SEARCH · PubMed Health

Results for “Meta- analysis”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 235 records · Page 13Linked to original sources

PubMed1997

Psyllium-enriched cereals lower blood total cholesterol and LDL cholesterol, but not HDL cholesterol, in hypercholesterolemic adults: results of a meta-analysis.

We conducted a meta-analysis to determine the effect of consumption of psyllium-enriched cereal products on blood total cholesterol (TC), LDL cholesterol (LDL-C) and HDL cholesterol (HDL-C) levels and to estimate the magnitude of the effect among 404 adults with mild to moderate hypercholesterolemia (TC of 5.17-7.8 mmol/L) who consumed a low fat diet. Studies of psyllium cereals were identified by a computerized search of MEDLINE and Current Contents and by contacting United States-based food companies involved in psyllium research. Published and unpublished studies were reviewed by one author and considered eligible for inclusion in the meta-analysis if they were conducted in humans, were randomized, controlled experiments, and included a control group that ate cereal providing </=3 g soluble fiber/d. Eight published and four unpublished studies, conducted in four countries, met the criteria. Analysis of a linear model was performed, controlling for sex and age. Female subjects were divided into two groups to provide a rough estimate of the effect of menopausal status (premenopausal = <50 y, postmenopausal = >/=50 y) on blood lipids. The meta-analysis showed that subjects who consumed a psyllium cereal had lower TC and LDL-C concentrations [differences of 0.31 mmol/L (5%) and 0.35 mmol/L (9%), respectively] than subjects who ate a control cereal; HDL-C concentrations were unaffected in subjects eating psyllium cereal. There was no effect of sex, age or menopausal status on blood lipids. Results indicate that consuming a psyllium-enriched cereal as part of a low fat diet improves the blood lipid profile of hypercholesterolemic adults over that which can be achieved with a low fat diet alone.

Adult↗

PubMed2002

Meta-analysis: neither quick nor easy.

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 creating a meta-analysis protocol. Some guidelines for measurement of the quality of papers are given. A brief overview of statistical considerations is included. Four papers are reviewed as examples. The examples generally followed the guidelines we specify in reporting the studies and results, but in some of the papers there was insufficient information on the meta-analysis process. CONCLUSIONS: Meta-analysis can be a very useful method to summarize data across many studies, but it requires careful thought, planning and implementation.

Data Collection↗

PubMedDate not supplied

[Critical analysis of individual data in meta-analysis. Apropos of an experience in the domain of drug treatment in arterial hypertension].

Reliable syntheses are more and more needed by physicians. In the therapeutic field, this need is illustrated by the growing number of syntheses using meta-analysis tools. Some of these syntheses are based on individual patient data, and this offers three kinds of advantages: the favourable consequences of a collaborative approach, the enhancement of data reliability, and a more complete extraction of useful information thanks to wider analysis potential. Most often, achieving the first two advantages does not require the individual patient data to be available, and a wider analysis potential seems to be the major rationale of such an approach. For instance, the assessment of the variation of treatment effect with along time is more accurate, but may also raise doubts about the validity of some hypotheses, for example, those underlying classical analysis techniques, or at the basis of even acknowledged pathophysiological theory. Ultimately, the concepts of identifying responders (here defined in terms of quantity or quality of life) and identifying the therapy target population are concretely applied in a way that will affect classical medical practice. Tomorrow, drugs will not be prescribed to a hypertensive individual because of the blood pressure level, but considering the size of the predicted therapeutic benefit.

Humans↗

PubMed2003

Comparison of outcomes (early and six- month) of direct stenting with conventional stenting (a meta-analysis of ten randomized trials).

