Sensitivity of between-study heterogeneity in meta-analysis: proposed metrics and empirical evaluation

Uncoupling protein 2 gene polymorphisms in association with overweight and obesity susceptibility: A meta-analysis

A meta-analysis was performed to evaluate the associations of uncoupling protein 2 (UCP2) gene polymorphisms (Ala55Val, 45-bp insertion/deletion, and -866G/A) with overweight and obesity. A total of 42 studies were included in our analysis. Pooled effect estimates and 95% confidential intervals of each polymorphism were calculated under different inherited models. Fixed or random effect model was selected based on the between-study heterogeneity evaluated with I². Source of heterogeneity was explored by subgroup analysis and meta-regression analysis. Potential publication bias was assessed using funnel plot and Peters test. After excluding studies that deviated from the Hardy–Weinberg equilibrium, T allele of Ala55Val polymorphism was associated with an increased risk of overweight and obesity under recessive model in the overall (OR = 1.24, 95%CI = 1.06–1.45) and Asian (OR = 1.28, 95%CI = 1.06–1.55) populations; and A allele of -866G/A polymorphism had a protective effect on overweight and obesity, especially for European populations (dominant model: OR = 0.88, 95%CI = 0.81–0.96, co-dominant 1 model: OR = 0.89, 95%CI = 0.81–0.98, co-dominant 2 model: OR = 0.85, 95%CI = 0.74–0.94, additive model: OR = 0.88, 95%CI = 0.80–0.95, and allelic model: OR = 0.91, 95%CI = 0.86–0.97). No evidence was observed in the association of 45-bp insertion/deletion polymorphism with overweight and obesity susceptibility. We failed to fully explore the between-study heterogeneity regarding the association of Ala55Val polymorphism with overweight and obesity. Further studies are required to provide more convincing evidence.

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We evaluated the association of UCP2 gene polymorphisms with overweight and obesity.

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Ala55Val polymorphism was associated with an increased risk in Asian populations.

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No association was observed for 45-bp insertion/deletion polymorphism.

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-866G/A polymorphism was associated with a decreased risk in European populations.

Polymorphisms of C242T and A640G in CYBA gene and the risk of coronary artery disease: a meta-analysis

Background

Coronary artery disease (CAD) is a leading cause of mortality in many countries. Considerable studies have been carried out to investigate the relationship between the C242T and A640G polymorphisms of CYBA gene and CAD, but the results were still inconsistent. Hence we conducted a meta-analysis to clarify the association.

Methods and Results

A total of 21 eligible literatures were included in the meta-analysis. We observed a significant decreased risk of CAD for C242T polymorphism in Asian population under an allelic model (OR 0.75; 95% CI 0.67–0.84) and a dominant model (OR 0.69; 95% CI 0.61–0.79), however, in overall population and other population no significant association was revealed. We also found A640G polymorphism may contribute to reducing CAD risk under an allelic model (OR 0.84; 95% CI 0.75–0.93), dominant model (OR0.77; 95% CI 0.64–0.92) and recessive model (OR0.82; 95% CI 0.69–0.97). No publication bias was found.

Conclusion

Our meta-analysis confirmed a protective effect of C242Tpolymorphism on CAD in Asian population and indicated that A640G polymorphism was significantly associated with decreased risk of CAD.

Association of VEGF gene polymorphisms with diabetic retinopathy: a meta-analysis

Background

Studies on the association of vascular endothelial growth factor (VEGF) gene -460T/C and -2578C/A polymorphisms with diabetic retinopathy (DR) have reported conflicting results. The aim of the present study was to assess the association by using meta-analysis.

Methods

A systematic search of electronic databases (PubMed, EMBASE, Elsevier Science Direct, ISI Web of Science, CBM, CNKI and VIP) was carried out until Sept 18, 2013. The pooled odds ratios (ORs) and their corresponding 95% confidence intervals (CIs) were used to assess the strength of the association.

Results

Eleven studies (-460T/C: 6 studies including 932 cases and 722 controls; -2578C/A: 6 studies including 1,071 cases and 1,137 controls) were involved in this meta-analysis. Significant association was found for -460T/C polymorphism (C versus T: OR=1.48, 95%CI=1.07–2.05, P=0.02; TC+CC versus TT: OR=1.78, 95%CI=1.02–3.12, P=0.04; CC versus TT+TC: OR=1.76, 95%CI=1.10–2.81, P=0.02), but not for -2578C/A polymorphism (P>0.05). Similar results were found in the subgroup analysis.

Conclusions

This meta-analysis demonstrates that DR is associated with VEGF gene -460T/C polymorphism, but not -2578C/A polymorphism. Further case-control studies based on larger sample size are still needed, especially for -2578C/A polymorphism.

Hepatitis C virus infection and risk of stroke: a systematic review and meta-analysis

BACKGROUND/AIMS

Several studies analyzed the association between hepatitis C virus (HCV) infection and the risk of stroke or cerebrovascular death, but their findings were inconsistent. Up to date, no systematic review about the association between HCV infection and stroke was performed. We conducted a meta-analysis to examine whether HCV infection dose increase stroke risk in comparison to the population without HCV infection.

METHODS

We followed standard guidelines for performance of meta-analysis. Two independent investigators identified eligible studies through structured keyword searches in several databases. Random-effects and fixed-effects models were used to synthesize the data. Heterogeneity between studies and publication bias were also accessed.

RESULTS

Combining the data from the eligible studies, we calculated the pooled multi-factor adjusted Odds Ratio (OR) with 95% confidence interval (CI). Upon the heterogeneity found between studies, the result was 1.58 (0.86, 2.30) by random-effects model. However, after omitting the study which induced heterogeneity, the pooled OR with 95% CI was 1.97 (1.64, 2.30).

CONCLUSIONS

This meta-analysis suggested that HCV infection increased the risk of stroke. More prospective cohort studies will be needed to confirm this association with underlying biological mechanisms in the future.

Hepatitis C virus infection and risk of stroke: a systematic review and meta-analysis

BACKGROUND/AIMS

Several studies analyzed the association between hepatitis C virus (HCV) infection and the risk of stroke or cerebrovascular death, but their findings were inconsistent. Up to date, no systematic review about the association between HCV infection and stroke was performed. We conducted a meta-analysis to examine whether HCV infection dose increase stroke risk in comparison to the population without HCV infection.

METHODS

We followed standard guidelines for performance of meta-analysis. Two independent investigators identified eligible studies through structured keyword searches in several databases. Random-effects and fixed-effects models were used to synthesize the data. Heterogeneity between studies and publication bias were also accessed.

RESULTS

Combining the data from the eligible studies, we calculated the pooled multi-factor adjusted Odds Ratio (OR) with 95% confidence interval (CI). Upon the heterogeneity found between studies, the result was 1.58 (0.86, 2.30) by random-effects model. However, after omitting the study which induced heterogeneity, the pooled OR with 95% CI was 1.97 (1.64, 2.30).

CONCLUSIONS

This meta-analysis suggested that HCV infection increased the risk of stroke. More prospective cohort studies will be needed to confirm this association with underlying biological mechanisms in the future.

