In an empirical evaluation of the funnel plot, researchers could not visually identify publication bias

Inadequate use and regulation of interventions against publication bias decreases their effectiveness: a systematic review

Objectives

To determine the effectiveness of interventions designed to prevent or reduce publication and related biases.

Study Design and Setting

We searched multiple databases and performed manual searches using terms related to publication bias and known interventions against publication bias. We dually reviewed citations and assessed risk of bias. We synthesized results by intervention and outcomes measured and graded the quality of the evidence (QoE).

Results

We located 38 eligible studies. The use of prospective trial registries (PTR) has increased since 2005 (seven studies, moderate QoE); however, positive outcome-reporting bias is prevalent (14 studies, low QoE), and information in nonmandatory fields is vague (10 studies, low QoE). Disclosure of financial conflict of interest (CoI) is inadequate (five studies, low QoE). Blinding peer reviewers may reduce geographical bias (two studies, very low QoE), and open-access publishing does not discriminate against authors from low-income countries (two studies, very low QoE).

Conclusion

The use of PTR and CoI disclosures is increasing; however, the adequacy of their use requires improvement. The effect of open-access publication and blinding of peer reviewers on publication bias is unclear, as is the effect of other interventions such as electronic publication and authors' rights to publish their results.

Colder-to-warmer changes in children's blood lead concentrations are related to previous blood lead status: results from a systematic review of prospective studies

OBJECTIVE

To estimate the extent of changes in mean BLLs from colder to warmer months, in children aged 1-5 years with different status of lead in colder months.

METHODOLOGY

We performed a systematic review using an in-house algorithm developed in MEDLINE, EMBASE, Web of Science, and CINHAL. Search was performed between November 2012 and July 2013, and data evaluation and extraction were subsequently conducted. The mean BLLs observed in the warmer months was divided by the one observed in the colder months to obtain the warmer-to-colder ratio (WCR). Study-specific WCRs were pooled using the fixed-effects method of Mantel-Haenszel to estimate the combined WCR.

RESULTS

From 4040 papers initially identified, eight cohort studies were considered relevant for inclusion. The combined WCR was inversely related to the BLLs observed during colder months. The values were 1.25 (95% CI: 0.90-1.60), 1.06 (95% CI: 0.92-1.19), and 0.95 (95% CI: 0.51-1.39) for children showing baseline BLLs of <10μgdL(-1), 10-20μgdL(-1)and ≥20μgdL(-1), respectively. The combined WCR was influenced neither by children's age nor place/date of study.

CONCLUSION

The extent of the summer increase in BLLs depends on the BLLs in the colder months.

The effects of psychological interventions on depression and anxiety among Chinese adults with cancer: a meta-analysis of randomized controlled studies

Background

Our previous studies found the high prevalence of depression and anxiety among Chinese cancer patients, and many empirical studies have been conducted to evaluate the effects of psychological interventions on depression and anxiety among Chinese cancer patients. This study aimed to conduct a meta-analysis in order to assess the effects of psychological interventions on depression and anxiety in Chinese adults with cancer.

Methods

The four most comprehensive Chinese academic database- CNKI, Wanfang, Vip and CBM databases-were searched from their inception until January 2014. PubMed and Web of Science (SCIE) were also searched from their inception until January 2014 without language restrictions, and an internet search was used. Randomized controlled studies assessing the effects of psychological interventions on depression and anxiety among Chinese adults with cancer were analyzed. Study selection and appraisal were conducted independently by three authors. The pooled random-effects estimates of standardized mean difference (SMD) and 95% confidence intervals (CI) were calculated. Moderator analysis (meta-regression and subgroup analysis) was used to explore reasons for heterogeneity.

Results

We retrieved 147 studies (covering 14,039 patients) that reported 253 experimental-control comparisons. The random effects model showed a significant large effect size for depression (SMD = 1.199, p < 0.001; 95% CI = 1.095-1.303) and anxiety (SMD = 1.298, p < 0.001; 95% CI = 1.187-1.408). Cumulative meta-analysis indicated that sufficient evidence had accumulated since 2000–2001 to confirm the statistically significant effectiveness of psychological interventions on depression and anxiety in Chinese cancer patients. Moderating effects were found for caner type, patients’ selection, intervention format and questionnaires used. In studies that included lung cancer, preselected patients with clear signs of depression/anxiety, adopted individual intervention and used State-Trait Anxiety Inventory (STAI), the effect sizes were larger.

Conclusions

We concluded that psychological interventions in Chinese cancer patients have large effects on depression and anxiety. The findings support that an adequate system should be set up to provide routine psychological interventions for cancer patients in Chinese medical settings. However, because of some clear limitations (heterogeneity and publication bias), these results should be interpreted with caution.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2407-14-956) contains supplementary material, which is available to authorized users.

Pharmacological and nonpharmacological prevention of fentanyl-induced cough: a meta-analysis

Fentanyl-induced cough (FIC) is often observed after intravenous bolus administration of fentanyl during anesthesia induction. This meta-analysis assessed the efficacy of pharmacological and nonpharmacological interventions to reduce the incidence of FIC. We searched for randomized controlled trials comparing pharmacological or nonpharmacological interventions with controls to prevent FIC; we included 28 studies retrieved from Pub-Med, Embase, and Cochrane Library. Overall incidence of FIC was approximately 31 %. Lidocaine [odds ratio (OR) = 0.29, 95 % confidence interval (CI) 0.21–0.39], N-methyl-D-aspartate (NMDA) receptor antagonists (OR 0.09, 95 % CI 0.02–0.42), propofol (OR 0.07, 95 % CI 0.01–0.36), a2 agonists (OR 0.32, 95 % CI 0.21–0.48), b2 agonists (OR 0.10, 95 % CI 0.03–0.30), fentanyl priming (OR 0.33, 95 % CI 0.19–0.56), and slow injection of fentanyl (OR 0.25, 95 % CI 0.11–0.58)] were effective in decreasing the incidence of FIC, whereas atropine (OR 1.10, 95 % CI 0.58–2.11) and benzodiazepines (OR 2.04, 95 % CI 1.33–3.13) were not effective. This meta-analysis found that lidocaine, NMDA receptor antagonists, propofol, a2 agonists, b2 agonists, and priming dose of fentanyl were effective in preventing FIC, but atropine and benzodiazepines were not. Slow injection of fentanyl was effective in preventing FIC, but results depend on the speed of administration.

