Estimation in meta‐analyses of mean difference and standardized mean difference

Bakbergenuly, Ilyas; Hoaglin, David C.; Kulinskaya, Elena

doi:10.1002/sim.8422

Cited by 42 publications

(57 citation statements)

References 41 publications

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“…55 For meta-analyses of SMDs, measure-specific variance estimators are available. 75 In future studies, it is worthwhile to investigate their performance for the different point and variance estimators of the SMD reviewed in this article.…”

Section: Discussionmentioning

confidence: 99%

Evaluation of various estimators for standardized mean difference in meta‐analysis

Lin

Aloe

2020

Statistics in Medicine

127

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Meta-analyses of a treatment's effect compared with a control frequently calculate the meta-effect from standardized mean differences (SMDs). SMDs are usually estimated by Cohen's d or Hedges' g. Cohen's d divides the difference between sample means of a continuous response by the pooled standard deviation, but is subject to nonnegligible bias for small sample sizes. Hedges' g removes this bias with a correction factor. The current literature (including meta-analysis books and software packages) is confusingly inconsistent about methods for synthesizing SMDs, potentially making reproducibility a problem. Using conventional methods, the variance estimate of SMD is associated with the point estimate of SMD, so Hedges' g is not guaranteed to be unbiased in meta-analyses. This article comprehensively reviews and evaluates available methods for synthesizing SMDs. Their performance is compared using extensive simulation studies and analyses of actual datasets. We find that because of the intrinsic association between point estimates and standard errors, the usual version of Hedges' g can result in more biased meta-estimation than Cohen's d. We recommend using average-adjusted variance estimators to obtain an unbiased meta-estimate, and the Hartung-Knapp-Sidik-Jonkman method for accurate estimation of its confidence interval.

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Section: Discussionmentioning

confidence: 99%

Evaluation of various estimators for standardized mean difference in meta‐analysis

Lin

Aloe

2020

Statistics in Medicine

127

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“…After matching, to assess the balance between the two groups, the standardized mean differences (SMDs) between the TTE cohort and the non-TTE cohort were calculated. SMDs eliminate not only the in uence of the absolute values from a study but also the in uence of the unit of measurement on the results [19]. Continuous variables are shown as the means and standard deviation, and categorical variables are represented as the total and proportion.…”

Section: Methodsmentioning

confidence: 99%

Early Critical Care Transthoracic Echocardiography Improves the Mortality of Patients Undergoing Mechanical Ventilation: Observational Data From Two Large Databases.

Jiang

Chen

et al. 2020

Preprint

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Background: Critical care transthoracic echocardiography (TTE) can quickly and accurately assess haemodynamic changes in ICU patients. However, it is not clear whether transthoracic echocardiography improves the prognosis of mechanically ventilated patients. In this study, we hypothesized that early critical care transthoracic echocardiography independently contributes to improvements in mortality in mechanically ventilated patients in the ICU.Methods: This was a retrospective study based on the Medical Information Mart for Intensive Care III (MIMIC-III) database and the eICU Collaborative Research Database (eICU-CRD). Patients undergoing mechanical ventilation for more than 48 hours were selected. The exposure of interest was early TTE. The primary outcome was in-hospital mortality. We used propensity score matching to analyse the association between early TTE and in-hospital mortality and sensitivity analysis, including the inverse probability weighting model and covariate balancing propensity score model, to ensure the robustness of our findings.Results: A total of 8862 patients undergoing mechanical ventilation were enrolled. The adjusted OR showed a favourable effect between the early TTE group and in-hospital mortality [MIMIC: OR 0.77, 95% CI (0.63–0.94), (P=0.01); eICU-CRD: OR 0.78, 95% CI (0.68–0.89), (P<0.01) ]. Furthermore, TTE was also associated with 30-day mortality in the MIMIC database [OR 0.74, 95% CI (0.6-0.92), P=0.01].Conclusions: Early application of critical care transthoracic echocardiography during mechanical ventilation is beneficial for improving in-hospital mortality. Further investigation with prospectively collected data is required to validate this relationship.

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“…When analyzing the difference of continuous data, the mean difference (MD) with 95% con dence interval (CI) is used as the effect size [23]; when analyzing the difference of the binary data, the relative risk (RR) with 95% CI is used as the effect size. Heterogeneity was examined using the I 2 statistic that indicates the proportion of total variability in estimates that can be attributed to heterogeneity [24].…”

Section: Introductionmentioning

confidence: 99%

Early Tracheal Extubation for Postoperative Recovery in Cardiac Surgery: Systematic Review and Meta-Analysis

Zhao

Huang

Chao

et al. 2020

Preprint

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Background: How to promote the rapid recovery of patients undergoing cardiac surgery and quality of life has been the focus of doctors’ attention. To compare the safety and efficacy of early cardiac extubation with conventional extubation (late extubation) in patients undergoing cardiac surgery.Methods: Ovid MEDLINE, Ovid Embase, EBSCOhost, Cochrane Library and ISIWeb of Science (1946–November 25, 2019) were searched to obtain randomized controlled trials of early tracheal extubation in patients undergoing cardiac surgery.Results: Compared with the conventional care group, in terms of effectiveness, the intensive care unit (ICU) stay and hospital length of stay in the early tracheal extubation was significantly shorter. In terms of security, most outcomes, including mortality, bleeding, stroke, acute renal failure and arrhythmia, were not statistically significant, except for myocardial infarction. However, the risk of re-intubation in the early tracheal extubation was higher than that of conventional extubation.Conclusions: This meta-analysis confirmed that early tracheal extubation may effectively reduce ICU hospitalization time, hospital length of stay and the risk of myocardial infarction. Although early tracheal extubation does not increase the risk of safety events, the clinicians need to pay more attention to be aware of possible risk of re-intubation. Meanwhile, as a key time point for extubation within 4 hours, it may help a little to reduce the risk of re-intubation and myocardial infarction.

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Estimation in meta‐analyses of mean difference and standardized mean difference

Cited by 42 publications

References 41 publications

Evaluation of various estimators for standardized mean difference in meta‐analysis

Evaluation of various estimators for standardized mean difference in meta‐analysis

Early Critical Care Transthoracic Echocardiography Improves the Mortality of Patients Undergoing Mechanical Ventilation: Observational Data From Two Large Databases.

Early Tracheal Extubation for Postoperative Recovery in Cardiac Surgery: Systematic Review and Meta-Analysis

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