Meta-analyses involving cross-over trials: methodological issues

Elbourne, Diana; Altman, Douglas G.; Higgins, Julian P T; Curtin, François; Worthington, Helen V; Vail, Andy

doi:10.1093/ije/31.1.140

Cited by 2,069 publications

(676 citation statements)

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“…We assessed for the presence of publication bias by using funnel plots and formal testing, which revealed weak evidence for an effect, strengthening the inferences from this review. An imputation approach for some comparisons was used to derive SEs for effect sizes; however, we took the most conservative approach by using the lowest correlation estimate among studies with all available data (26). The variability in measurement Figure 3.…”

Section: Discussionmentioning

confidence: 99%

“…When adequate data were reported, standardized mean differences (SMDs) were calculated as the mean difference in the biomechanical parameter between the insole and no-insole conditions, divided by the pooled SD, with adjustment for small sample sizes (Hedges g: SMD) (25). Where not reported, the SEM difference and correlations between outcomes were estimated from P values using the equivalent T statistic (26). When this was not possible, an imputation approach was taken where the SEM difference was estimated using the lowest correlation estimate from other studies (26).…”

Section: Significance and Innovationsmentioning

confidence: 99%

“…Where not reported, the SEM difference and correlations between outcomes were estimated from P values using the equivalent T statistic (26). When this was not possible, an imputation approach was taken where the SEM difference was estimated using the lowest correlation estimate from other studies (26). If more information was required from that provided in the paper, authors were contacted directly to provide necessary data (relevant data from 2 studies were provided immediately).…”

Section: Significance and Innovationsmentioning

confidence: 99%

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Lateral Wedge Insoles for Reducing Biomechanical Risk Factors for Medial Knee Osteoarthritis Progression: A Systematic Review and Meta‐Analysis

Arnold

Wong

Jones

et al. 2016

Arthritis Care & Research

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Objective. Lateral wedge insoles are intended to reduce biomechanical risk factors of medial knee osteoarthritis (OA) progression, such as increased knee joint load; however, there has been no definitive consensus on this topic. The aim of this systematic review and meta-analysis was to establish the within-subject effects of lateral wedge insoles on knee joint load in people with medial knee OA during walking. Methods. Six databases were searched from inception until February 13, 2015. Included studies reported on the immediate biomechanical effects of lateral wedge insoles during walking in people with medial knee OA. Primary outcomes of interest relating to the biomechanical risk of disease progression were the first and second peak external knee adduction moment (EKAM) and knee adduction angular impulse (KAAI). Eligible studies were pooled using random-effects metaanalysis.Results. Eighteen studies were included with a total of 534 participants. Lateral wedge insoles resulted in a small but statistically significant reduction in the first peak EKAM (standardized mean difference [SMD] 20.19; 95% confidence interval [95% CI] 20.23, 20.15) and second peak EKAM (SMD 20.25; 95% CI 20.32, 20.19) with a low level of heterogeneity (I 2 5 5% and 30%, respectively). There was a favorable but small reduction in the KAAI with lateral wedge insoles (SMD 20.14; 95% CI 20.21, 20.07, I 2 5 31%). Risk of methodologic bias scores (quality index) ranged from 8 to 13 out of 16. Conclusion. Lateral wedge insoles cause small reductions in the EKAM and KAAI during walking in people with medial knee OA. Current evidence demonstrates that lateral wedge insoles appear ineffective at attenuating structural changes in people with medial knee OA as a whole and may be better suited to targeted use in biomechanical phenotypes associated with larger reductions in knee load.

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Section: Discussionmentioning

confidence: 99%

Section: Significance and Innovationsmentioning

confidence: 99%

Section: Significance and Innovationsmentioning

confidence: 99%

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Lateral Wedge Insoles for Reducing Biomechanical Risk Factors for Medial Knee Osteoarthritis Progression: A Systematic Review and Meta‐Analysis

Arnold

Wong

Jones

et al. 2016

Arthritis Care & Research

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“…In crossover studies, it was recommended to extract paired t test data that evaluated the value of “measurement on intervention” minus “measurement on control” separately for each participant21; however, because these data were rarely provided, we resorted to using mean and SD separately for intervention and control. This step provided a conservative estimate of effect and reduced the power of crossover studies to show real effects of intervention 22. If SDs were not reported directly, we calculated them from SEM or 95% CI.…”

Section: Methodsmentioning

confidence: 99%

Effects of Vegetarian Diets on Blood Lipids: A Systematic Review and Meta‐Analysis of Randomized Controlled Trials

