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PubMed1993

Meta-analysis of the literature or of individual patient data: is there a difference?

The use of meta-analyses or overviews to combine formally the results of related randomised clinical trials is becoming increasingly common. However the distinction between analyses based on information extracted from the published literature and those based on collecting and reanalysing updated individual patient data is not clear. We have investigated the difference between meta-analysis of the literature (MAL) and meta-analysis of individual patient data (MAP) by comparing the two approaches using randomised trials of cisplatin-based therapy in ovarian cancer. The MAL was based on 788 patients and the MAP on 1329 and estimated median follow-ups were 3.5 and 6.5 years, respectively. The MAL gave a result of greater statistical significance (p = 0.027 vs p = 0.30) and an estimate of absolute treatment effect three times as large as the MAP (7.5% vs 2.5%). Publication bias, patient exclusion, length of follow-up, and method of analysis all contributed to this observed difference. The results of a meta-analysis of the literature alone may be misleading. Whenever possible, a meta-analysis of updated individual patient data should be done because this provides the least biased and most reliable means of addressing questions that have not been satisfactorily resolved by individual clinical trials.

Antineoplastic Agents↗

PubMedDate not supplied

The time to onset and overall analgesic efficacy of rofecoxib 50 mg: a meta-analysis of 13 randomized clinical trials.

OBJECTIVE: To determine the time to onset of analgesia of rofecoxib based on a patient-level meta-analysis of randomized, placebo-controlled, postoperative oral surgery pain studies. METHODS: A search on MEDLINE and of Merck data on file was conducted to identify studies that met the inclusion criteria. Meta-analysis inclusion criteria required that patients were treated with a single oral dose of rofecoxib 50 mg when they experienced moderate or severe pain after surgical extraction of > or = 2 third molars; study design involved patient randomization, double-blinding, and matching placebo, and onset data from individual patients were available. The meta-analysis of time to onset also required that studies used the two-stopwatch method. Eleven studies fulfilled the onset criteria and included patients who received a single dose of rofecoxib 50 mg (N = 1220) or placebo (N = 483). These studies were analyzed to determine time to onset of analgesia, time to perceptible pain relief, percentage of patients achieving onset of analgesia, and duration of analgesia. Six of the 11 studies included a nonselective nonsteroidal anti-inflammatory drug (N = 303) and were included in the onset meta-analysis for comparison. The meta-analysis of overall efficacy also required that data on total pain relief scores over 8 hours were available. Over-all effectiveness of analgesia was based on analysis of 13 studies involving 1330 rofecoxib patients and 570 placebo patients on the endpoints of total pain relief scores over 8 hours and patient global assessment of response to therapy at 24 hours. Eight of the 13 studies with a nonselective nonsteroidal anti-inflammatory drug comparator (N = 391) were included for the efficacy meta-analysis. RESULTS: Patient demographics and baseline characteristics were similar across treatment groups in each study. Median time to onset of analgesia for rofecoxib was 34 minutes (95% CI, 31-38 minutes), significantly faster than placebo, which did not achieve onset within the 4 hours the assessment was conducted (P < 0.001). Duration of analgesia for rofecoxib 50 mg was > 24 hours. Rofecoxib achieved a greater mean total pain relief score over 8 hours than placebo (17.4 versus 4.4; P < 0.001) and a greater patient response rate on patient global assessment of response to therapy at 24 hours than placebo (73% versus 16%; P < 0.001). Outcomes were similar between the rofecoxib group and the nonselective nonsteroidal anti-inflammatory drug group. CONCLUSION: In this meta-analysis of over 1200 rofecoxib-treated patients, a single dose of rofecoxib 50 mg demonstrated a rapid onset of analgesia in approximately half an hour combined with sustained effectiveness, supporting its use as a treatment of acute pain.

Adolescent↗

PubMed2006

Assessing the amount of heterogeneity in random-effects meta-analysis.

In a random-effects meta-analysis, a new confidence interval for the heterogeneity parameter is proposed. With this interval, the amount of heterogeneity in a meta-analysis can be assessed so that it can be judged whether the pooling of the estimates is meaningful. Through suitable corrections of the lower bound, based on the treatment effect measure of interest, the resulting interval yields satisfactory results with respect to the predefined confidence coefficient. Lower and upper bound of the interval can be used for one-sided hypothesis testing on the amount of the underlying between-trial variability.