PAI-1 -675 4G/5G polymorphism in association with diabetes and diabetic complications susceptibility: a meta-analysis study

A meta-analysis was performed to assess the association between the PAI-1 -675 4G/5G polymorphism and susceptibility to diabetes mellitus (DM), diabetic nephropathy (DN), diabetic retinopathy (DR) and diabetic coronary artery disease (CAD). A literature-based search was conducted to identify all relevant studies. The fixed or random effect pooled measure was calculated mainly at the allele level to determine heterogeneity bias among studies. Further stratified analyses and sensitivity analyses were also performed. Publication bias was examined by the modified Begg’s and Egger’s test. Twenty published articles with twenty-seven outcomes were included in the meta-analysis: 6 studies with a total of 1,333 cases and 3,011 controls were analyzed for the PAI-1 -675 4G/5G polymorphism with diabetes risk, 7 studies with 1,060 cases and 1,139 controls for DN risk, 10 studies with 1,327 cases and 1,557 controls for DR and 4 studies with 610 cases and 1,042 controls for diabetic CAD risk respectively. Using allelic comparison (4G vs. 5G), the PAI-1 -675 4G/5G polymorphism was observed to have no significant association with diabetes (REM OR 1.07, 95% CI 0.96, 1.20), DN (REM OR 1.10, 95% CI 0.98, 1.25), DR (REM OR 1.09, 95% CI 0.97, 1.22) or diabetic CAD risk (REM OR 1.07, 95% CI 0.81, 1.42), and similar results were obtained in the dominant, recessive and co-dominant models. Our meta-analyses suggest that the PAI-1 -675 4G/5G polymorphism might not be a risk factor for DM, DN, DR or diabetic CAD risk in the populations investigated. This conclusion warrants confirmation by further studies.

Diabetes mellitus increases the risk of bladder cancer: an updated meta-analysis of observational studies

BACKGROUND

Increasing evidence suggests that diabetes mellitus (DM) may be associated with an increased risk of bladder cancer. We performed an updated meta-analysis to examine the association between DM and risk of bladder cancer.

MATERIALS AND METHODS

We systematically searched the EMBASE and Medline (PubMed) databases (from inception through February 1, 2013) and reviewed the reference lists of relevant publications to search for additional studies. Summary relative risks (RRs) with 95% confidence intervals (CIs) were calculated with random-effects models.

RESULTS

In total, 10 case-control and 14 cohort studies met the inclusion criteria. Analysis of all studies showed that DM was associated with an increased risk of bladder cancer (RR 1.30, 95% CI 1.18-1.43). There was heterogeneity among studies (Pheterogeneity <0.001, I(2)=81.5%). Cohort studies showed a lower risk (RR 1.23, 95% CI 1.09-1.37) than case-control studies (odds ratio 1.46, 95% CI 1.20-1.78). The positive association was significant only in women (RR 1.23, 95% CI 1.02-1.49), but not in men (RR 1.07, 95% CI 0.97-1.18). The combined RRs remained unchanged before and after the studies on type 1 diabetes were excluded from analysis. The association between DM and bladder cancer risk did not differ significantly by methods of DM ascertainment. The combined RRs were 1.17 (95% CI 1.03-1.34), 1.34 (95% CI 1.19-1.51), and 1.57 (95% CI 0.96-2.55), respectively, when restricting the analysis to the studies accounting for body mass index, cigarette smoking, or glucose-lowering drug use.

CONCLUSIONS

This meta-analysis indicates a positive association between DM and risk of bladder cancer. Further studies are warranted to determine whether DM prevention and control can reduce risk of bladder cancer.

Association of inorganic arsenic exposure with type 2 diabetes mellitus: a meta-analysis

BACKGROUND

The association of long-term effects of inorganic arsenic (iAs) exposure with type 2 diabetes mellitus (T2DM) risk remains controversial.

METHODS

A literature search was performed in PubMed, China National Knowledge Infrastructure and Web of Knowledge for relevant available articles published in English or Chinese from 1 January 1990 to 5 June 2013. Case-control, cohort or cross-sectional studies evaluating iAs and T2DM were included. The DerSimonian and Laird random effect model was adopted as the pooling method. Dose-response relationship was assessed by restricted cubic spline model and multivariate random-effect meta-regression.

RESULTS

Of the 569 articles identified through searching databases, 17 published articles with 2,243,745 participants for iAs in drinking water and 21 083 participants for total arsenic (tAs) in urine were included for this meta-analysis. The pooled relative risk with 95% CI of T2DM for the highest versus lowest category of iAs exposure level in drinking water was 1.75 (1.20 to 2.54). After removing three studies that had a strong effect on heterogeneity, the pooled relative risk was 1.23 (1.12 to 1.36). Dose-response analysis suggested T2DM risk increased by 13% (1.13 (1.00 to 1.27)) for every 100 µg/L increment of iAs in drinking water. Significant association of T2DM risk with tAs in urine was also found 1.28 (1.14 to 1.44).

CONCLUSIONS

This meta-analysis indicates that long-term iAs exposure might be positively associated with T2DM risk.

Association of the rs7903146 polymorphism in transcription factor 7-like 2 (TCF7L2) gene with gestational diabetes mellitus: a meta-analysis

A meta-analysis was performed to assess the association between the transcription factor 7-like 2 (TCF7L2) gene polymorphism rs7903146 (IVS3C > T) and gestational diabetes mellitus (GDM). A comprehensive search was conducted to identify all case-control or cohort design studies of the above-mentioned associations. The fixed or random effect pooled measure was selected on the basis of homogeneity test among studies. Heterogeneity among studies was evaluated using the I(2). Meta-regression was used to explore the potential sources of between-study heterogeneity. Publication bias was estimated using Egger's linear regression test. A total of 10 studies including 3404 cases and 6473 controls were involved in this meta-analysis. Overall, after excluding articles that deviated from HWE in controls, and further the key contributors to between-study heterogeneity, significant associations between TCF7L2 rs7903146 genetic polymorphism and risk of gestational diabetes mellitus were observed in the dominant (OR 1.653, 95% CI 1.416-1.930) and codominant (OR 1.525, 95% CI 1.350-1.723) models. The meta-analysis suggests that TCF7L2 rs7903146 genetic polymorphism was associated with increased risk of gestational diabetes mellitus.

The role of adiponectin in breast cancer: a meta-analysis

Published results suggests that high adiponectin level may decrease the risk of breast cancer. However, available evidence on breast cancer is conflicting. Therefore a meta-analysis was performed to assess the association between blood adiponectin and breast cancer risk. PubMed database, Web of Science, Elsevier Science, Springer Link and bibliographies of retrieved articles were searched for epidemiological studies published up to March 2013. Meta-analysis was performed on the combined effect values (OR) as well as standardized mean difference (SMD) including 17 studies. Fixed or random effect pooled measure was selected on the basis of homogeneity test among studies. The publication bias was assessed by the Egger's regression asymmetry test and Begg's rank correlation test with Begg's funnel plot. Subgroup analyses and sensitivity analysis were also performed. A total of 13 studies involving 3578 breast cancer cases and 4363 controls contributed to the OR analysis. The high adiponectin level did not significantly affect breast cancer risk (OR=0.902, 95% CI=0.773-1.053). After excluding articles that were the key contributors to between-study heterogeneity, the OR of high adiponectin level was associated with decreased breast cancer risk (OR=0.838, 95% CI=0.744-0.943). There was a significantly association between high adiponectin level and postmenopausal breast cancer women (OR=0.752, 95%CI=0.604-0.936); and it was not associated with premenopausal breast cancer women (OR=0.895, 95%CI=0.638-1.256). The result of pooled measure on SMD was that the high adiponectin level was associated with decreased breast cancer risk (SMD= -0.348, 95% CI= -0.533--0.614) after excluding articles which were the key contributors to between-study heterogeneity. Our findings indicate that high adiponectin level might decrease the risk of postmenopausal breast cancer. More randomized clinical trials and observational studies are needed to confirm this association with underlying biological mechanisms in the future.

