect size in the presence of publication bias

Abstract: When the process of publication favors studies with smallp-values, and hence large effect estimates, combined estimates from many studies may be biased. This paper describes a model for estimation of effect size when there is selection based on one-tailedp-values. The model employs the method of maximum likelihood in the context of a mixed (fixed and random) effects general linear model for effect sizes. It offers a test for the presence of publication bias, and corrected estimates of the parameters of the linear model for effect magnitude. The model is illustrated using a well-known data set on the benefits of psychotherapy.

Glucocorticoids are ineffective in alcoholic hepatitis: a meta-analysis adjusting for confounding variables.

Abstract: The aim of this study was to perform a meta-analysis of controlled clinical trials of glucocorticoid treatment in clinical alcoholic hepatitis, adjusting for prognostic variables and their possible interaction with therapy, because these trials have given appreciably different results. Weighted logistic regression analysis was applied using the summarised descriptive data (for example, % with encephalopathy, mean bilirubin value) of the treatment and control groups of 12 controlled trials that gave this information. Despite evidence of publication bias favouring glucocorticoid treatment, its overall effect on mortality was not statistically significant (p = 0.20)--the relative risk (steroid/control) was 0.78 (95% confidence intervals 0.51, 1.18). There was indication of interaction between glucocorticoid therapy and gender, but not encephalopathy. Thus, the effect of glucocorticoid treatment may be different (beneficial or harmful) in special patient subgroups. These results do not support the routine use of glucocorticoids in patients with alcoholic hepatitis, including those with encephalopathy. Whether other subgroups may benefit needs further investigation using the individual patient data from the published trials and testing in new randomised trials.

Dyspepsia—How Noisy Are Gallstones? A Meta-Analysis of Epidemiologic Studies of Biliary Pain, Dyspeptic Symptoms, and Food Intolerance

Abstract: Background: In contrast to earlier beliefs, it is nowadays assumed that no relation exists between dyspeptic symptoms and the presence of gallstones. Although many studies indeed failed to show a relation, each has been too small to exclude it. The aim of this meta-analysis is to systematically review epidemiologic studies and to synthesize the data. Methods: Twenty-one controlled studies on the association between gallstones and dyspeptic symptoms were analyzed after critical appraisal with regard to selection bias, blinding, confounding, and data presentation. Most of them had reasonable validity. Inconsistencies between results of the studies could not be explained by differences in study design or validity. There was a slight indication of publication bias. Results: Upper abdominal pain was consistently associated with gallstones (pooled odds ratios, about 2.0), with no preference for the right side. The findings on biliary pain were inconsistent. The results exclude with reasonable certainty an assoc...

The impact of method choice on meta‐analysis

Abstract: Summary This paper focusses mainly on three crucial choices identified in recent meta-analyses, namely (a) the effect of using approximate statistical techniques rather than exact methods, (fa) the effect of using fixed or random effect models, and (c) the effect of publication bias on the meta-analysis result. The paper considers their impact on a set of over thirty studies of passive smoking and lung cancer in non-smokers, and addresses other issues such as the role of study comparability, the choice of raw or adjusted data when using published summary statistics, and the effect of biases such as misclassification of subjects and study quality. The paper concludes that, at least in this example, different conclusions might be drawn from metaanalyses based on fixed or random effect models; that exact methods might increase estimated confidence interval widths by 5–20% over standard approximate (logit and Mantel-Haenszel) methods, and that these methods themselves differ by this order of magnitude; that taking study quality into account changes some results, and also improves homogeneity; that the use of unadjusted or author-adjusted data makes limited difference; that there appears to be obvious publication bias favouring observed raised relative risks; and that the choice of studies for inclusion is the single most critical choice made by the modeller.

Review of the efficacy and effectiveness of adaptive seating for children with cerebral palsy.

Abstract: The purpose of this article is to review the published research evidence for the efficacy and effectiveness of adaptive seating in the management of children with cerebral palsy. This review is undertaken to determine whether adaptive seating outcomes proposed in the clinical literature have been substantiated. The literature search was confined to English-language publications between 1982 and 1994. Thirty-seven research studies were identified through: 1) on-line search of Index Medicus, Cumulative Index to Nursing and Allied Health Literature, and Psychological Abstracts; 2) scanning conference proceedings and article reference lists; and, 3) tracking of author citations through the Science Citations Index. Eight studies met the selection criteria of using subjects who were children with cerebral palsy, including adaptive seating as an independent variable, and including an unsupported sitting comparison condition. Study quality was evaluated using an adaptation of Sackett's validity criteria. Sackett's classification system was utilized to identify levels of evidence and to grade recommendations. Grade A, B, and C recommendations were generated from Level I to Level V evidence for some of the clinically proposed seating outcomes. Additional seating research is required to strengthen the recommendations and investigate unexplored outcomes. Limitations of the review are potential reviewer and publication bias.

Review of the Reviewer

Abstract: Reviewers can disagree substantially when evaluating the same materials. For papers submitted to an editorial board, the Editor-in-Chief can suggest compromises. However, this is not the case in the normal abstract grading procedures for large meetings. If important discrepancies arise between reviewers, a review committee may propose corrective measures. However, this is only feasible for smaller meetings with a limited number of abstract submissions. In this study, when reviewing the same abstracts, a statistically significant correlation between reviewers was present in 15 instances and absent in 13 others. It would appear that some review of the reviewer is highly desirable and may prevent publication bias.