Although direct stenting (DS) is increasingly used in clinical practice instead of stent implantation after predilatation (conventional stenting [CS]), its impact has not been scientifically proved. We therefore performed, using Mantel-Haenszel analysis, a meta-analysis of the published randomized studies comparing DS with CS. Furthermore, all the key procedural data were systematically sought out and pooled. Ten trials (2,650 coronary lesions, 2,576 patients) were identified and entered into the analysis. Adopted angiographic exclusion criteria were homogeneous. DS, compared with CS, was found to have a similar success rate (98.7% vs 98.9%) and no specific complications. Across the studies, the mean rate of crossover to predilatation in the DS arm was 5.9%. Overall, DS was associated with a 17% procedural time (95% confidence interval [CI] 14% to 20%), a 18% fluoroscopic time (95% CI 15% to 21%), a 11% contrast volume (95% CI 9% to 14%), and a 22% cost reduction (95% CI 16% to 28%). In the early postintervention period, DS was associated with a trend toward reduction of each of the major adverse events (MACEs) and with a significant reduction of myocardial infarction (MI) + death (odds ratio [OR] 0.57, 95% CI 0.35 to 0.95). However, at 6 months, the OR (95% CI) for death, MI, target lesion revascularization, and MACEs were 0.47 (0.19 to 1.27), 0.72 (0.45 to 1.25), 1.07 (0.77 to 1.46), and 0.82 (0.63 to 1.08), respectively. In the subgroup of studies providing quantitative angiographic data, all the parameters were found to be similar between the CS and DS groups. In conclusion, the present meta-analysis shows that DS compared with CS, in selected coronary lesions, is safe, optimizes equipment use, and may enhance the early results of coronary interventions while warranting similar late clinical outcomes.

Blood Vessel Prosthesis Implantation↗

PubMed1994

Cigarette smoking and sperm density: a meta-analysis.

OBJECTIVE: To quantify, through meta-analysis techniques, the association between cigarette smoking and sperm density. METHODS: The logarithm of the ratio of mean sperm density for smokers to that for nonsmokers for the studies included in this meta-analysis was regressed against a constant, an indicator of study population source (infertility clinic patients or normal men), minimum number of cigarettes smoked per day among smokers (< 10, > or = 10), exclusion of azoospermic men (yes/no), number of semen specimens analyzed (one versus two), and blinding of laboratory personnel to the smoking status of the study participants (yes/no). Regression analyses were performed both unweighted and weighted inversely by study size. A qualitative and quantitative assessment of the relationship between the numbers of cigarettes smoked per day and sperm density was performed. RESULTS: Results of the meta-analysis indicate that smokers' sperm density is on average 13% to 17% (95% confidence interval = 8.0, 21.5) lower than that of nonsmokers. No other factors besides cigarette smoking were found to be independent predictors of sperm density. No clear dose-response relationships between the numbers of cigarettes smoked per day and sperm density emerged. Research conducted by the authors supports the findings of the meta-analysis. CONCLUSION: Cigarette smoking is associated with lowered sperm density. The inconsistency in the literature with regard to this conclusion appears to be the result of small sample sizes in most studies.

Adult↗

PubMed2000

Meta-analysis in otolaryngology.

OBJECTIVE: To examine the results of meta-analyses in otolaryngology and compare these results with the individual component studies that constitute each meta-analysis. DESIGN: A retrospective review of the literature. MAIN OUTCOME MEASURES: Studies that conducted pooled statistical systematic analyses indexed on MEDLINE for the 10-year period from January 1989 to January 1999 were selected for keyword or subject headings of meta-analysis and otolaryngology (N = 22). Analysis consisted of a modified funnel graph depiction of the individual studies that made up each meta-analysis. Each meta-analysis was evaluated for consistency among these individual studies and comparison of the median result with the weighted mean meta-analysis result. In addition, the methodologic quality of each meta-analysis was assessed in terms of the rigor with which component studies were evaluated. RESULTS: Ten (46%) of the 22 meta-analyses did not provide the individual study results that made up their meta-analyses. The results of 10 studies (46%) were similar to the median result of their individual component studies. The results of 2 studies (9%) differed from this median result, with widely heterogeneous component study results. CONCLUSIONS: A large proportion of meta-analyses in otolaryngology (46%) fail to provide the individual study results necessary to analyze the meta-analysis result critically. Most remaining studies do provide results that accurately compare with the median of their component study results. Only a small proportion of meta-analyses were found to have disparate results, and each appropriately discusses the heterogeneity of the individual studies that comprise their meta-analysis.

Evaluation Studies as Topic↗

PubMed2002

A comparison of summary patient-level covariates in meta-regression with individual patient data meta-analysis.