WITHDRAWN: Uncoupling protein 2 gene polymorphisms in association with overweight and obesity susceptibility: A meta-analysis

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Meta-analysis of the association between urokinase-plasminogen activator gene rs2227564 polymorphism and Alzheimer's disease

OBJECTIVE

The association between urokinase-plasminogen activator (PLAU) gene rs2227564 polymorphism and Alzheimer's disease (AD) risk has been widely reported across different ethnic populations, with inconsistent results. Thus, we performed a meta-analysis to assess the association between PLAU rs2227564 polymorphism and AD risk.

METHODS

Fixed or random effect model was used as the pooling method to assess the basis of homogeneity test among studies. Summarized estimation of odds ratio (OR) and 95% confidence interval (CI) were calculated. Heterogeneity among studies was evaluated using Q test and I (2). Publication bias was estimated using Harbord's test.

RESULTS

A total of 27 studies (comprising 6100 AD cases and 5718 controls) were included in this meta-analysis. The present meta-analysis showed a significant increased effect of T allele on risk of AD in dominant model (fixed effect model [FEM] OR 1.123, 95% CI 1.025-1.231) and heterozygote comparison (CT vs CC; FEM OR 1.126, 95% CI 1.027-1.235). No publication bias was detected.

CONCLUSION

This meta-analysis showed that T allele of rs2227564 polymorphism in PLAU gene could increase the effects on risk of AD, and this result needs to be confirmed by further studies.

Serum uric acid levels and incidence of impaired fasting glucose and type 2 diabetes mellitus: a meta-analysis of cohort studies

AIMS

A meta-analysis of cohort studies was conducted to assess the association between serum uric acid (SUA) levels and incidence of impaired fasting glucose (IFG) and type 2 diabetes mellitus (T2DM).

METHODS

A comprehensive search was conducted to identify eligible studies. The fixed or random effect pooled measure was selected based on between-study heterogeneity. Dose-response relationship was assessed by restricted cubic spline model and multivariate random-effect meta-regression.

RESULTS

Twelve studies with fifteen results were included involving 6340 cases and 62,834 participants. The pooled multivariate-adjusted relative risk (RR) (95%CI) of IFG and T2DM for the highest vs. lowest level of SUA was 1.54 (1.41-1.68), I(2)=42.2%. The association was consistent and significant across subgroup analysis. A nonlinear relationship was found of SUA levels with incidence of IFG and T2DM (P<0.01), and the multivariate-adjusted RRs (95%CI) of IFG and T2DM were 1.02 (0.95-1.10), 1.04 (0.94-1.15), 1.10 (0.99-1.22), 1.25 (1.16-1.35), 1.43 (1.31-1.55), 1.50 (1.38-1.63) and 1.49 (1.34-1.67) for 2.5, 3.5, 4.5, 5.5, 6.5, 7.5 and 8.5mg/dl of SUA. The RR (95%CI) of T2DM for the highest vs. lowest level of SUA was 1.67 (1.51-1.86), and a nonlinear relationship was also found between SUA levels and incidence of T2DM.

CONCLUSIONS

SUA levels are positively associated with incidence of IFG and T2DM, and the association might be nonlinear.

The MPO-463G>A polymorphism and lung cancer risk: a meta-analysis based on 22 case-control studies

Background

Myeloperoxidase (MPO) is an endogenous oxidant enzyme that produces reactive oxygen species (ROS) and may be involved in lung carcinogenesis. The MPO−463G>A polymorphism influences MPO transcription and has been associated with lung cancer susceptibility. However, the association between the MPO−463G>A polymorphism and lung cancer risk remains controversial.

Method

To investigate the effect of this polymorphism on lung cancer susceptibility, we performed a meta-analysis based on 22 published case–control studies including 7,520 patients with lung cancer and 8,600 controls. Odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the strength of the association.

Results

Overall, there was no evidence for significant association between MPO−463G>A polymorphism and lung cancer susceptibility (for AA versus GG: OR = 0.91, 95%CI = 0.67–1.24; for GA versus GG: OR = 0.87, 95% CI = 0.78–0.98; for AA/GA versus GG: OR = 0.90, 95% CI = 0.80–1.01; for AA versus GA/GG: OR = 0.96, 95% CI = 0.72–1.28). In the stratified analyses by ethnicity, source of controls and smoking status, we also did not find any significant association between them.

Conclusions

In summary, this meta-analysis suggests MPO−463G>A polymorphism may not be a risk factor for developing lung cancer. However, further prospective well-designed population-based studies with larger sample size are expected to validate the results.

Black tea, green tea and risk of breast cancer: an update

Previous meta-analysis indicated conflicting results in case–control versus cohort studies on the association of green tea with breast cancer risk, and conflicting results were also found in case–control versus cohort studies in another meta-analysis on the association of black tea with breast cancer risk. Many studies were published after the previous meta-analysis. Besides, the dose-response relationship of tea consumption with breast cancer risk is unclear. Thus the association of tea consumption with breast cancer risk was assessed incorporating new publications. Summary relative risk (RR) for highest versus lowest level of tea consumption was calculated based on fixed or random effect models. Dose-response relationship was assessed by restricted cubic spline model and multivariate random-effect meta-regression. The combined results from 9 studies suggested no significant association between green tea consumption and breast cancer risk (RR = 0.82, 95% CI = 0.64-1.04). No significant association was found among cohort studies and case-control studies after sensitivity analysis, respectively. A linear but not significant dose-response association was found between green tea consumption and breast cancer risk. The combined results from 25 studies demonstrated no significant association between black tea consumption and breast cancer risk (RR = 0.98, 95% CI = 0.93-1.03), and no significant association was found in subgroup analysis. A linear but not significant dose-response association was found between black tea consumption and breast cancer risk. Based on the current evidence, black tea and green tea might not contribute significantly to breast cancer risk, respectively.

Orthostatic hypotension and the risk of congestive heart failure: a meta-analysis of prospective cohort studies

BACKGROUND

Orthostatic hypotension (OH) has been related to the increased risk of future congestive heart failure (CHF) events. However, the overall quantitative estimate of predictive ability of OH for CHF has not been determined. We therefore performed a meta-analysis to investigate the association between OH and incident CHF.

METHODS

Prospective cohort studies relevant to the aim of the study were identified by searching of Medline and Embase databases up to December 25, 2012 without restrictions and by reviewing the reference lists from retrieved articles.

RESULTS

A total of 51270 subjects and 3603 incident CHF cases from 4 prospective cohorts were included in the meta-analysis. Using random effect model, the pooled result indicated that presence of OH at baseline was significantly associated with an increased risk for future CHF outcomes (adjusted hazard ratio: 1.30, 95% confidence interval 1.09-1.55; p = 0.004). Results of stratified analysis suggested that the association between OH and CHF incidence seemed to be significant in middle-age subjects, or the individuals with hypertension and diabetes at baseline, but did not significant in the elderly subjects or those without hypertension or diabetes.

CONCLUSIONS

Our meta-analysis confirmed that presence of OH is related to a significant increased risk for development of CHF in the future. Studies are needed to explore the potential mechanisms underlying this association. More importantly, screen for OH may be of great clinical significance for the early identification of subjects at higher risk for development of CHF.

Intraoperative radiotherapy in colorectal cancer: systematic review and meta-analysis of techniques, long-term outcomes, and complications

BACKGROUND

The precise contribution of IORT to the management of locally advanced and recurrent colorectal cancer (CRC) remains uncertain. We performed a systematic review and meta-analysis to assess the value of IORT in this setting.