Introduction to the GRADE approach for guideline development: considerations for physical therapist practice

BACKGROUND

Practice guidelines (guidelines) have an increasing role in health care delivery and are being published more frequently. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) is an approach for guideline development. The GRADE approach has been adopted by multiple national and international organizations producing guidelines related to physical therapist care.

OBJECTIVE

The purpose of this article is to introduce physical therapists to the GRADE approach for guideline development.

RESULTS

GRADE provides a consistent approach for guideline development and transparency in the communication of how the guidelines were developed and how the recommendations were reached, leading to informed choices by patients, clinicians, and policy makers in health care. GRADE leads to a clear distinction between the strength of the evidence and the recommendation. Both the direction (for or against) and the strength (weak or strong) of the recommendation are considered. For determining the strength of the recommendation, GRADE takes into account the quality of evidence, the balance of benefit and harm, uncertainty about or variability in patients' values and preferences, and uncertainty about whether the intervention is a wise use of resources.

LIMITATIONS

The GRADE approach has been used primarily with interventions and clinical questions and less often with questions related to diagnosis and prognosis.

CONCLUSIONS

The frequency of publication of guidelines is increasing. To make informed choices in the health care system, physical therapists should understand how guidelines are developed. The GRADE approach has been adopted by national and international organizations that produce guidelines relevant to physical therapist practice. Understanding the GRADE approach will enable physical therapists to make informed clinical choices.

Publication bias & small-study effects in pediatric dentistry meta-analyses

OBJECTIVES

The aim of this study was to examine the presence and extent of publication bias and small-study effects in meta-analyses (MAs) investigating pediatric dentistry-related subjects.

METHODS

Following a literature search, 46 MAs including 882 studies were analyzed qualitatively. Of these, 39 provided enough data to be re-analyzed. Publication bias was assessed with the following methods: contour-enhanced funnel plots, Begg and Mazumdar's rank correlation and Egger's linear regression tests, Rosenthal's failsafe N, and Duval and Tweedie's "trim and fill" procedure.

RESULTS

Only a few MAs adequately assessed the existence and effect of publication bias. Inspection of the funnel plots indicated asymmetry, which was confirmed by Begg-Mazumdar's test in 18% and by Egger's test in 33% of the MAs. According to Rosenthal's criterion, 80% of the MAs were robust, while adjusted effects with unpublished studies differed from little to great from the unadjusted ones. Pooling of the Egger's intercepts indicated that evidence of asymmetry was found in the pediatric dental literature, which was accentuated in dental journals and in diagnostic MAs. Since indications of small-study effects and publication bias in pediatric dentistry were found, the influence of small or missing trials on estimated treatment effects should be routinely assessed in future MAs.

Clinical trials registries are under-utilized in the conduct of systematic reviews: a cross-sectional analysis

BACKGROUND

Publication bias is a major threat to the validity of systematic reviews. Searches of clinical trials registries can help to identify unpublished trials, though little is known about how often these resources are utilized. We assessed the usage and results of registry searches reported in systematic reviews published in major general medical journals.

METHODS

This cross-sectional analysis includes data from systematic reviews assessing medical interventions which were published in one of six major general medical journals between July 2012 and June 2013. Two authors independently examined each published systematic review and all available supplementary materials to determine whether at least one clinical trials registry was searched.

RESULTS

Of the 117 included systematic reviews, 41 (35%) reported searching a trials registry. Of the 29 reviews which also provided detailed registry search results, 15 (52%) identified at least one completed trial and 18 (62%) identified at least one ongoing trial.

CONCLUSIONS

Clinical trials registry searches are not routinely included in systematic reviews published in major medical journals. Routine examination of registry databases may allow a more accurate characterization of publication and outcome reporting biases and improve the validity of estimated effects of medical treatments.

Systematic Reviews Published in Emergency Medicine Journals Do Not Routinely Search Clinical Trials Registries: A Cross-Sectional Analysis

STUDY OBJECTIVE

Publication bias compromises the validity of systematic reviews. This problem can be addressed in part through searching clinical trials registries to identify unpublished studies. This study aims to determine how often systematic reviews published in emergency medicine journals include clinical trials registry searches.

METHODS

We identified all systematic reviews published in the 6 highest-impact emergency medicine journals between January 1 and December 31, 2013. Systematic reviews that assessed the effects of an intervention were further examined to determine whether the authors described searching a clinical trials registry and whether this search identified relevant unpublished studies.

RESULTS

Of 191 articles identified through PubMed search, 80 were confirmed to be systematic reviews. Our sample consisted of 41 systematic reviews that assessed a specific intervention. Eight of these 41 (20%) searched a clinical trials registry. For 4 of these 8 reviews, the registry search identified at least 1 relevant unpublished study.

CONCLUSION

Systematic reviews published in emergency medicine journals do not routinely include searches of clinical trials registries. By helping authors identify unpublished trial data, the addition of registry searches may improve the validity of systematic reviews.

Systematic review of trial-based analyses reporting the economic impact of heart failure management programs compared with usual care

BACKGROUND

The cost-effectiveness of heart failure management programs (HF-MPs) is highly variable. We explored intervention and clinical characteristics likely to influence cost outcomes.

METHODS

A systematic review of economic analyses alongside randomized clinical trials comparing HF-MPs and usual care. Electronic databases were searched for English peer-reviewed articles published between 1990 and 2013.

RESULTS

Of 511 articles identified, 34 comprising 35 analyses met the inclusion criteria. Eighteen analyses (51%) reported a HF-MP as more effective and less costly; four analyses (11%), and five analyses (14%) also reported they were more effective but with no significant or an increased cost difference, respectively. Alternatively, five analyses (14%) reported no statistically significant difference in effects or costs, and one analysis (3%) reported no statistically significant effect difference but was less costly. Finally, two analyses (6%) reported no statistically significant effect difference but were more costly. Interventions that reduced hospital admissions tended to result in favorable cost outcomes, moderated by increased resource use, intervention cost and/or the durability of the intervention effect. The reporting quality of economic evaluation assessed by the Consolidated Health Economic Evaluation Reporting Standards (CHEERS) checklist varied substantially between 5% and 91% (median 45%; 34 articles) of the checklist criteria adequately addressed. Overall, none of the study, patient or intervention characteristics appeared to independently influence the cost-effectiveness of a HF-MP.

CONCLUSION

The extent that HF-MPs reduce hospital readmissions appears to be associated with favorable cost outcomes. The current evidence does not provide a sufficient evidence base to explain what intervention or clinical attributes may influence the cost implications.