Wang

Zheng

Yang

et al. 2015

JAHA

266

187

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BackgroundVegetarian diets exclude all animal flesh and are being widely adopted by an increasing number of people; however, effects on blood lipid concentrations remain unclear. This meta‐analysis aimed to quantitatively assess the overall effects of vegetarian diets on blood lipids.Methods and ResultsWe searched PubMed, Scopus, Embase, ISI Web of Knowledge, and the Cochrane Library through March 2015. Studies were included if they described the effectiveness of vegetarian diets on blood lipids (total cholesterol, low‐density lipoprotein cholesterol, high‐density lipoprotein cholesterol, and triglyceride). Weighted mean effect sizes were calculated for net changes by using a random‐effects model. We performed subgroup and univariate meta‐regression analyses to explore sources of heterogeneity. Eleven trials were included in the meta‐analysis. Vegetarian diets significantly lowered blood concentrations of total cholesterol, low‐density lipoprotein cholesterol, high‐density lipoprotein cholesterol, and non–high‐density lipoprotein cholesterol, and the pooled estimated changes were −0.36 mmol/L (95% CI −0.55 to −0.17; P<0.001), −0.34 mmol/L (95% CI −0.57 to −0.11; P<0.001), −0.10 mmol/L (95% CI −0.14 to −0.06; P<0.001), and −0.30 mmol/L (95% CI −0.50 to −0.10; P=0.04), respectively. Vegetarian diets did not significantly affect blood triglyceride concentrations, with a pooled estimated mean difference of 0.04 mmol/L (95% CI −0.05 to 0.13; P=0.40).ConclusionsThis systematic review and meta‐analysis provides evidence that vegetarian diets effectively lower blood concentrations of total cholesterol, low‐density lipoprotein cholesterol, high‐density lipoprotein cholesterol, and non–high‐density lipoprotein cholesterol. Such diets could be a useful nonpharmaceutical means of managing dyslipidemia, especially hypercholesterolemia.

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“…The inverse variance method was used to calculate an overall effect (weighted mean difference) for each comparison of insulin regimens. For crossover studies only first-period data were included where available unless within-person differences with appropriate measures of dispersion were quoted or could be estimated from test statistics [29]. Data from three-arm trials were pooled such that each group only appeared once in any meta-analysis.…”

Section: Search Strategymentioning

confidence: 99%

Optimal insulin regimens in type 2 diabetes mellitus: systematic review and meta-analyses

et al. 2009

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Aims/hypothesis We compared the effect of biphasic, basal or prandial insulin regimens on glucose control, clinical outcomes and adverse events in people with type 2 diabetes. Methods We searched the Cochrane Library, MEDLINE, EMBASE and major American and European conference abstracts for randomised controlled trials up to October 2008. A systematic review and meta-analyses were performed. Results Twenty-two trials that randomised 4,379 patients were included. Seven trials reported both starting insulin dose and titration schedules. Hypoglycaemia definitions and glucose targets varied. Meta-analyses were performed pooling data from insulin-naive patients. Greater HbA 1c reductions were seen with biphasic and prandial insulin, compared with basal insulin, of 0.45% (95% CI 0.19-0.70, p=0.0006) and 0.45% (95% CI 0.16-0.73, p=0.002), respectively, but with lesser reductions of fasting glucose of 0.93 mmol/l (95% CI 0.21-1.65, p = 0.01) and 2.20 mmol/l (95% CI 1.70-2.70, p<0.00001), respectively. Larger insulin doses at study end were reported in biphasic and prandial arms compared with basal arms. No studies found differences in major hypoglycaemic events, but minor hypoglycaemic events for prandial and biphasic insulin were inconsistently reported as either higher than or equivalent to basal insulin. Greater weight gain was seen with prandial compared with basal insulin (1.86 kg, 95% CI 0.80-2.92, p=0.0006). Conclusions/interpretation Greater HbA 1c reduction may be obtained in type 2 diabetes when insulin is initiated using biphasic or prandial insulin rather than a basal regimen, but with an unquantified risk of hypoglycaemia. Studies with longer follow-up are required to determine the clinical relevance of this finding.

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Meta-analyses involving cross-over trials: methodological issues

Abstract: Methods do exist for including valuable information from two-period, two-treatment cross-over trials into quantitative reviews. However, poor reporting of cross-over trials will often impede attempts to perform a meta-analysis using the available methods.

Cited by 2,069 publications

References 24 publications

Lateral Wedge Insoles for Reducing Biomechanical Risk Factors for Medial Knee Osteoarthritis Progression: A Systematic Review and Meta‐Analysis

Lateral Wedge Insoles for Reducing Biomechanical Risk Factors for Medial Knee Osteoarthritis Progression: A Systematic Review and Meta‐Analysis

Effects of Vegetarian Diets on Blood Lipids: A Systematic Review and Meta‐Analysis of Randomized Controlled Trials

Optimal insulin regimens in type 2 diabetes mellitus: systematic review and meta-analyses

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