METHODS

Studies published between 1965 and 2011 that reported outcomes after IORT for advanced or recurrent CRC were identified by an electronic literature search. Studies were assessed for methodological quality and design, and evaluated for technique of IORT delivery, oncological outcomes, and complications following IORT. Outcomes were analysed with fixed-effect and random-effect model meta-analyses and heterogeneity and publication bias examined.

RESULTS

29 studies comprising 14 prospective and 15 retrospective studies met the inclusion criteria and were assessed, yielding a total of 3003 patients. The indication for IORT was locally advanced disease in 1792 patients and locally recurrent disease in 1211 patients. Despite heterogeneity in methodology and reporting practice, IORT is principally applied for the treatment of close or positive margins. When comparative studies were evaluated, a significant effect favouring improved local control (OR 0.22; 95% CI = 0.05-0.86; p = 0.03), disease free survival (HR 0.51; 95% CI = 0.31-0.85; p = 0.009), and overall survival (HR 0.33; 95% CI = 0.2-0.54; p = 0.001) was noted with no increase in total (OR 1.13; 95% CI = 0.77-1.65; p = 0.57), urologic (OR 1.35; 95% CI = 0.84-2.82; p = 0.47), or anastomotic complications (OR 0.94; 95% CI = 0.42-2.1; p = 0.98). Increased wound complications were noted after IORT (OR 1.86; 95% CI = 1.03-3.38; p = 0.049).

CONCLUSIONS

Despite methodological weaknesses in the studies evaluated, our results suggest that IORT may improve oncological outcomes in advanced and recurrent CRC.

Association of the C677T polymorphism in the MTHFR gene with hemorrhagic stroke: a meta-analysis

AIMS

We performed a meta-analysis to assess the possible association between the MTHFR gene C677T polymorphism and hemorrhagic stroke.

METHODS

A comprehensive search was conducted to identify all case-control or cohort design studies of the associations between C677T and HS. The fixed or random effect pooled measure was selected on the basis of a homogeneity test among studies. Heterogeneity among studies was evaluated using the I(2). Meta-regression and the "leave-one-out" sensitive analysis of Patsopoulos et al. were used to explore potential sources of between-study heterogeneity. Publication bias was estimated using the Begg's test.

RESULTS

Fifteen case-control studies corresponded to the inclusion criteria, including 2034 cases and 4485 controls for the present meta-analysis. After excluding articles that deviated from the Hardy-Weinberg equilibrium in controls and the key contributors to between-study heterogeneity, significant associations between the MTHFR C677T genetic polymorphism and the risk of hemorrhagic stroke were observed in dominant (Odds ratio [OR] 1.611, 95% confidence interval [CI] 1.336-1.942), codominant (OR 1.500, 95% CI 1.330-1.692), and recessive (OR 1.695, 95% CI 1.409-2.038) models.

CONCLUSIONS

The meta-analysis suggests that the MTHFR C667T genetic polymorphism was associated with increased risk of hemorrhagic stroke, and the T allele may be an important risk factor for hemorrhagic stroke. The findings are of importance to the genetic epidemiology of hemorrhagic stroke, and to explore genetic diagnosis, treatment, and prevention of hemorrhagic stroke.

Rs143383 in the growth differentiation factor 5 (GDF5) gene significantly associated with osteoarthritis (OA)-a comprehensive meta-analysis

Family, twin, adoption studies show osteoarthritis (OA) has a substantial genetic component. Several studies have shown an association between OA and Growth Differentiation Factor 5 (GDF5), some others have not. Thus, the status of the OA-GDF5 association is uncertain. This meta-analysis was applied to case-control studies of the association between OA and GDF5 to assess the joint evidence for the association, the influence of individual studies, and evidence for publication bias. Relevant studies were identified from the following electronic databases: MEDLINE and current contents before Feb. 2012. For the case-control studies, the authors found 1) support for the association between OA and GDF5. The rs143383 polymorphism was significantly associated with OA [fixed: OR and 95% CI: 1.193 (1.139-1.249), p < 0.001; random: OR and 95% CI: 1.204 (1.135-1.276), p < 0.001], 2) no evidence that this association was accounted for by any one study, and 3) no evidence for publication bias. Although the effect size of the association between OA and GDF5 is small, there is suggestive evidence for an association. Further studies are needed to clarify what variant of GDF5 (or some nearby gene) accounts for this association.

GPX1 gene Pro200Leu polymorphism, erythrocyte GPX activity, and cancer risk

A meta-analysis was conducted to assess the effect of glutathione peroxidase1 (GPX1) gene Pro200Leu (rs1050450) polymorphism on cancer risk. A comprehensive search was performed to identify all studies on the association of GPX1 gene Pro200Leu polymorphism with cancer risk. The fixed or random effect pooled measure was selected based on homogeneity test among studies. Heterogeneity among studies was evaluated using the I (2). Potential sources of between-study heterogeneity were explored by meta-regression and the sensitivity analysis. Publication bias was estimated using Egger's linear regression test. 35 published articles with 36 results were identified involving 16,920 cases and 19,946 controls. Results from the articles that both obeyed Hardy-Weinberg equilibrium in controls and met high quality design, showed no significant association of GPX1 gene Pro200Leu polymorphism with cancer risk in any of dominant (OR = 1.05, 95 %CI = 0.98-1.12), recessive (OR = 1.04 (0.95-1.13), and TT versus CC (OR = 1.05, 95 %CI = 0.97-1.15) models, and the findings were consistent considering the stratified analysis by cancer type. However, multivariate-adjusted ORs from articles that both obeyed Hardy-Weinberg equilibrium in controls and met high quality design, showed a significant association considering dominant (OR = 1.22, 95 %CI = 1.06-1.41), TT versus CC (OR = 1.16, 95 %CI = 1.02-1.32) models, and a marginally significant association was found considering TC versus CC (OR = 1.11, 95 %CI = 0.99-1.25) model. And compared with the CC genotype, the erythrocyte GPX activity was significantly lower for TT genotype: the standardized mean difference (SMD) = -0.37, 95 %CI = (-0.624, -0.118), and CT genotype: SMD = -0.19, 95 %CI = (-0.37, -0.002). The association of GPX1 gene Pro200Leu polymorphism with cancer risk might be influenced by confounders.

Association of all-cause mortality with overweight and obesity using standard body mass index categories: a systematic review and meta-analysis

IMPORTANCE

Estimates of the relative mortality risks associated with normal weight, overweight, and obesity may help to inform decision making in the clinical setting.

OBJECTIVE

To perform a systematic review of reported hazard ratios (HRs) of all-cause mortality for overweight and obesity relative to normal weight in the general population.

DATA SOURCES

PubMed and EMBASE electronic databases were searched through September 30, 2012, without language restrictions.

STUDY SELECTION

Articles that reported HRs for all-cause mortality using standard body mass index (BMI) categories from prospective studies of general populations of adults were selected by consensus among multiple reviewers. Studies were excluded that used nonstandard categories or that were limited to adolescents or to those with specific medical conditions or to those undergoing specific procedures. PubMed searches yielded 7034 articles, of which 141 (2.0%) were eligible. An EMBASE search yielded 2 additional articles. After eliminating overlap, 97 studies were retained for analysis, providing a combined sample size of more than 2.88 million individuals and more than 270,000 deaths.

DATA EXTRACTION

Data were extracted by 1 reviewer and then reviewed by 3 independent reviewers. We selected the most complex model available for the full sample and used a variety of sensitivity analyses to address issues of possible overadjustment (adjusted for factors in causal pathway) or underadjustment (not adjusted for at least age, sex, and smoking).