OBJECTIVES: To compare meta-analysis of summary study level data with the equivalent individual patient data (IPD) analysis when interest lies in identification of binary patient characteristics related to treatment efficacy. DESIGN: A simulation study comparing meta-regression with IPD analyses of randomized controlled trials. METHODS: Twenty-seven different meta-analysis situations were simulated with 1000 repetitions in each case. The following parameters were varied: (1) the treatment effect magnitude for different patient risk groups; (2) sample sizes of individual studies; and (3) number of studies. The meta-regression and IPD results were then compared for each situation. RESULTS: The statistical power of meta-regression was dramatically and consistently lower than that of IPD analysis, with little agreement between the parameter estimates obtained from the two methods. Only in meta-analyses of large numbers of large trials, did meta-regression detect differential treatment effects between risk groups with any consistency. CONCLUSIONS: Meta-analysis of summary data may be adequate when estimating a single pooled treatment effect or investigating study level characteristics. However, when interest lies in investigating whether patient characteristics are related to treatment, IPD analysis will generally be necessary to discover any such relationships. In these situations practitioners should try to obtain individual-level data.

Humans↗

PubMed1988

Dipyridamole in the treatment of angina pectoris: a meta-analysis.

A meta-analysis was performed to reevaluate the efficacy of dipyridamole for prophylaxis of angina pectoris. We found 10 articles that reported 11 randomized control trials published between 1960 and 1970. Three trials found a statistically significant benefit for the drug vs placebo, four showed a positive trend, two found no difference, and two showed a slight trend favoring placebo. When the results of all 11 trials were combined, two different statistical methods showed a statistically significant benefit from the drug. These combined results must be interpreted cautiously because of excluded patients and other methodologic variations in the studies, as well as evidence from other studies that dipyridamole may aggravate angina. Nevertheless, we conclude that there is some evidence for efficacy of the drug and believe the question should be restudied in larger and better-designed trials.

Angina Pectoris↗

PubMed1986

The dissemination of research findings: some limitations revealed when attempting a meta-analysis.

A meta-analysis of the literature on drug treatments for Alzheimer's disease revealed the following limitations in the dissemination of research findings: multiple publication of findings, failure to report basic descriptive statistics and failure to respond to written requests for additional information on the research. The possible reasons for these problems and remedies for them are discussed.

Alzheimer Disease↗

PubMedDate not supplied

Effect of preoperative instruction on postoperative outcomes: a meta-analysis.

A meta-analysis was performed on 68 studies to examine the effect of preoperative instruction on postoperative outcomes. The 68 studies represented 2,413 experimental subjects and 1,605 control group subjects and yielded 423 individual effect sizes. The 423 individual effect sizes had a mean effect size of 0.44 and a variance of 2.43. The mean effect size indicated that, in terms of postoperative outcomes, an average patient who received preoperative instruction was at the 66th percentile of a similar group of patients who did not receive preoperative instruction. The accompanying large variance indicated this finding was not consistent across subject-studies. Substantive characteristics of subject-studies used to categorize effect size were: type of content, method of organization, type of presentation, level of patients' fear/anxiety, and types of outcomes measured. All categories analyzed had positive effect sizes. Within categories of content, psychological and mixed forms of content produced the lowest variances. Categories of organization and presentation did not produce data to demonstrate a clear difference in the levels analyzed. Categories of patient fear/anxiety indicated that the greatest effects were achieved with patients who had high levels of fear/anxiety, followed by moderate levels and low levels. The most consistent results were found with moderate levels of fear/anxiety. When categorized by types of outcomes measured, all effect sizes remained positive. The variances accompanying each effect size remained relatively substantial at all levels of aggregation, with small variances found only at the greatest level of specificity.(ABSTRACT TRUNCATED AT 250 WORDS)

Anxiety↗

PubMed1987

Meta-analysis in clinical research.

Meta-analysis is the process of combining study results that can be used to draw conclusions about therapeutic effectiveness or to plan new studies. We review important design and statistical issues of this process. The design issues include protocol development, objectives, literature search, publication bias, measures of study outcomes, and quality of the data. The statistical issues include consistency (homogeneity) of study outcomes, and techniques for pooling results from several studies. Guidelines are provided to assess the quality of meta-analyses based on our discussion of the design and statistical issues. Limitations and areas for further development of this approach are discussed; researchers should come to a general agreement on how to conduct meta-analysis. As an explicit strategy for summarizing results, meta-analysis may help clinicians and researchers better understand the findings of clinical studies.