Analysis of Variance↗

PubMed1992

Prophylactic antibiotics for the prevention of infectious complications including empyema following tube thoracostomy for trauma: results of meta-analysis.

Since 1977, six clinical trials have been performed on the subject of routine antibiotic prophylaxis in patients requiring tube thoracostomy for trauma. No definitive conclusions have been reached regarding the efficacy of antibiotic use in this setting. The results of these clinical trials were pooled to generate an unbiased estimate of the efficacy of antibiotic prophylaxis for tube thoracostomy using the technique of meta-analysis. Meta-analysis is a statistical method for synthesizing results from separate but similar experiments, grouping them, and comparing each to the null hypothesis. Meta-analysis allows synthesis of all of the available data on antibiotic prophylaxis for tube thoracostomy to resolve the controversy surrounding this issue generated by different but similar clinical studies with conflicting results. Despite different conclusions of value when taken individually, the combined analysis does not support the null hypothesis (no effect of antibiotics). The statistical method is highly significant despite different mechanisms of injury, pathologic findings, and antibiotics employed.

Anti-Bacterial Agents↗

PubMed1999

A note on issues in meta-analysis for behavioral genetic studies using categorical phenotypes.

Meta-analysis of behavioral genetic studies would provide (i) tighter confidence intervals around parameter estimates, (ii) clarification of apparently discrepant study findings, and (iii) a mechanism for analyzing systematic causes of between-study differences. We examined some key issues that arise in the meta-analysis of categorical phenotypes. Data were simulated under a multifactorial threshold model that assumed an underlying normal liability distribution, and summary statistics (probandwise concordance rate, recurrence risk ratio, odds ratio, kappa) compared for given values of the liability correlation between relatives and given population prevalence. Although the odds ratio and kappa statistic performed well at moderate to high values of the population prevalence (15-50%), at low values all of these statistics were sensitive to overall prevalence. In cases where the assumption of a multifactorial threshold model is reasonable, direct estimation of genetic and environmental parameters from the summary statistics from all studies appears to be a preferable strategy. For cases where data from non-randomly ascertained samples are used, the impact of misspecification of the model for ascertainment was examined. For some parameter values, such misspecifications led to quite serious biases to estimates of genetic and environmental parameters. These biases varied in complex ways as a function of research design and of the true causes of variation in the population, so that the same misspecification could lead to an overestimate of the importance of genetic influences in twin data but an underestimation in adoption data or to an overestimate of the importance of genetic effects from twin data if shared environmental as well as genetic influences were simulated but an underestimate of genetic effects if shared environmental effects were assumed unimportant. These complexities emphasize the importance of being sensitive to the effects of misspecifying ascertainment corrections in any meta-analysis of behavioral genetic data.

Confidence Intervals↗

PubMed2002

Noninvasive ventilation in acute respiratory failure--a meta-analysis update.

OBJECTIVE: To present a meta-analytic update on the effects of noninvasive ventilation (NIV) in the management of acute respiratory failure. DESIGN: Meta-analysis of randomized controlled clinical trials in acute respiratory failure comparing NIV with standard medical therapy. PATIENTS: Randomized controlled trials of NIV in acute respiratory failure were identified by search of i) MEDLINE (1966-2000), ii) published abstracts from scientific meetings, and iii) bibliographies of relevant articles. MEASUREMENTS AND MAIN RESULTS: Of the 15 randomized controlled trials that were identified (13 published and 2 in abstract form), 8 studies were on exacerbations of chronic obstructive pulmonary disease (COPD) and 7 on diverse disease processes in both COPD and non-COPD groups ("mixed-group"). Because of underlying heterogeneity of treatment effects, only the DerSimonian-Laird random effects estimator was used and reported. The effects of NIV vs. standard therapy on mortality and subsequent invasive mechanical ventilation (MV) was assessed as risk difference, and hospital length of stay as mean weighted difference (days). NIV was associated with reduction in mortality (8%, p = .03), reduced need for MV (19%, p = .001) and shortened hospital length of stay (2.74 days, p = .004). In the COPD cohort, significant reductions in mortality (13%, p = .001), need for MV (18%, p = .02), and hospital length of stay (5.66 days, p = .01) were observed in the group treated with NIV. In contrast, in the mixed-group, there was no demonstrable reduction in mortality (0%, p = .98). However, there was significant reduction in the need for MV (22%, p = .001). Publication bias was not evident on analysis. Treatment effect i) as mortality or need for mechanical ventilation was not modified by enrollment pH, PaCO2, nor age and ii) was not related (as log odds ratio) to underlying risk (control arm log odds). Cumulative meta-analysis did not demonstrate any substantial variation in the point estimates with the addition of the recently published studies. However a contraction in the confidence intervals was observed in the COPD subgroup. Complication rates were not significantly different in the standard medical therapy group and the NIV treated patients. CONCLUSION: Substantial reductions in mortality and the need for subsequent MV were associated with NIV in acute respiratory failure, especially in the COPD subgroup. Hospital length of stay was variably affected. Heterogeneity of treatment effects was observed.