RESULTS

Random-effects summary all-cause mortality HRs for overweight (BMI of 25-<30), obesity (BMI of ≥30), grade 1 obesity (BMI of 30-<35), and grades 2 and 3 obesity (BMI of ≥35) were calculated relative to normal weight (BMI of 18.5-<25). The summary HRs were 0.94 (95% CI, 0.91-0.96) for overweight, 1.18 (95% CI, 1.12-1.25) for obesity (all grades combined), 0.95 (95% CI, 0.88-1.01) for grade 1 obesity, and 1.29 (95% CI, 1.18-1.41) for grades 2 and 3 obesity. These findings persisted when limited to studies with measured weight and height that were considered to be adequately adjusted. The HRs tended to be higher when weight and height were self-reported rather than measured.

CONCLUSIONS AND RELEVANCE

Relative to normal weight, both obesity (all grades) and grades 2 and 3 obesity were associated with significantly higher all-cause mortality. Grade 1 obesity overall was not associated with higher mortality, and overweight was associated with significantly lower all-cause mortality. The use of predefined standard BMI groupings can facilitate between-study comparisons.

Physical activity and risk of breast cancer: a meta-analysis of prospective studies

We conducted a meta-analysis to summarize the evidence from prospective studies regarding the association between physical activity and breast cancer risk. A comprehensive search was conducted to identify eligible studies. The fixed or random effect model was used based on heterogeneity test. The dose-response relationship was assessed by restricted cubic spline model and multivariate random-effect meta-regression. Overall, 31 studies with 63,786 cases were included, and the combined relative risk (RR) with 95 % CI of breast cancer was 0.88 (0.85-0.91). In subgroup analysis by activity type, data from 27 studies including 37,568 cases for non-occupational activity (including recreational activity and household activity) and seven studies including 28,268 cases for occupational activity were used, and the RR (95 % CI) of breast cancer was 0.87 (0.83-0.91) and 0.90 (0.83-0.97), respectively. The inverse association was consistent among all subgroups analyses. Stronger association was found for subjects with BMI <25 kg/m(2) [0.72 (0.65-0.81)], premenopausal women [0.77 (0.72-0.84)], and estrogen and progesterone receptor-negative breast cancer [0.80 (0.73-0.87)]. Dose-response analysis suggested that the risk of breast cancer decreased by 2 % (P < 0.00) for every 25 metabolic equivalent (MET)-h/week increment in non-occupational physical activity, 3 % (P < 0.00) for every 10 MET-h/week (roughly equivalent to 4 h/week of walking in 2 miles/h or 1 h/week of running in 6 miles/h) increment in recreational activity, and 5 % (P < 0.00) for every 2 h/week increment in moderate plus vigorous recreational activity, respectively. Physical activity could significantly reduce the risk of breast cancer.

Fish consumption, omega-3 fatty acids and risk of heart failure: a meta-analysis

BACKGROUND & AIMS

While marine omega-3 fatty acids have been associated with a lower mortality in heart failure patients, data on omega-3 and incident heart failure are inconsistent. We systematically reviewed the evidence on the association of omega-3 fatty acids and fish intake with the incidence of heart failure in this meta-analysis.

METHODS

We identified relevant studies by searching MEDLINE and EMBASE databases up to August 31, 2011 without restrictions and by reviewing reference lists from retrieved articles.

RESULTS

A total of 176,441 subjects and 5480 incident cases of heart failure from 7 prospective studies were included in this analysis. Using random effect model, the pooled relative risk for heart failure comparing the highest to lowest category of fish intake was 0.85 (95% CI; 0.73-0.99), p = 0.04; corresponding value for marine omega-3 fatty acids was 0.86 (0.74-1.00), p = 0.05. There was no evidence for heterogeneity across studies of fish consumption (I(2) = 8%). In contrast, there was modest heterogeneity for omega-3 fatty acid analysis (I(2) = 44%). Lastly, there was no evidence for publication bias.

CONCLUSIONS

This meta-analysis is consistent with a lower risk of heart failure with intake of marine omega-3 fatty acids. These observational findings should be confirmed in a large randomized trial.

Association between circulating levels of IGF-1 and IGFBP-3 and lung cancer risk: a meta-analysis

Background

The insulin-like growth factor (IGF) system was documented to play a predominant role in neoplasia. As lung cancer is one of the most malignant cancers, we conducted a meta-analysis in order to investigate the strength of association between circulating IGF-1 and IGFBP-3 levels and lung cancer.

Methodology/Principal Findings

A systematic literature search was conducted to identify all prospective case-control studies and case-control studies on circulating IGFs and IGFBPs levels. Six nested case-control studies (1 043 case subjects and 11 472 control participants) and eight case-control studies (401 case subjects and 343 control participants) were included in this meta-analysis. Pooled measure was calculated as the inverse variance-weighted mean of the natural logarithm of multivariate adjusted OR with 95% CIs for highest vs. lowest levels to assess the association of circulating IGF-1 and IGFBP-3 concentrations and lung cancer. Standard mean difference (SMD) was also calculated to indicate the difference of the circulating IGF-1 and IGFBP-3 concentrations between the lung cancer case group and the control group. Of the nested case-control studies, ORs for the highest vs. lowest levels of IGF-1 and IGFBP-3 were 1.047 (95% CI: [0.802,1.367], P = 0.736) and 0.960 (95%CI: [0.591,1.559], P = 0.868) respectively; and SMDs were −0.079 (95%CI:[ −0.169, 0.011], P = 0.086) and −0.097 (95%CI:[ −0.264,0.071], P = 0.258) for IGF-1 and IGFBP-3 respectively. As to the case-control studies, SMDs were 0.568 (95%CI:[ −0.035, 1.171], P = 0.065) and −0.780 (95%CI:[ −1.358, −0.201], P = 0.008) for IGF-1 and IGFBP-3 respectively.

Conclusions/Significance

Inverse association was shown between IGFBP-3 and lung cancer in the case-control studies,and the circulating level of IGFBP-3 underwent a decline during tumorogenesis and development of lung cancer, which suggested IGFBP-3 a promising candidate for the biomarker of lung cancer.

Apolipoprotein E gene polymorphism in psoriasis: a meta-analysis

BACKGROUND AND AIMS

Several studies have shown that the apolipoprotein E (ApoE) gene is associated with the development of psoriasis. However, there is a controversy. The aim of the present study was to evaluate the association of psoriasis risk with ApoE polymorphisms.

METHODS

We carried out a systematic search of studies that explored associations between ApoE polymorphisms and psoriasis. The genotype distribution of the control group in each study was calculated to determine whether or not there was compliance with the Hardy-Weinberg equilibrium. Overall effect sizes were assessed by odds ratio (OR) with 95% confidence intervals (CI). The selection to use the random-effects model or fixed-effects model depended on the size of the heterogeneity among the included studies. The fail-safe number (Nfs) was used to test the potential publication bias. We analyzed the data using Stata v.10.0.

RESULTS

A total of seven studies with 966 patients and 1,086 controls were included. The results indicated that the ε2 allele was associated with increased risk of psoriasis (ε2 vs. ε3+ε4: OR = 1.47, 95% CI = 1.23-1.75, p <0.05), whereas the ε3 allele and ε3/ε3 genotype may decrease risk of psoriasis (OR = 0.71, 95% CI = 0.62-0.82, p <0.05; OR = 0.63, 95% CI = 0.52-0.77, p <0.05, respectively). In the subgroup analysis according to ethnicity, the increased risk of psoriasis remained in the Asian and European populations, whereas no significant association was found in other populations for other polymorphisms.

CONCLUSIONS

Our study suggests that the ApoE polymorphisms are associated with the risk of psoriasis, especially ε2 and ε3 alleles. Further studies are needed to confirm our results.