Data Collection↗

PubMed1997

Meta-analysis and endocrinology.

It is likely that more studies that use meta-analysis will be published in the endocrinologic literature. Major strengths of meta-analysis are the systematic ascertainment of research on a given topic and the explicit delineation of reasons for accepting or rejecting studies as a basis for drawing conclusions. The tendency of meta-analysis to focus on a single estimate of effect and to ignore heterogeneity are problems both with the conduct of meta-analysis and the way in which it is interpreted. Meta-analysis cannot overcome bias in the original studies. It is difficult to perform a good meta-analysis and easy to perform a bad one. The critical reader should not be overawed by the results of a meta-analysis. Reading a meta-analysis should not substitute for careful reading of the primary studies on which the meta-analysis is based. Meta-analysis should not be used to stifle the conduct of original research.

Bias↗

PubMed1997

Current controversies in the application of meta-analysis (with special reference to oncological treatments)

Meta-analysis was proposed more than 20 years ago as an innovative technique for pooling the results of a series of clinical studies. This technique has a two-fold purpose: i) to retrieve pertinent clinical information without introducing selection biases; ii) to combine these clinical data obtained from different sources into a single synthetic index that summarises all available information. This review highlights the current perspectives in the application of meta-analysis and places particular emphasis on discussing the limitations of this technique that have been identified in recent years. Specific controversies in this area include: i) comparison between meta-analysis of the literature and meta-analysis of individual patient data; ii) heterogeneity of the clinical material introduced in the meta-analytic pooling; and iii) survival meta-analysis as a method for pooling long-term outcome data. After debating these three controversial points, this review examines the newest uses of meta-analysis that have been proposed for the evaluation of cost-effectiveness data and tries to identify the meta-analytic applications that will probably be expanded in the near future as opposed to those that will instead be developed less and less.

Clinical Trials as Topic↗

PubMed2000

Adverse drug reactions in hospitalized patients: A critique of a meta-analysis.

OBJECTIVE: To replicate and to critique a recently published meta-analysis[1] of the incidence of nonpreventable serious and fatal adverse drug reactions (ADRs) in hospitalized patients, to better understand its results and conclusions. METHODS: The published methods described in the meta-analysis of Lazarou and colleagues were followed.[1] This meta-analysis reviewed 30 original publications describing 39 prospective studies. In each study, the numbers of patients with nonpreventable ADRs, probably or definitely related to drugs, were sought to allow calculation of the incidence of "all-severities," serious and fatal, ADRs. In the original meta-analysis, these ADR incidences were then pooled to provide estimates of the incidence in all hospitalized patients. In our analysis, the original studies were examined by 2 investigators for consistency with the study search and inclusion criteria of the meta-analysis by Lazarou and colleagues, as well as accuracy and appropriateness of data extraction, meta-analysis, and conclusions. RESULTS: Multiple sources of heterogeneity among studies and data were found and include important differences in populations and hospital wards monitored, surveillance techniques, ADR definitions, determination of preventability of ADRs, distinguishing relationship to drugs, and in formats of reporting ADRs (by numbers of events or by patients). Imputations of event numerators made by the authors of the original meta-analysis were questionable and may overestimate the results of any individual study. With regard to fatal ADRs, the problem of small numbers of events is likely to introduce large errors in incidence estimates. Simple pooling of fatal event frequencies from only those studies specifically reporting the number of fatal ADRs, as was done in the meta-analysis of Lazarou and colleagues, is likely to dramatically overestimate the death rate. CONCLUSION: Meta-analysis was invalid because of heterogeneity of the studies. Most of these studies did not report the data needed for incidence calculations. The methodology used was seriously flawed, and no conclusions regarding ADR incidence rates in the hospitalized population in the United States should be made on the basis of the original meta-analysis.

Cause of Death↗

PubMedDate not supplied

[Meta-analysis of therapeutic trials: applications in psychiatry].