Pharmacological interventions for improved colonic anastomotic healing: A meta-analysis

AIM: To identify pharmaceuticals for the prophylaxis of anastomotic leakage (AL), we systematically reviewed studies on anastomosis repair after colorectal surgery.

METHODS: We searched PubMed and EMBASE for articles published between January 1975 and December 2012. We included studies in English with the primary purpose of promoting healing of anastomoses made in the colon or rectum under uncomplicated conditions. We excluded studies on adverse events from interventions, nutritional interventions or in situ physical supporting biomaterials. The primary outcome was biomechanical strength or AL. We performed meta-analyses on therapeutic agents investigated by three or more independent research groups using the same outcome. The DerSimonian-Laird method for random effects was applied with P < 0.05.

RESULTS: Of the 56 different therapeutic agents assessed, 7 met our inclusion criteria for the meta-analysis. The prostacyclin analog iloprost increased the weighted mean of the early bursting pressure of colonic anastomoses in male rats by 60 mmHg (95%CI: 30-89) vs the controls, and the immunosuppressant tacrolimus increased this value by 29 mmHg (95%CI: 4-53) vs the controls. Erythropoietin showed an enhancement of bursting pressure by 45 mmHg (95%CI: 14-76). The anabolic compound growth hormone augmented the anastomotic strength by 21 mmHg (95%CI: 7-35), possibly via the up-regulation of insulin-like growth factor-1, as this growth factor increased the bursting pressure by 61 mmHg (95%CI: 43-79) via increased collagen deposition. Hyperbaric oxygen therapy increased the bursting pressure by 24 mmHg (95%CI: 13-34). Broad-spectrum matrix metalloproteinase inhibitors increased the bursting pressure by 48 mmHg (95%CI: 31-66) on postoperative days 3-4. In the only human study, the AL incidence was not significantly reduced in the 103 colorectal patients treated with aprotinin (11.7%) compared with the 113 placebo-treated patients (9.7%).

CONCLUSION: This systematic review identified only one randomized clinical trial and seven therapeutic agents from pre-clinical models that could be explored further for the prophylaxis of AL after colorectal surgery.

The pros and cons of funnel plots as an aid to risk communication and patient decision making

Funnel plots, which simultaneously display a sample statistic and the corresponding sample size for multiple cases, have a range of applications. In medicine, they are used to display treatment outcome rates and caseload volume by institution, which can inform strategic decisions about health care delivery. We investigated lay people's understanding of such plots and explored their suitability as an aid to individual treatment decisions. In two studies, 172 participants answered objective questions about funnel plots representing the surgical outcomes (survival or mortality rates) of institutions varying in caseload, and indicated their preferred institutions. Accuracy for extracting objective information was high, unless question phrasing was inconsistent with the plot's survival/mortality framing, or participants had low numeracy levels. Participants integrated caseload-volume and outcome-rate data when forming preferences, but were influenced by reference lines on the plot to make inappropriate discriminations between institutions with similar outcome rates. With careful choice of accompanying language, funnel plots can be readily understood and are therefore a useful tool for communicating risk. However, they are less effective as a decision aid for individual patient's treatment decisions, and we recommend refinements to the standard presentation of the plots if they are to be used for that purpose.

Laser acupuncture for treating musculoskeletal pain: a systematic review with meta-analysis

Laser acupuncture has been studied extensively over several decades to establish evidence-based clinical practice. This systematic review aims to evaluate the effects of laser acupuncture on pain and functional outcomes when it is used to treat musculoskeletal disorders and to update existing evidence with data from recent randomized controlled trials (RCTs). A computer-based literature search of the databases MEDLINE, AMED, EMBASE, CINAHL, SPORTSDiscus, Cochrane Library, PubMed, Current Contents Connect, Web of Science, and SCOPUS was used to identify RCTs comparing between laser acupuncture and control interventions. A meta-analysis was performed by calculating the standardized mean differences and 95% confidence intervals, to evaluate the effect of laser acupuncture on pain and functional outcomes. Included studies were assessed in terms of their methodological quality and appropriateness of laser parameters. Forty-nine RCTs met the inclusion criteria. Two-thirds (31/49) of these studies reported positive effects, were of high methodological quality, and reported the dosage adequately. Negative or inconclusive studies commonly failed to demonstrate these features. For all diagnostic subgroups, positive effects for both pain and functional outcomes were more consistently seen at long-term follow-up rather than immediately after treatment. Moderate-quality evidence supports the effectiveness of laser acupuncture in managing musculoskeletal pain when applied in an appropriate treatment dosage; however, the positive effects are seen only at long-term follow-up and not immediately after the cessation of treatment.

Frontal midline theta reflects anxiety and cognitive control: meta-analytic evidence

Evidence from imaging and anatomical studies suggests that the midcingulate cortex (MCC) is a dynamic hub lying at the interface of affect and cognition. In particular, this neural system appears to integrate information about conflict and punishment in order to optimize behavior in the face of action-outcome uncertainty. In a series of meta-analyses, we show how recent human electrophysiological research provides compelling evidence that frontal-midline theta signals reflecting MCC activity are moderated by anxiety and predict adaptive behavioral adjustments. These findings underscore the importance of frontal theta activity to a broad spectrum of control operations. We argue that frontal-midline theta provides a neurophysiologically plausible mechanism for optimally adjusting behavior to uncertainty, a hallmark of situations that elicit anxiety and demand cognitive control. These observations compel a new perspective on the mechanisms guiding motivated learning and behavior and provide a framework for understanding the role of the MCC in temperament and psychopathology.

Testing for publication bias in diagnostic meta-analysis: a simulation study

The present study investigates the performance of several statistical tests to detect publication bias in diagnostic meta-analysis by means of simulation. While bivariate models should be used to pool data from primary studies in diagnostic meta-analysis, univariate measures of diagnostic accuracy are preferable for the purpose of detecting publication bias. In contrast to earlier research, which focused solely on the diagnostic odds ratio or its logarithm ( ln ω), the tests are combined with four different univariate measures of diagnostic accuracy. For each combination of test and univariate measure, both type I error rate and statistical power are examined under diverse conditions. The results indicate that tests based on linear regression or rank correlation cannot be recommended in diagnostic meta-analysis, because type I error rates are either inflated or power is too low, irrespective of the applied univariate measure. In contrast, the combination of trim and fill and ln ω has non-inflated or only slightly inflated type I error rates and medium to high power, even under extreme circumstances (at least when the number of studies per meta-analysis is large enough). Therefore, we recommend the application of trim and fill combined with ln ω to detect funnel plot asymmetry in diagnostic meta-analysis.