Association of fish and n-3 fatty acid intake with the risk of type 2 diabetes: a meta-analysis of prospective studies

Results from observational studies on the association of fish and n-3 fatty acid consumption with type 2 diabetes mellitus (T2DM) risk are conflicting. Hence, a meta-analysis was performed to investigate this association from cohort studies. A comprehensive search was then conducted to identify cohort studies on the association of fish and/or n-3 fatty acid intake with T2DM risk. In the highest v. lowest categorical analyses, the fixed or random-effect model was selected based on the homogeneity test among studies. Linear and non-linear dose-response relationships were also assessed by univariate and bivariate random-effect meta-regression with restricted maximum likelihood estimation. In the highest v. lowest categorical analyses, the pooled relative risk (RR) of T2DM for intake of fish and n-3 fatty acid was 1·146 (95 % CI 0·975, 1·346) and 1·076 (95 % CI 0·955, 1·213), respectively. In the linear dose-response relationship, the pooled RR for an increment of one time (about 105 g)/week of fish intake (four times/month) and of 0·1 g/d of n-3 fatty acid intake was 1·042 (95 % CI 1·026, 1·058) and 1·057 (95 % CI 1·042, 1·073), respectively. The significant non-linear dose-response associations of fish and n-3 fatty acid intake with T2DM risk were not observed. The present evidence from observational studies suggests that the intake of both fish and n-3 fatty acids might be weakly positively associated with the T2DM risk. Further studies are needed to confirm these results.

Folate Intake, MTHFR Polymorphisms, and the Risk of Colorectal Cancer: A Systematic Review and Meta-Analysis

Background. The objective was to determine whether relationships exist between the methylene-tetrahydrofolate reductase (MTHFR) polymorphisms and risk of colorectal cancer (CRC) and examine whether the risk is modified by level of folate intake. Methods. MEDLINE, Embase, and SCOPUS were searched to May 2012 using the terms "folic acid," "folate," "colorectal cancer," "methylenetetrahydrofolate reductase," "MTHFR." Observational studies were included which (1) assessed the risk of CRC for each polymorphism and/or (2) had defined levels of folate intake for each polymorphism and assessed the risk of CRC. Results. From 910 references, 67 studies met our criteria; hand searching yielded 10 studies. The summary risk estimate comparing the 677CT versus CC genotype was 1.02 (95% CI 0.95-1.10) and for 677TT versus CC was 0.88 (95% CI 0.80-0.96) both with heterogeneity. The summary risk estimates for A1298C polymorphisms suggested no reduced risk. The summary risk estimate for high versus low total folate for the 677CC genotype was 0.70 (95% CI 0.56-0.89) and the 677TT genotype 0.63 (95% CI 0.41-0.97). Conclusion. These results suggest that the 677TT genotype is associated with a reduced risk of developing CRC, under conditions of high total folate intake, and this associated risk remains reduced for both MTHFR 677 CC and TT genotypes.

Association of G894T polymorphism in endothelial nitric oxide synthase gene with the risk of ischemic stroke: A meta-analysis

Findings of a previous meta-analysis demonstrated no association between G894T polymorphism in endothelial nitric oxide synthase (eNOS) gene and ischemic stroke. Results of other studies have also been inconsistent. Updated meta-analysis was performed to assess the association between the eNOS gene G894T (rs1799983) polymorphism and the risk of ischemic stroke. Pooled odds ratios (ORs) with 95% confidence intervals (CIs) from fixed and random effects models were calculated. Heterogeneity in the studies was evaluated using the I². Meta-regression and the 'leave-one-out' sensitive analysis were used to examine the potential sources of between-study heterogeneity. Publication bias was estimated using the Egger's test. Data were available for 6,607 cases and 6,947 controls from 22 studies. Studies deviating from the Hardy-Weinberg equilibrium (HWE) in the controls and the key contributors to between-study heterogeneity were excluded. Significant associations between eNOS gene G894T polymorphism and the risk of ischemic stroke were observed in the dominant (OR 1.249; 95% CI, 1.145-1.361), the recessive (OR 1.255; 95% CI, 1.082-1.456) and the codominant models (OR 1.195; 95% CI, 1.115-1.281). Moreover, in the subgroup analysis based on the region (Asia and Europe), significant associations were observed between the dominant and codominant genetic models but not in the recessive model. The results of our meta-analysis suggested that eNOS gene G894T polymorphism was associated with the increased risk of ischemic stroke, and that the T allele may be an important risk factor for ischemic stroke. However, further studies are required to confirm this result.

Effects of care pathways on the in-hospital treatment of heart failure: a systematic review

BACKGROUND

Care pathways have become a popular tool to enhance the quality of care by improving patient outcomes, promoting patient safety, increasing patient satisfaction, and optimizing the use of resources. We performed a disease specific systematic review to determine how care pathways in the hospital treatment of heart failure affect in-hospital mortality, length of in-hospital stay, readmission rate and hospitalisation cost when compared with standard care.

METHODS

Medline, Cinahl, Embase and the Cochrane Central Register of Controlled Trials were searched from 1985 to 2010. Each study was assessed independently by two reviewers. Methodological quality of the included studies was assed using the Jadad methodological approach for randomised controlled trials, controlled clinical trials and the New Castle Ottawa Scale for case-control studies, cohort studies and time interrupted series.

RESULTS

Seven studies met the study inclusion criteria and were included in the systematic review with a total sample of 3,690 patients. The combined overall results showed that care pathways have a significant positive effect on mortality and readmission rate. A shorter length of hospital stay was also observed compared with the standard care group. No significant difference was found in the hospitalisation costs. More positive results were observed in controlled trials compared to randomized controlled trials.

CONCLUSION

By combining all possible results, it can be concluded that care pathways for treatment of heart failure decrease mortality rates and length of hospital stay, but no statistically significant difference was observed in the readmission rates and hospitalisation costs. However, one should be cautious with overall conclusions: what works for one organization may not work for another because of the subtle differences in processes and bottlenecks.

A dose-response meta-analysis of coffee consumption and bladder cancer

BACKGROUND

A number of studies have examined the association between coffee consumption and risk of bladder cancer, but uncertainty about the dose-response relationship remains.

MATERIALS AND METHODS

A comprehensive search was performed to identify all observational studies providing quantitative estimates between bladder cancer risk and coffee consumption. Dose-response relationship was assessed by restricted cubic spline model and bivariate random-effect meta-regression.

RESULTS

23 case-control studies with 7690 cases and 13,507 controls, and 5 cohort studies with 700 cases and 229,099 participants, met the inclusion criteria. Compared with non-drinkers and for case-control studies, the pooled smoking-adjusted RRs(95% CI) of bladder cancer were 1.07(1.02-1.13) for 1 cup/day, 1.15(1.05-1.26) for 2 cups/day, 1.22(1.08-1.38) for 3 cups/day, and 1.29(1.12-1.48) for 4 cups/day. For cohort studies, the pooled smoking-adjusted RRs of bladder cancer were 1.09(95% CI, 0.89-1.34) for 1 cup/day, 1.13(95% CI, 0.82-1.55) for 2 cups/day, 1.09(95% CI, 0.77-1.56) for 3 cups/day, and 1.01(95% CI, 0.69-1.48) for 4 cups/day.

CONCLUSIONS

Although data from case-control studies suggested that coffee was a risk factor for bladder cancer, there was no conclusive evidence on this association because of inconsistencies between case-control and cohort studies.