Acute Disease↗

PubMed2006

Meta-analysis in neuropsychology: basic approaches, findings, and applications.

This article is a broad review of the approaches, findings, and applications of meta-analyses on clinical neuropsychological topics. The review is divided into four sections: basic characteristics of meta-analysis; the value of meta-analysis for neuropsychological investigations; illustrative findings from various meta-analyses on neuropsychological topics demonstrating the type of questions that can be answered; and problems and limitations of meta-analysis with a focus on future directions. The article is not intended to exhaustively review all the relevant literature nor detail the technical aspects of meta-analytic techniques, but rather it is designed to provide a basic, conceptual introduction for the general reader, particularly the clinician, to aid in comprehension of the now burgeoning literature that uses meta-analysis. Throughout, illustrative examples are developed and references are made to the practice of clinical neuropsychology.

Humans↗

PubMed1985

Meta-analysis: quantitative integration of independent research results.

Meta-analysis, a quantitative method of combining the results of independent research studies, is described as a method for reviewing research literature. Four steps are taken to summarize the research in an area. First, a thorough literature review is conducted to identify a group of research studies with the relevant treatment variable. Second, an effect size is calculated for each study. Third, an overall (composite) effect size is determined by a weighted combination of the obtained effect sizes. Fourth, a fail-safe N (the number of unpublished studies with opposing conclusions needed to negate the published literature) is calculated to assess the certainty of the overall effect size. Meta-analysis was applied to 33 studies of chymopapain in an illustrative example. The analysis produced a large effect size of 0.8082 and a fail-safe N of 214, indicating strong support for the effectiveness of the treatment with chymopapain. Meta-analysis can be a useful tool if it is used properly. It is particularly useful as an adjunct to other methods of review that are used in pharmacy practice.

Chymopapain↗

PubMed2005

The file-drawer problem revisited: a general weighted method for calculating fail-safe numbers in meta-analysis.

Quantitative literature reviews such as meta-analysis are becoming common in evolutionary biology but may be strongly affected by publication biases. Using fail-safe numbers is a quick way to estimate whether publication bias is likely to be a problem for a specific study. However, previously suggested fail-safe calculations are unweighted and are not based on the framework in which most meta-analyses are performed. A general, weighted fail-safe calculation, grounded in the meta-analysis framework, applicable to both fixed- and random-effects models, is proposed. Recent meta-analyses published in Evolution are used for illustration.

Meta-Analysis as Topic↗

PubMed2001

Effectiveness of second-generation antipsychotics in patients with treatment-resistant schizophrenia: a review and meta-analysis of randomized trials.

OBJECTIVE: The authors conducted a review and meta-analysis of studies that compared the efficacy and tolerability of typical and second-generation antipsychotics for patients with treatment-resistant schizophrenia. METHOD: A systematic search revealed 12 controlled studies (involving 1,916 independent patients), which were included in the review. For the seven studies that compared clozapine to a typical antipsychotic, a meta-analysis was performed to examine clozapine's effects on overall psychopathology, response rate, extrapyramidal symptoms, and tardive dyskinesia. RESULTS: The meta-analysis confirmed that treatment-resistant schizophrenic patients have more favorable outcomes when treated with clozapine rather than a typical antipsychotic, as reflected by Brief Psychiatric Rating Scale total score, categorical response rate, Scale for the Assessment of Negative Symptoms score, Simpson-Angus Rating Scale score, and compliance rate. Clozapine also conferred benefits on the sickest treatment-resistant schizophrenic patients. Patients treated with olanzapine also had more favorable outcomes with regard to categorical response and compliance rates. CONCLUSIONS: In the aggregate, the results of a meta-analysis indicated that clozapine exhibits superiority over typical antipsychotics in terms of both efficacy (as measured by improvement in overall psychopathology) and safety (in terms of reduced extrapyramidal side effects). However, the magnitude of the clozapine treatment effect was not consistently robust. Efficacy data for other second-generation antipsychotics in the treatment of patients with refractory schizophrenia were inconclusive. There is, therefore, a growing need to consider new and different treatment strategies, whether they be adjunctive or monotherapeutic, for schizophrenia that continues to be resistant or only partially responsive to treatment.