Chinese patent medicine tongxinluo capsule for hypertension: a systematic review of randomised controlled trials

This study was intended to evaluate the efficacy and safety of Tongxinluo capsule for hypertension. Search Strategy. We searched the Cochrane Central Register of Controlled Trials (CENTRAL) in the Cochrane Library, The PubMed, EMBASE, Chinese Bio-Medical Literature Database (CBM), Chinese National Knowledge Infrastructure (CNKI), Chinese Scientific Journal Database, and Wan-fang Data started from the first of database to October 28, 2013. No language restriction was applied. We included randomized clinical trials testing Tongxinluo capsule against western medicine, Tongxinluo capsule versus placebo, and Tongxinluo capsule combined with western medicine versus western medicine. Study selection, data extraction, quality assessment, and data analyses were conducted according to the Cochrane standards. Results. 25 trials with 1958 participants were included. The methodological quality of the included trials was evaluated as generally low. The blood pressure (BP) lowering effect of Tongxinluo capsule plus western medicine was significantly higher than that of western medicine (systolic blood pressure (SBP): -3.87, -5.32 to -2.41, P < 0.00001; and diastolic blood pressure (DBP): -2.72, -4.19 to -1.24, P = 0.0003). The BP also decreased significantly from baseline with Tongxinluo capsule than placebo (SBP: -9.40, -10.90 to -7.90, P < 0.00001; and DBP: -11.80, -12.40 to -11.20, P < 0.00001) or western medicine (SBP: -3.90, -4.93 to -2.87, P < 0.00001; and DBP: -3.70, -3.83 to -3.57, P < 0.00001). 12 trials reported adverse events without details. Conclusions. There is some but weak evidence about the effectiveness of TXL in treating patients with hypertension.

Assessing small study effects and publication bias in orthodontic meta-analyses: a meta-epidemiological study

OBJECTIVE

The aim of this study was to examine the presence and extent of small study effects and publication bias in meta-analyses (MAs) based on orthodontic studies.

MATERIALS AND METHODS

Following an extensive literature search, 25 MAs including 313 studies were identified and were possible to be re-analyzed. For the assessment of publication bias, contour-enhanced funnel plots were examined and their symmetry was tested using the Begg and Mazumdar rank correlation and Egger's linear regression tests. Robustness of MAs' results to publication bias was examined by Rosenthal's failsafe N, and adjusted effect sizes were calculated after consideration of publication bias using Duval and Tweedie's "trim and fill" procedure.

RESULTS

Only few of the originally published MAs assessed the existence and effect of publication bias and some only partially. Inspection of the funnel plots indicated possible asymmetry, which was confirmed by Begg and Mazumdar's test in 12 % and by Egger's test in 28 % of the MAs. According to Rosenthal's criterion, 62 % of the MAs were robust, while adjusted effect estimates with unpublished studies differed from little to great from the unadjusted ones. Pooling of Egger's intercepts of included MAs indicated that evidence of asymmetry was found in the orthodontic literature, which was accentuated in medical journals and in diagnostic MAs.

CONCLUSIONS

Small study effects and publication bias can often distort results of MAs. Since indications of publication bias in orthodontics were found, the influence of small trials on estimated treatment effects should be routinely and more carefully assessed by authors conducting MAs.

Effects of genotypic and phenotypic variation on establishment are important for conservation, invasion, and infection biology

There is abundant evidence that the probability of successful establishment in novel environments increases with number of individuals in founder groups and with number of repeated introductions. Theory posits that the genotypic and phenotypic variation among individuals should also be important, but few studies have examined whether founder diversity influences establishment independent of propagule pressure, nor whether the effect is model or context dependent. I summarize the results of 18 experimental studies and report on a metaanalysis that provides strong evidence that higher levels of genotypic and phenotypic diversity in founder groups increase establishment success in plants and animals. The effect of diversity is stronger in experiments carried out under natural conditions in the wild than under seminatural or standardized laboratory conditions. The realization that genetic and phenotypic variation is key to successful establishment may improve the outcome of reintroduction and translocation programs used to vitalize or restore declining and extinct populations. Founder diversity may also improve the ability of invasive species to establish and subsequently spread in environments outside of their native community, and enhance the ability of pathogens and parasites to colonize and invade the environment constituted by their hosts. It is argued that exchange of ideas, methodological approaches, and insights of the role of diversity for establishment in different contexts may further our knowledge, vitalize future research, and improve management plans in different disciplines.

Selective laser trabeculoplasty versus argon laser trabeculoplasty in patients with open-angle glaucoma: a systematic review and meta-analysis

Objective

To examine possible differences in clinical outcomes between selective laser trabeculoplasty (SLT) and argon laser trabeculoplasty (ALT) in open-angle glaucoma at different times post-treatment.

Methods

Randomized controlled trials (RCTs) comparing SLT versus ALT were searched through August 2013. The main outcome measure was IOP, and secondary outcomes included the number of glaucoma medications, the success rate, and adverse events.

Results

Six RCTs, involving 482 eyes treated with laser trabeculoplasty, were included in the meta-analysis. For all patients (including first and previous laser trabeculoplasy), no significant difference in IOP lowering was observed between SLT and ALT at one hour (P = 0.40), one week (P = 0.72), one month (P = 0.37), six months (P = 0.08), one year (P = 0.34), two years (P = 0.58), three years (P = 0.34), four years (P = 0.47), and five years (P = 0.50). A statistically significant difference in favor of SLT was found when comparing the IOP reduction at three months after intervention (weighted mean difference (WMD): 1.19 mmHg [0.41; 1.97]; I²=0%; P = 0.003). For patients who were naive to laser, there was no significant difference of reduction in IOP comparing SLT with ALT at any time point. In patients’ previous LT, no statistically significant difference in IOP reduction was found at six months (WMD: 1.92 mmHg [-0.91; 4.74]; I² = 77.3%; P = 0.18). There was no significant difference in the reduction in the number of glaucoma medications, the success rate, or adverse event rates between the two treatments.

Conclusions

SLT has equivalent efficacy to ALT with a similar constellation of side effects. In the case of retreatment, SLT appears to be similar to ALT in IOP lowering at six months.