Severe mental illness in 33,588 prisoners worldwide: systematic review and meta-regression analysis

BACKGROUND

High levels of psychiatric morbidity in prisoners have been documented in many countries, but it is not known whether rates of mental illness have been increasing over time or whether the prevalence differs between low-middle-income countries compared with high-income ones.

AIMS

To systematically review prevalence studies for psychotic illness and major depression in prisoners, provide summary estimates and investigate sources of heterogeneity between studies using meta-regression.

METHOD

Studies from 1966 to 2010 were identified using ten bibliographic indexes and reference lists. Inclusion criteria were unselected prison samples and that clinical examination or semi-structured instruments were used to make DSM or ICD diagnoses of the relevant disorders.

RESULTS

We identified 109 samples including 33 588 prisoners in 24 countries. Data were meta-analysed using random-effects models, and we found a pooled prevalence of psychosis of 3.6% (95% CI 3.1-4.2) in male prisoners and 3.9% (95% CI 2.7-5.0) in female prisoners. There were high levels of heterogeneity, some of which was explained by studies in low-middle-income countries reporting higher prevalences of psychosis (5.5%, 95% CI 4.2-6.8; P = 0.035 on meta-regression). The pooled prevalence of major depression was 10.2% (95% CI 8.8-11.7) in male prisoners and 14.1% (95% CI 10.2-18.1) in female prisoners. The prevalence of these disorders did not appear to be increasing over time, apart from depression in the USA (P = 0.008).

CONCLUSIONS

High levels of psychiatric morbidity are consistently reported in prisoners from many countries over four decades. Further research is needed to confirm whether higher rates of mental illness are found in low- and middle-income nations, and examine trends over time within nations with large prison populations.

Nitric oxide synthase 3 (NOS3) 4b/a, T-786C and G894T polymorphisms in association with diabetic retinopathy susceptibility: a meta-analysis

AIMS

To assess the association between the NOS3 4b/a, T-786C and G894T polymorphisms and diabetic retinopathy (DR) susceptibility.

MATERIALS AND METHODS

Twenty-one studies covering 8,111 subjects were included. The fixed or random effect model used was based on heterogeneity.

RESULTS

A significant association of the intron 4a allele in the NOS3 4b/a polymorphism with reduced risk of DR was found in dominant (OR 0.778, 95% CI 0.654-0.926) and additive (OR 0.809, 95% CI 0.698-0.937) models. Subgroup analysis revealed that the intron 4a allele additive model (OR 0.807, 95% CI 0.697-0.935) was associated with DR risk in type 2 diabetic patients. We also found a marginally significant association of the C allele in the T-786C polymorphism with reduced risk of proliferative DR. In contrast, no statistically significant association was observed between the G894T polymorphism and DR risk, either in the overall or subgroup analyses.

CONCLUSIONS

The intron 4a allele of the 4b/a polymorphism in the eNOS gene has protective effects against DR, especially in type 2 diabetic patients. The C allele of the T-786C polymorphism may be a protective factor for proliferative DR. However, the G894T polymorphism does not appear to influence the development of DR. This conclusion warrants confirmation by further studies.

Association between IL6 -174G/C and cancer: A meta-analysis of 105,482 individuals

Interleukin-6 (IL6) is a pleiotropic inflammatory cytokine, which is implicated in the development and progression of several types of cancer. The -174G/C polymorphism of the IL6 gene controls serum levels of IL6 and may be associated with cancer risk, but the results from the published studies on the association between this polymorphism and cancer risk are conflicting. A comprehensive meta-analysis was conducted to assess the association of IL6 -174G/C with cancer risk. Studies were identified by searches of MEDLINE and HuGE Published Literature databases, with no restrictions. An eligible 83 articles involving 44,735 cancer patients and 60,747 controls were included. Combined odds ratios (ORs) and 95% confidence intervals (CIs) were used to assess the strength of the association between the IL6 -174 G/C polymorphism and cancer risk. Potential sources of heterogeneity were explored by meta-regression and sensitivity analysis. Overall, the IL6 -174G/C polymorphism was not significantly associated with cancer risk. However, cancer risk was increased for individuals with the CC genotype compared to those carrying the GG genotype in African populations (OR=1.83, 95% CI 1.26-2.67, P=0.002), but not in Caucasian populations (OR=1.00, 95% CI 0.92-1.08, P=0.938). The present meta-analysis provides the first evidence of the ethnic-specific association of the IL6 -174G/C polymorphism with cancer risk. Further investigations with a large number of cases and controls are required to confirm the associations between this polymorphism and cancer in Africans.

Aerosol generating procedures and risk of transmission of acute respiratory infections to healthcare workers: a systematic review

Aerosol generating procedures (AGPs) may expose health care workers (HCWs) to pathogens causing acute respiratory infections (ARIs), but the risk of transmission of ARIs from AGPs is not fully known. We sought to determine the clinical evidence for the risk of transmission of ARIs to HCWs caring for patients undergoing AGPs compared with the risk of transmission to HCWs caring for patients not undergoing AGPs. We searched PubMed, EMBASE, MEDLINE, CINAHL, the Cochrane Library, University of York CRD databases, EuroScan, LILACS, Indian Medlars, Index Medicus for SE Asia, international health technology agencies and the Internet in all languages for articles from 01/01/1990 to 22/10/2010. Independent reviewers screened abstracts using pre-defined criteria, obtained full-text articles, selected relevant studies, and abstracted data. Disagreements were resolved by consensus. The outcome of interest was risk of ARI transmission. The quality of evidence was rated using the GRADE system. We identified 5 case-control and 5 retrospective cohort studies which evaluated transmission of SARS to HCWs. Procedures reported to present an increased risk of transmission included [n; pooled OR(95%CI)] tracheal intubation [n = 4 cohort; 6.6 (2.3, 18.9), and n = 4 case-control; 6.6 (4.1, 10.6)], non-invasive ventilation [n = 2 cohort; OR 3.1(1.4, 6.8)], tracheotomy [n = 1 case-control; 4.2 (1.5, 11.5)] and manual ventilation before intubation [n = 1 cohort; OR 2.8 (1.3, 6.4)]. Other intubation associated procedures, endotracheal aspiration, suction of body fluids, bronchoscopy, nebulizer treatment, administration of O2, high flow O2, manipulation of O2 mask or BiPAP mask, defibrillation, chest compressions, insertion of nasogastric tube, and collection of sputum were not significant. Our findings suggest that some procedures potentially capable of generating aerosols have been associated with increased risk of SARS transmission to HCWs or were a risk factor for transmission, with the most consistent association across multiple studies identified with tracheal intubation.

Association of C47T polymorphism in SOD2 gene with coronary artery disease: a case-control study and a meta-analysis

Oxidative damage promotes atherosclerosis. SOD2 is an important antioxidant enzyme. A case-control study and a meta-analysis were performed to assess the association of C47T polymorphism in SOD2 gene with premature, late-onset and overall coronary artery disease (CAD) risk. A hospital-based case-control study was conducted with 269 premature CAD cases, 278 late-onset CAD cases and 299 healthy controls. Polymerase chain reaction (PCR) and Pyrosequencing were used to detect the polymorphism. Multinomial logistic regression model was performed to estimate odds ratio (OR) with 95% confidence intervals (CIs) and adjust potential confounders. A meta-analysis was performed using eight outcomes including our result. Fixed or random effect pooled measure was selected on the basis of homogeneity test among studies. Heterogeneity among studies was evaluated using I (2). Meta-regression was used to explore potential sources of between-study heterogeneity. Publication bias was estimated using Peters's linear regression test. In our case-control study, compared with the TT as the reference, the mutant genotype of CC + TC was significantly associated with a reduced premature CAD risk both in univariate (OR = 0.60, 95% CI = 0.41-0.87) and multivariate (OR = 0.59, 95% CI = 0.40-0.87) logistic regressions, but not with late-onset CAD risk. After excluding one article that deviated from Hardy-Weinberg equilibrium in controls, this meta-analysis showed a significant association of the C allele with reduced risk of CAD in dominant (FEM: OR = 0.69, 95% CI = 0.61-0.78), recessive (OR = 0.64, 95% CI = 0.50-0.82), and codominant (FEM: OR = 0.73, 95% CI = 0.65-0.80) models. Our study suggested that the mutant genotype of CC + TC was significantly associated with a reduced CAD risk.