Adolescent↗

PubMed2005

On the importance of models in interpreting remember-know experiments: comments on Gardiner et al.'s (2002) meta-analysis.

From a meta-analysis of recognition experiments using the remember-know-guess paradigm, Gardiner, Ramponi, and Richardson-Klavehn (2002) reported two findings that they viewed as evidence against the one-dimensional model for that paradigm: (1) Memory strength increased when know responses were added to remember responses, decreasing when guess responses were also included. (2) The accuracy of guess responses was correlated with the location of the old-new criterion in the one-dimensional model for the paradigm, implying that guesses were influenced by decision processes. We question both findings. The first result is contradicted by a signal-detection (SDT) analysis, which shows that both know and guess responses reduced estimated memory strength. The discrepancy results from the properties of A', the measure of accuracy used by Gardiner et al., which we argue is flawed. The second result follows directly from the one-dimensional model, in which accuracy and response criteria are fixed. The authors' reasons for rejecting the one-dimensional model are thus not persuasive, but it can nonetheless be rejected because ROC curves implied by the data are inconsistent with ROCs derived from ratings experiments. A two-dimensional SDT model (Rotello, Macmillan, & Reeder, 2004) accounts for both sets of data. The analysis illustrates the importance of models in interpreting remember--know data.

Bias↗

PubMed1986

16PF research into addiction: meta-analysis and extension.

Meta-analysis of 34 studies on Cattell's 16PF test reveals ragged egos (C-), guilt (O), distrust (L), frustration (Q4), alienation (G-), vague identity (Q3-), alarm (H-), resentment (Q1), quasi-autism (M), scattered intellect (B-), grandiosity (E), autonomy (Q2), infantilism (I), avoidance (A-), and deviousness (N). The aberrant scores on E, G, I, Q1, and Q2 discriminate addicts from suicidals and the chronically ill or unemployed. We found nine types of addicts in our developmental study of 83 members of Alcoholics Anonymous. On the more stable second-order 16PF factors, 43% were highest on Autonomous, 37% on Desperate, 16% on Tough Poise, and 4% on Extravert. Profiles differed more by sexual preference than by gender. Recidivism was highest among homosexual men (38%) and the desperate (25%). Only the Fourth and Fifth Steps of the AA program seem crucial to recovery. Treatment programs based on these and tailored to sexual preference and the second-order personality types seem highly advisable.

Adult↗

PubMed1994

Meta-analysis on long-term clinical performance of posterior composite restorations.

Meta-analysis is a formalized method of combining results of different studies to provide conclusions about the effectiveness of a treatment modality. The aims of this study were to use meta-analysis to determine the clinical performance of posterior composite restorations using the assessment criteria of the USPHS guidelines by combining data from selected multiple studies and to estimate the overall survival rates of posterior composite restorations over time. A computer-aided search of the literature revealed 97 publications on clinical trials of posterior composites in the last 10 years. Following specific selection criteria, which included the year and language of publication, duration of study, class of cavities restored and type of resin composite material used and clinical characteristics assessed; 16 studies were found to be suitable for, and included in a meta-analysis. These involved eight different resin composite materials. Assessment criteria data were extracted from each selected study and tabulated on the basis of years of follow-up and materials. The criteria were coded as binary variables. Homogeneity amongst studies was assessed using Woolf's statistic prior to combining the data. Weighted average proportions and standard errors were determined for each of the assessment criteria. Using Kaplan-Meier estimates, survival analyses of individual assessment criteria (outcomes) for two posterior composite materials were conducted and the resultant survival curves for these outcomes for the two materials are presented. Considering the limited number of studies of variable length available for meta-analysis, the results indicate generally high clinical performance of the various posterior composites for the number of outcomes analysed.