Is fat talking a causal risk factor for body dissatisfaction? A systematic review and meta-analysis

OBJECTIVE

Fat talking has been assumed to be a causal risk factor for body dissatisfaction in a number of prevention programs and body confidence campaigns. The aim of this paper was to assess whether fat talking meets three criteria necessary for causal risk factors, namely whether fat talking is: (a) cross-sectionally associated with body dissatisfaction; (b) prospectively associated with changes in body dissatisfaction; and (c) associated with changes in body dissatisfaction in experimental studies.

METHOD

A systematic literature review was conducted using electronic databases and hand searching of relevant journals. Meta-analyses provided pooled effect size estimates, and meta-regressions were used to determine whether age, gender or risk of bias were effect modifiers of the relationship.

RESULTS

Searches revealed 24 studies. There was a significant cross-sectional association (r = 0.297, 95% CI = 0.225-0.349), which differed in strength between age groups and genders. There was a prospective association between fat talking and changes in body dissatisfaction in long term (r = 0.144, 95% CI = 0.050-0.234), but not in short-term studies (r = 0.022, 95% CI = -0.131-0.174). One study showed that experimental exposure to fat talking was associated with increases in body dissatisfaction (d = 0.124).

DISCUSSION

As such, there is good evidence that fat talking is a correlate of body dissatisfaction. The few prospective and experimental studies give an initial indication that fat talking is a causal risk factor for body dissatisfaction. Further work is needed to support this position.

Airways in out-of-hospital cardiac arrest: systematic review and meta-analysis

OBJECTIVE

To determine the differences in survival for out-of-hospital advanced airway intervention (AAI) compared with basic airway intervention (BAI) in cardiac arrest.

BACKGROUND

AAI is commonly utilized in cardiac arrest in the out-of-hospital setting as a means to secure the airway. Observational studies and clinical trials of AAI suggest that AAI is associated with worse outcomes in terms of survival. No controlled trials exist that compares AAI to BAI.

METHODS

We conducted a bias-adjusted meta-analysis on 17 observational studies. The outcomes were survival, short-term (return of spontaneous circulation and to hospital admission), and longer-term (to discharge, to one month survival). We undertook sensitivity analyses by analyzing patients separately: those who were 16 years and older, nontrauma only, and attempted versus successful AAI.

RESULTS

This meta-analysis included 388,878 patients. The short-term survival for AAI compared to BAI were overall OR 0.84(95% CI 0.62 to 1.13), for endotracheal intubation (ETI) OR 0.79 (95% CI 0.54 to 1.16), and for supraglottic airways (SGA) OR 0.59 (95% CI 0.39 to 0.89). Long-term survival for AAI were overall OR 0.49 (95% CI 0.37 to 0.65), for ETI OR 0.48 (95% CI 0.36 to 0.64), and for SGA OR 0.35 (95% CI 0.28 to 0.44). Sensitivity analyses shows that limiting analyses to adults, non-trauma victims, and instances where AAI was both attempted and successful did not alter results meaningfully. A third of all studies did not adjust for any other confounding factors that could impact on survival.

CONCLUSIONS

This meta-analysis shows decreased survival for AAIs used out-of-hospital in cardiac arrest, but are likely biased due to confounding, especially confounding by indication. A properly conducted prospective study or a controlled trial is urgently needed and are possible to do.

Detecting, quantifying and adjusting for publication bias in meta-analyses: protocol of a systematic review on methods

BACKGROUND

Health professionals and policymakers aspire to make healthcare decisions based on the entire relevant research evidence. This, however, can rarely be achieved because a considerable amount of research findings are not published, especially in case of 'negative' results - a phenomenon widely recognized as publication bias. Different methods of detecting, quantifying and adjusting for publication bias in meta-analyses have been described in the literature, such as graphical approaches and formal statistical tests to detect publication bias, and statistical approaches to modify effect sizes to adjust a pooled estimate when the presence of publication bias is suspected. An up-to-date systematic review of the existing methods is lacking.

METHODS/DESIGN

The objectives of this systematic review are as follows:• To systematically review methodological articles which focus on non-publication of studies and to describe methods of detecting and/or quantifying and/or adjusting for publication bias in meta-analyses.• To appraise strengths and weaknesses of methods, the resources they require, and the conditions under which the method could be used, based on findings of included studies.We will systematically search Web of Science, Medline, and the Cochrane Library for methodological articles that describe at least one method of detecting and/or quantifying and/or adjusting for publication bias in meta-analyses. A dedicated data extraction form is developed and pilot-tested. Working in teams of two, we will independently extract relevant information from each eligible article. As this will be a qualitative systematic review, data reporting will involve a descriptive summary.

DISCUSSION

Results are expected to be publicly available in mid 2013. This systematic review together with the results of other systematic reviews of the OPEN project (To Overcome Failure to Publish Negative Findings) will serve as a basis for the development of future policies and guidelines regarding the assessment and handling of publication bias in meta-analyses.

Systematic reviews and meta-analyses of home telemonitoring interventions for patients with chronic diseases: a critical assessment of their methodological quality

BACKGROUND

Systematic reviews and meta-analyses of home telemonitoring interventions for patients with chronic diseases have increased over the past decade and become increasingly important to a wide range of clinicians, policy makers, and other health care stakeholders. While a few criticisms about their methodological rigor and synthesis approaches have recently appeared, no formal appraisal of their quality has been conducted yet.

OBJECTIVE

The primary aim of this critical review was to evaluate the methodology, quality, and reporting characteristics of prior reviews that have investigated the effects of home telemonitoring interventions in the context of chronic diseases.

METHODS

Ovid MEDLINE, the Database of Abstract of Reviews of Effects (DARE), and Health Technology Assessment Database (HTA) of the Cochrane Library were electronically searched to find relevant systematic reviews, published between January 1966 and December 2012. Potential reviews were screened and assessed for inclusion independently by three reviewers. Data pertaining to the methods used were extracted from each included review and examined for accuracy by two reviewers. A validated quality assessment instrument, R-AMSTAR, was used as a framework to guide the assessment process.