Meta-analysis is being increasingly used in therapeutic and clinical research to synthetize data from terminated clinical trials. Meta-analysis provides a powerful tool to objectively combine data in a quantitative manner, unlike the classical general review of literature, which is qualitative and subjective by definition, and thus not reproducible, and also the simple data pooling, methods which neglects the statistical heterogeneity between studies. The two most known objectives of meta-analysis are, to provide an objective decision when the trial results have produced contradictory or non-significant results, and to give a better estimation of the magnitude of the treatment effect. Precise methodological rules must be followed, but these rules are not known well enough in the scientific community. For example, particular care is necessary for the retrieval and selection of the trials: all available trials which satisfy predefined criteria of methodological validity should be taken into consideration. One of the main pitfalls in meta-analysis is the problem of unpublished trials, which represents a potential bias seen as an overestimation of treatment effect. In psychiatry, the applications of meta-analysis are numerous, especially in the domain of the treatment of depressive disorders, which will be developed in this paper. Several meta-analyses have been performed to assess the efficacy of antidepressants in major depression, especially with the "new antidepressants", which include the specific serotonine reuptake inhibitors (SSRIs). To date, these meta-analyses have shown that the main advantage of SSRIs was that they were better accepted, but without being more efficacious compared with classic antidepressants. The results of several of these meta-analyses are to be interpreted with the potential biases in mind, especially the publication bias and selection bias. Clinicians must be aware of the difficulties encountered in the choice of outcome criteria, and in deciding how to deal with patients that withdraw from treatment early (intention to treat analysis is the least biased solution for this problem.). Meta-analysis can therefore be helpful in establishing medical references in psychiatry, and to organize consensus conferences, but the limits of this method must be clearly recognized.

Antidepressive Agents, Second-Generation↗

PubMed1999

Promises and pitfalls of meta-analysis in vaccine research.

Meta-analysis continues to grow in usage despite increased concern regarding its soundness. Over twenty meta-analyses directly pertain to vaccines. Vaccine researchers need to understand the technique as well as the criticisms. Meta-analysis involves four steps. First, the meta-analyst should establish certain criteria in advance of the second step where the meta-analyst gathers the data--the results of the individual studies. Third, the meta-analyst assesses the individual studies for combinability and, fourth, the meta-analyst actually combines the data to generate conclusions. Vaccine meta-analyses have addressed a variety of vaccines and a variety of study objectives including efficacy, immunogenicity and safety. Three classical concerns revolve around the issue of publication bias, data dredging and individual study variability. Additionally, vaccine meta-analyses suffer concerns particular to the field of vaccine research.

Animals↗

PubMed1990

The impact of methodological factors on child psychotherapy outcome research: a meta-analysis for researchers.

Two recent meta-analyses have generated evidence for child and adolescent psychotherapy effects. However, critics note that such meta-analyses often include studies with methodological shortcomings which might invalidate their results. In the present study, we explored whether the results of the most extensive child/adolescent meta-analysis might have been influenced by such methodological variables, focusing on internal validity and external validity factors. Together, these factors accounted for two-thirds as much variance as the substantive factors (e.g., type of therapy, age) in the original meta-analysis. This suggests that relative to these therapy and child-characteristic variables, methodological factors have a substantial, though smaller, impact on meta-analysis results. In general, increased experimental rigor was related to larger effect sizes; this argues against the hypothesis that methodologically weak studies have led to an overestimate of therapy effects. No significant interactive relations were found between validity factors and predictors of outcome; this suggests that the relations noted in previous meta-analyses between outcome and various variables were not distorted by the validity factors tested here.

Adaptation, Psychological↗

PubMed2003

[Clinical decision-making: systematic reviews and meta-analysis].

Randomized clinical trials and mainly meta-analysis, have become the gold standard in the assessment of drug efficacy. A meta-analysis is a systematic review that uses statistical techniques to combine and summarize results of previous studies. Thereby, their design helps to identify and explain inconsistencies in the results of previous studies. One of the most complex and valid designs consists in obtaining the original database for each study (published or not) performing a < > or meta-analysis of individualized patient data. This type of meta-analysis avoids the partiality which may originate from the non-publication of nonsignificant studies. The future tendency would recommend that investigators, clinicians, reviewers, journal editors and sponsors agree on publication criteria other than positive p values such as clinical validity and clinical relevance.

Clinical Trials as Topic↗