Composite Resins↗

PubMedDate not supplied

[Meta-analysis in urological clinical research].

A systematic review is characterized by the application of the scientific method to the evaluation of scientific literature. When a systematic review uses statistical techniques to combine and summarize the results from previous studies, it is called meta-analysis. Meta-analysis is a working tool that facilitates the realization of systematic and quantitative reviews. Its greater objectivity and rigour in comparison with the traditional reviews make that meta-analysis techniques are little by little being generalized as standard instrument to evaluate scientific evidence. In this article we detail the objectives and applications of this type of studies, as well as the stages in its preparation, including the presentation of results.

Biomedical Research↗

PubMed1997

Cumulating evidence from randomized trials: utilizing sequential monitoring boundaries for cumulative meta-analysis.

We propose the adaptation of classical monitoring boundaries for use in cumulative meta-analysis as guidelines for deciding when accumulating evidence is statistically significant and medically convincing. The interpretation of information from a randomized controlled trial is compared with that from a meta-analysis. The concept of optimal information size for a meta-analysis is developed and used to adapt monitoring boundaries to cumulative meta-analysis.

Fibrinolytic Agents↗

PubMed1999

Meta-analysis of screening data: a survey of the literature.

Meta-analysis has become a popular technique in many areas of biomedical research. While there have been a number of studies and commentaries on the use of meta-analyses and systematic reviews of clinical trials of therapy, little is known about the use of meta-analysis techniques for the evaluation of screening data. This paper presents the first systematic survey of meta-analyses of screening, with an assessment of their methodologic quality and their statistical methods. Our findings show that meta-analysis has not often been used in this area as yet, and that published meta-analyses of screening are often deficient in their reporting of methodology. A brief examination of the evaluative methods of several policy-making groups reveals that they did not routinely use formal quantitative meta-analyses of screening data, at least until 1997. There is considerable potential for meta-analyses of this kind, but improvement in methodological standards will be required to obtain valid conclusions.

Data Interpretation, Statistical↗

PubMed2000

Individual patient data meta-analysis of randomized anti-epileptic drug monotherapy trials.

Meta-analysis may be based on either aggregate data or individual patient data (IPD). Three reasons why IPD are desirable for the meta-analysis of anti-epileptic drug (AED) monotherapy trials are: (1) to undertake a more complete analysis of time-to-event outcomes; (2) to investigate the interaction between AED and type of epilepsy; and (3) to undertake re-analysis of the trial to obtain results for all relevant outcomes. We demonstrate that IPD meta-analysis is possible in AED research. Problems arose from missing data at four levels: (1) unknown trials; (2) known trials but no IPD supplied; (3) known trials but missing outcome data for some individuals within trials; and (4) known trials but missing covariate data for some individuals within trials. Empirical evidence of the reliability of meta-analyses based on aggregate rather than individual patient data is still lacking. Examples of other benefits such projects may bring include improvements to the design of a new trial in the area, in terms of the sample size considerations, the definition of outcomes and data collection.

Anticonvulsants↗

PubMed2002

Meta-analysis of genetic-linkage analysis of quantitative-trait loci.

Meta-analysis is an important tool in linkage analysis. The pooling of results across primary linkage studies allows greater statistical power to detect quantitative-trait loci (QTLs) and more-precise estimation of their genetic effects and, hence, yields conclusions that are stronger relative to those of individual studies. Previous methods for the meta-analysis of linkage studies have been proposed, and, although some methods address the problem of between-study heterogeneity, most methods still require linkage analysis at the same marker or set of markers across studies, whereas others do not result in an estimate of genetic variance. In this study, we present a meta-analytic procedure to evaluate evidence from several studies that report Haseman-Elston statistics for linkage to a QTL at multiple, possibly distinct, markers on a chromosome. This technique accounts for between-study heterogeneity and estimates both the location of the QTL and the magnitude of the genetic effect more precisely than does an individual study. We also provide standard errors for the genetic effect and for the location (in cM) of the QTL, using a resampling method. The approach can be applied under other conditions, provided that the various studies use the same linkage statistic.

Computer Simulation↗