RESULTS

Twenty-four reviews, nine of which were meta-analyses, were identified from more than 200 citations. The bibliographic search revealed that the number of published reviews has increased substantially over the years in this area and although most reviews focus on studying the effects of home telemonitoring on patients with congestive heart failure, researcher interest has extended to other chronic diseases as well, such as diabetes, hypertension, chronic obstructive pulmonary disease, and asthma. Nevertheless, an important number of these reviews appear to lack optimal scientific rigor due to intrinsic methodological issues. Also, the overall quality of reviews does not appear to have improved over time. While several criteria were met satisfactorily by either all or nearly all reviews, such as the establishment of an a priori design with inclusion and exclusion criteria, use of electronic searches on multiple databases, and reporting of studies characteristics, there were other important areas that needed improvement. Duplicate data extraction, manual searches of highly relevant journals, inclusion of gray and non-English literature, assessment of the methodological quality of included studies and quality of evidence were key methodological procedures that were performed infrequently. Furthermore, certain methodological limitations identified in the synthesis of study results have affected the results and conclusions of some reviews.

CONCLUSIONS

Despite the availability of methodological guidelines that can be utilized to guide the proper conduct of systematic reviews and meta-analyses and eliminate potential risks of bias, this knowledge has not yet been fully integrated in the area of home telemonitoring. Further efforts should be made to improve the design, conduct, reporting, and publication of systematic reviews and meta-analyses in this area.

Anti-methanogenic effects of monensin in dairy and beef cattle: a meta-analysis

Monensin is a widely used feed additive with the potential to minimize methane (CH4) emissions from cattle. Several studies have investigated the effects of monensin on CH4, but findings have been inconsistent. The objective of the present study was to conduct meta-analyses to quantitatively summarize the effect of monensin on CH4 production (g/d) and the percentage of dietary gross energy lost as CH4 (Ym) in dairy cows and beef steers. Data from 22 controlled studies were used. Heterogeneity of the monensin effects were estimated using random effect models. Due to significant heterogeneity (>68%) in both dairy and beef studies, the random effect models were then extended to mixed effect models by including fixed effects of DMI, dietary nutrient contents, monensin dose, and length of monensin treatment period. Monensin reduced Ym from 5.97 to 5.43% and diets with greater neutral detergent fiber contents (g/kg of dry matter) tended to enhance the monensin effect on CH4 in beef steers. When adjusted for the neutral detergent fiber effect, monensin supplementation [average 32 mg/kg of dry matter intake (DMI)] reduced CH4 emissions from beef steers by 19±4 g/d. Dietary ether extract content and DMI had a positive and a negative effect on monensin in dairy cows, respectively. When adjusted for these 2 effects in the final mixed-effect model, monensin feeding (average 21 mg/kg of DMI) was associated with a 6±3 g/d reduction in CH4 emissions in dairy cows. When analyzed across dairy and beef cattle studies, DMI or monensin dose (mg/kg of DMI) tended to decrease or increase the effect of monensin in reducing methane emissions, respectively. Methane mitigation effects of monensin in dairy cows (-12±6 g/d) and beef steers (-14±6 g/d) became similar when adjusted for the monensin dose differences between dairy cow and beef steer studies. When adjusted for DMI differences, monensin reduced Ym in dairy cows (-0.23±0.14) and beef steers (-0.33±0.16). Monensin treatment period length did not significantly modify the monensin effects in dairy cow or beef steer studies. Overall, monensin had stronger antimethanogenic effects in beef steers than dairy cows, but the effects in dairy cows could potentially be improved by dietary composition modifications and increasing the monensin dose.

A Primer on Performing Systematic Reviews and Meta-analyses

The number of systematic reviews published in the peer-reviewed literature has increased dramatically in the last decade, and for good reason. They have become an essential resource for clinicians who want unbiased and current answers for their clinical questions; researchers and funders who want to identify the most critical evidence gaps for study; payers and administrators who want to make coverage, formulary, and purchasing decisions; and policymakers who want to develop quality measures and clinical guidelines. Targeted to beginners interested in conducting their own systematic reviews and users of systematic reviews looking for a brief introduction, this primer (1) highlights the differences between review types; (2) outlines the major steps in performing a systematic review; and (3) offers a set of resources to help authors perform and report valid and actionable systematic reviews.

Result-Blind Peer Reviews and Editorial Decisions

The present article suggests a possible way to reduce the file drawer problem in scientific research ( Rosenthal, 1978 , 1979 ), that is, the tendency for “nonsignificant” results to remain hidden in scientists’ file drawers because both authors and journals strongly prefer statistically significant results. We argue that peer-reviewed journals based on the principle of rigorous evaluation of research proposals before results are known would address this problem successfully. Even a single journal adopting a result-blind evaluation policy would remedy the persisting problem of publication bias more efficiently than other tools and techniques suggested so far. We also propose an ideal editorial policy for such a journal and discuss pragmatic implications and potential problems associated with this policy. Moreover, we argue that such a journal would be a valuable addition to the scientific publication outlets, because it supports a scientific culture encouraging the publication of well-designed and technically sound empirical research irrespective of the results obtained. Finally, we argue that such a journal would be attractive for scientists, publishers, and research agencies.

The impact of statins on psychological wellbeing: a systematic review and meta-analysis

BACKGROUND

Cholesterol-lowering medications such as statins have anti-inflammatory and antioxidant properties, which may be beneficial for treating depression and improving mood. However, evidence regarding their effects remains inconsistent, with some studies reporting links to mood disturbances. We aimed to conduct a meta-analysis to determine the impact of statins on psychological wellbeing of individuals with or without hypercholesterolemia.

METHODS

Articles were identified using medical, health, psychiatric and social science databases, evaluated for quality, and data were synthesized and analyzed in RevMan-5 software using a random effects model.

RESULTS

The 7 randomized controlled trials included in the analysis represented 2,105 participants. A test for overall effect demonstrated no statistically significant differences in psychological wellbeing between participants receiving statins or a placebo (standardized mean difference (SMD) = -0.08, 95% CI -0.29 to 0.12; P = 0.42). Sensitivity analyses were conducted to separately analyze depression (n = 5) and mood (n = 2) outcomes; statins were associated with statistically significant improvements in mood scores (SMD = -0.43, 95% CI -0.61 to -0.24).

CONCLUSIONS

Our findings refute evidence of negative effects of statins on psychological outcomes, providing some support for mood-related benefits. Future studies could examine the effects of statins in depressed populations.

Antibiotics versus placebo for acute bacterial conjunctivitis

BACKGROUND

Acute bacterial conjunctivitis is an infection of the conjunctiva. Both the palpebral and the bulbar ocular conjunctival surfaces are usually affected and typically become red and inflamed. Antibiotic therapy is widely used for the treatment of acute bacterial conjunctivitis. This Cochrane Review was first published in The Cochrane Library in 1999; updated in 2006 and again in 2012.

OBJECTIVES

To assess the benefits and harms of antibiotic therapy in the management of acute bacterial conjunctivitis.

SEARCH METHODS

We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (The Cochrane Library 2012, Issue 7), MEDLINE (January 1950 to July 2012), EMBASE (January 1980 to July 2012), OpenGrey (System for Information on Grey Literature in Europe) (www.opengrey.eu/), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrials.gov) and the WHO International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 18 July 2012.

SELECTION CRITERIA

We included double-masked randomised controlled trials (RCTs) in which any form of antibiotic treatment had been compared with placebo/vehicle in the management of acute bacterial conjunctivitis. This included topical, systemic and combination (for example, antibiotics and steroids) antibiotic treatments.

DATA COLLECTION AND ANALYSIS

Two authors (UN and SM) independently checked and reviewed the titles and abstracts of identified studies. We assessed the full text of all potentially relevant studies. We graded the included RCTs for methodological quality using Cochrane methodology. We performed data extraction in a standardised manner. We performed random-effects meta-analyses using RevMan.

MAIN RESULTS

We identified 11 eligible RCTs which randomised a total of 3673 participants. One further trial, which was published in abstract form in 1990 but has yet to be reported fully, is currently 'awaiting assessment'. Six of the 11 included studies have been included for the first time in this latest (2012) update. The trials were heterogeneous in terms of their inclusion and exclusion criteria, the nature of the intervention, and the outcome measures assessed. We judged two of the trials to be of high quality and graded the remainder as poor quality.Meta-analyses of data on clinical and microbiological remission rates revealed that topical antibiotics were of benefit in improving 'early' (days two to five) clinical (risk ratio (RR) 1.36, 95% confidence interval (CI) 1.15 to 1.61) and microbiological (RR 1.55, 95% CI 1.37 to 1.76) remission rates. At the 'late' time point (days six to 10), antibiotics were found to still confer modest benefits in clinical remission (RR 1.21, 95% CI 1.10 to 1.33) and microbiological cure rates (RR 1.37, 95% CI 1.24 to 1.52). By days six to 10, 41% (95% CI 38 to 43) of cases had resolved in those receiving placebo. We found no data on the cost-effectiveness of antibiotics. No serious outcomes were reported in either the active or placebo arms of these trials, suggesting that important sight-threatening complications are an infrequent occurrence.

AUTHORS' CONCLUSIONS

Although acute bacterial conjunctivitis is frequently self limiting, the findings from this updated systematic review suggest that the use of antibiotic eye drops is associated with modestly improved rates of clinical and microbiological remission in comparison to the use of placebo. Use of antibiotic eye drops should therefore be considered in order to speed the resolution of symptoms and infection.

Epidural pain relief versus systemic opioid-based pain relief for abdominal aortic surgery

BACKGROUND

Epidural analgesia offers greater pain relief compared to systemic opioid-based medications, but its effect on morbidity and mortality is unclear. This review was originally published in 2006 and was updated in 2011.

OBJECTIVES

To assess the benefits and harms of postoperative epidural analgesia in comparison with postoperative systemic opioid-based pain relief for adult patients who underwent elective abdominal aortic surgery.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2010, Issue 11) via Ovid; Ovid MEDLINE (from inception to week 1 November 2010); and EMBASE (from inception to week 1, November 2010). The original search was performed in 2004. We assessed non-English language reports and contacted researchers in the field. We did not seek unpublished data.

SELECTION CRITERIA

We included all randomized and quasi-randomized controlled trials comparing postoperative epidural analgesia and postoperative systemic opioid-based analgesia for adult patients who underwent elective open abdominal aortic surgery.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality and extracted data. We contacted study authors for additional information and data.

MAIN RESULTS

We included 15 trials that involved 1297 patients (633 patients received epidural analgesia and 664 received systemic opioid analgesia) in this review. This included one trial we found in our updated search and one trial from our original review that had been awaiting translation. The epidural analgesia group showed significantly lower visual analogue scale scores for pain on movement (up to postoperative day three) regardless of the site of the epidural catheter and epidural formulation. The postoperative duration of tracheal intubation and mechanical ventilation was significantly shorter, by about 48%, in the epidural analgesia group. The overall event rates of myocardial infarction, acute respiratory failure (defined as an extended need for mechanical ventilation), gastrointestinal complications, and renal complications were significantly lower in the epidural analgesia group.

AUTHORS' CONCLUSIONS

Epidural analgesia provides better pain relief (especially during movement) in the period up to three postoperative days. It reduces the duration of postoperative tracheal intubation by roughly half. The occurrence of prolonged postoperative mechanical ventilation, myocardial infarction, gastric complications and renal complications was reduced by epidural analgesia. However, current evidence does not confirm the beneficial effect of epidural analgesia on postoperative mortality and other types of complications.

Resistance training, visceral obesity and inflammatory response: a review of the evidence

Intra-abdominal obesity is an important risk factor for low-grade inflammation, which is associated with increased risk for diabetes mellitus and cardiovascular disease. For the most part, recommendations to treat or prevent overweight and obesity via physical activity have focused on aerobic endurance training as it is clear that aerobic training is associated with much greater energy expenditure during the exercise session than resistance training. However, due to the metabolic consequences of reduced muscle mass, it is understood that normal ageing and/or decreased physical activity may lead to a higher prevalence of metabolic disorders. Whether resistance training alters visceral fat and the levels of several pro-inflammatory cytokines produced in adipose tissue has not been addressed in earlier reviews. Because evidence suggests that resistance training may promote a negative energy balance and may change body fat distribution, it is possible that an increase in muscle mass after resistance training may be a key mediator leading to a better metabolic control. Considering the benefits of resistance training on visceral fat and inflammatory response, an important question is: how much resistance training is needed to confer such benefits? Therefore, the purpose of this review was to address the importance of resistance training on abdominal obesity, visceral fat and inflammatory response.

Meta-analysis of the association of CYP1A1 polymorphisms with gastric cancer susceptibility and interaction with tobacco smoking

The association of two cytochrome P4501A1 (CYP1A1) polymorphisms, m1 (T6235C transition) and m2 (A4889G transition), with gastric cancer risk is inconclusive. We conducted a meta-analysis of all available studies to evaluate the potential role of the polymorphisms and their interactions with tobacco smoking in gastric cancer susceptibility. Published literature from PubMed was retrieved by two investigators independently. Fourteen case-control studies with 2,032 gastric cancer cases and 5,099 controls were selected. A fixed effects model or a random-effects model was used to estimate the odds ratio (OR) for the CYP1A1 polymorphisms and the occurrence of gastric cancer. Significant associations between CYP1A1 m1 and m2 polymorphisms and gastric cancer susceptibility were not observed in all genetic models in the overall analyses. Subgroup analyses by ethnicity and source of controls did not reveal significant associations with gastric cancer risk. Stratification analysis by smoking status found that carriers of the heterozygous and homozygous m1 genotypes decreased the susceptibility of gastric cancer among ever-smokers (pooled OR = 0.56, 95 % CI 0.36-0.89, fixed effects). In contrast, the m2 genotypes (G/G and A/G) did not show any relevance to gastric cancer risk among the smoking population (pooled OR = 1.30, 95 % CI 0.84-2.00, fixed effects). Overall, we found that the CYP1A1 polymorphism itself, either m1 or m2, did not represent an independent genetic risk factor influencing gastric cancer. However, subgroup analyses suggest that carriers of the heterozygous and homozygous m1 genotype who are exposed to tobacco smoke have a significantly lower risk of developing gastric cancer. To explain the observed reduction of gastric cancer risk, we proposed a novel hypothesis of "observation bias". This hypothesis is also applicable to explain the combined effects of other genetic polymorphisms and environmental factors on the risk of developing cancers, and the rationality of the hypothesis needs to be further investigated.

Pelvic floor electrical stimulation for postprostatectomy urinary incontinence: a meta-analysis

OBJECTIVE

To evaluate the role of electrical stimulation (ES) in the recovery of postprostatectomy urinary incontinence (UI).

METHODS

We performed a meta-analysis of all available randomized controlled trials comparing ES enhanced pelvic floor muscle training (PFMT) with PFMT alone for postprostatectomy UI. We separated in the analysis the continence rate within 3 months or longer than 6 months after operation, which stand for the early and late recovery of UI after operation, respectively. Relative risk (RR) reductions and their 95% confidence intervals (CIs) were calculated for categorical outcomes.

RESULTS

Four studies randomizing 210 cases were included in the meta-analysis. Three studies enrolling 186 cases reported the continence rate within 3 months after radical prostatectomy. The pooled analysis did not show that ES improved early recovery of UI better than did PFMT (RR 1.21; 95% CI = 0.95-1.54, P = .12). All 4 studies provided data for 6-12 months after RP; the pooled analysis did not show a relative benefit (RR = 1.03; 95% CI = 0.88-1.20, P = .73).

CONCLUSION

Based on available evidence, ES enhanced PFMT did not improve the return to continence more than PFMT in men with postprostatectomy UI.

Publication bias in neuroimaging research: implications for meta-analyses

Neuroimaging and the neurosciences have made notable advances in sharing activation results through detailed databases, making meta-analysis of the published research faster and easier. However, the effect of publication bias in these fields has not been previously addressed or accounted for in the developed meta-analytic methods. In this article, we examine publication bias in functional magnetic resonance imaging (fMRI) for tasks involving working memory in the frontal lobes (Brodmann Areas 4, 6, 8, 9, 10, 37, 45, 46, and 47). Seventy-four studies were selected from the literature and the effect of publication bias was examined using a number of regression-based techniques. Pearson's r correlation coefficient and Cohen's d effect size estimates were computed for the activation in each study and compared to the study sample size using Egger's regression, Macaskill's regression, and the 'Trim and Fill' method. Evidence for publication bias was identified in this body of literature (p < 0.01 for each test), generally, though was neither task- nor sub-region-dependent. While we focused our analysis on this subgroup of brain mapping studies, we believe our findings generalize to the brain imaging literature as a whole and databases seeking to curate their collective results. While neuroimaging databases of summary effects are of enormous value to the community, the potential publication bias should be considered when performing meta-analyses based on database contents.

Metoclopramide for nausea and vomiting prophylaxis during and after Caesarean delivery: a systematic review and meta-analysis

Nausea and vomiting occur commonly during and after Caesarean delivery (CD) performed under neuraxial anaesthesia. Metoclopramide is a prokinetic agent reported to be safe in parturients. This meta-analysis assesses the efficacy of metoclopramide for prophylaxis against intra- and postoperative nausea and vomiting (IONV and PONV) in parturients undergoing CD under neuraxial anaesthesia. We performed a literature search of MEDLINE (1966-2011), Cochrane Central Register of Controlled Trials, EMBASE (1947-2011), Google scholar, and CINAHL for randomized controlled trials which compared metoclopramide with placebo in women having CD under neuraxial anaesthesia. Eleven studies with 702 patients were included in the analysis. Administration of metoclopramide (10 mg) resulted in a significant reduction in the incidence of ION and IOV when given before block placement [relative risk (RR) (95% confidence interval, 95% CI)=0.27 (0.16, 0.45) and 0.14 (0.03, 0.56), respectively] or after delivery [RR (95% CI)=0.38 (0.20, 0.75) and 0.34 (0.18, 0.66), respectively]. The incidence of early (0-3 or 0-4 h) PON and POV [RR (95% CI)=0.47 (0.26, 0.87) and 0.45 (0.21, 0.93), respectively] and overall (0-24 or 3-24 h) PON (RR 0.69; 95% CI 0.52, 0.92) were also reduced with metoclopramide. Extra-pyramidal side-effects were not reported in any patient. In conclusion, this review suggests that metoclopramide is effective and safe for IONV and PONV prophylaxis in this patient population. Given the quality of the studies and the infrequent use of neuraxial opioids, these results should be interpreted with caution in current practice and further studies are needed to confirm those findings.

Research methods for meta-analyses

Meta-analysis uses numerical tools to pool data and to estimate a summary effect size for the comparison of two interventions from a set of randomised controlled trials identified in a systematic review. An effect size is a single number that expresses the difference in outcome from the interventions. The most commonly used effect sizes for dichotomous outcomes, for example, mortality, are the odds ratio and the relative risk. The results of a meta-analysis are usually presented in a complex figure, known as a forest plot, which shows both the individual studies and the summary statistics. Sensitivity analyses are performed to clarify the effect of the experimental design bias on the effect size. Clinical and statistical heterogeneity of the included studies are explored by the additional tools of fixed effect versus random effects models and subgroup analyses.