UCP2 -866G/A and Ala55Val, and UCP3 -55C/T polymorphisms in association with type 2 diabetes susceptibility: a meta-analysis study

AIMS/HYPOTHESIS

A meta-analysis was performed to assess the association between the UCP2 -866G/A, UCP2 Ala55Val and UCP3 -55C/T polymorphisms and type 2 diabetes susceptibility.

METHODS

A literature-based search was conducted to identify all relevant studies. The fixed or random effect pooled measure was calculated mainly at the allele level to determine heterogeneity bias among studies. Further analyses were performed that stratified for ethnicity.

RESULTS

We examined 17 publications. Stratified analysis for ethnicity and sensitivity analysis revealed that there was no heterogeneity between studies for these variants. Using an additive model, no significant association of the UCP2 -866G/A polymorphism with type 2 diabetes risk was observed, either in participants of Asian (OR 1.05, 95% CI 0.96, 1.16) or of European (OR 1.03, 95% CI 0.99, 1.07) descent. Neither the UCP2 Ala55Val nor the UCP3 -55C/T polymorphism showed any significant association with type 2 diabetes risk in Europeans (OR 1.04, 95% CI 0.98, 1.09 for Ala55Val; OR 1.04, 95% CI 1.00, 1.09 for -55C/T). In contrast, a statistically significant association was observed for both polymorphisms in participants of Asian descent (OR 1.23, 95% CI 1.12, 1.36 for Ala55Val; OR 1.15, 95% CI 1.03, 1.28 for -55C/T).

CONCLUSIONS/INTERPRETATION

Our meta-analysis suggests that the UCP2 -866G/A polymorphism is unlikely to be associated with increased type 2 diabetes risk in the populations investigated. In contrast, our results indicate that the UCP2 Ala55Val and UCP3 -55C/T polymorphisms may indeed be risk factors for susceptibility to type 2 diabetes in individuals of Asian descent, but not in individuals of European descent. This conclusion warrants confirmation by further studies.

Impact of CYP2C19 variant genotypes on clinical efficacy of antiplatelet treatment with clopidogrel: systematic review and meta-analysis

OBJECTIVE

To evaluate the accumulated information from genetic association studies investigating the impact of variants of the cytochrome P450 (CYP) 2C19 genotype on the clinical efficacy of clopidogrel.

DESIGN

Systematic review and meta-analysis with a structured search algorithm and prespecified eligibility criteria for retrieval of relevant studies; dominant genetic model assumptions and quantitative methods for calculating summary effect estimates from study level odds ratios; systematic assessment of bias within and between studies; and grading of the cumulative evidence by consensus criteria.

DATA SOURCES

Medline, Embase, the Cochrane Library, online databases, contents pages and bibliographies of general medical, cardiovascular, pharmacological, and genetic journals. Eligibility criteria for selecting studies Original full length reports assessing the cumulative incidence of major adverse cardiovascular events or stent thrombosis over a follow-up period of at least a month in association with carrier status for the loss of function or gain of function CYP2C19 allele in adult patients with coronary artery disease and a clinical presentation of acute coronary syndrome or stable angina pectoris who were taking clopidogrel.

RESULTS

15 studies met the inclusion criteria. The random effects summary odds ratio for stent thrombosis in carriers of at least one CYP2C19 loss of function allele versus non-carriers combining nine studies was 1.77 (95% confidence interval 1.31 to 2.40; P < 0.001). This nominally significant odds ratio was subject to considerable bias across the studies (small study effect bias and replication diversity). The adjustment for these quality modifiers tended to abolish the association. The corresponding random effects summary odds ratio of major adverse cardiovascular events for 12 studies combined was 1.11 (0.89 to 1.39; P = 0.36). The random effects summary odds ratio of stent thrombosis in carriers versus non-carriers of at least one CYP2C19*17 gain of function allele for three studies combined was 0.99 (0.60 to 1.62; P = 0.96), and the corresponding odds ratio of major adverse cardiovascular events in five studies was 0.93 (0.75 to 1.14; P = 0.48). The overall quality of epidemiological evidence was graded as low, which excludes reliable clinical assessments.

CONCLUSIONS

Accumulated information from genetic association studies does not indicate a substantial or consistent influence of CYP2C19 gene polymorphisms on the clinical efficacy of clopidogrel. The current evidence does not support the use of individualised antiplatelet regimens guided by CYP2C19 genotype.

Association of CD14 -260 (-159) C>T and asthma: a systematic review and meta-analysis

Background

Asthma is a phenotypically diverse disease with genetic susceptibility. A single nucleotide polymorphism (SNP) in the CD14 gene at position -260 (also known as -159) C>T has been inconsistently associated with asthma. The aim of this study was to estimate the combined likelihood of developing asthma given the CD14 -260C>T genotype.

Methods

Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, a systematic search and meta-analysis of the literature was conducted to estimate the association between this SNP and asthma. Planned subgroup analyses were performed to detect potential sources of heterogeneity from selected study characteristics. Post-hoc sensitivity analysis was performed to identify studies exerting excessive influence on among-study heterogeneity and combined effects.

Results

Meta-analysis of 23 studies yielded a non-significant overall association with high heterogeneity across studies. After restricting analysis to studies using atopic asthma and non-atopic non-asthma case-control phenotypes and excluding studies influencing heterogeneity, the genotype-specific odds ratios (ORs) suggested a codominant model. Carriers of the TT and CT genotypes were about 33% less likely (OR = 0.67, 95% CI: 0.54-0.84) and about 20% less likely (OR = 0.80, 95% CI: 0.66-0.95), respectively, to have atopic asthma compared to carriers of the CC genotype. Among-study heterogeneity may be explained by overly broad asthma phenotype definitions, gene-environment interactions, and gene-gene interactions.

Conclusions

A protective dose-response relationship between the CD14 -260T allele and atopic asthma susceptibility was observed. These results demonstrate the importance of precisely specified case-control groups as well as the need to assess interactions in the investigation of complex diseases such as asthma.

Meta-analysis of homogeneous subgroups reveals association between PDE4D gene variants and ischemic stroke

BACKGROUND

An Icelandic study showed a significant positive association between phosphodiesterase 4D (PDE4D) gene variants and stroke. However, subsequent studies reported conflicting results, possibly due to small sample sizes and the heterogeneity of the studies.

METHOD

We performed a meta-analysis on 6 SNPs of the PDE4D gene to investigate the association between this gene and ischemic stroke by integrating the results of previous studies, comprising 11,834 cases and 15,233 controls. A pooled genotypic odds ratio (OR) for each SNP was determined under 3 genetic models (i.e. dominant, recessive, and codominant) using both fixed- and random-effects models with consideration for heterogeneity and publication bias across studies.

RESULTS

Among the SNPs included in this study, SNP56 (rs702553) showed the most significant association with ischemic stroke in a meta-analysis comprised of 7 homogenous studies. The overall OR of the TT genotype compared to the AA genotype was 1.29 (95% CI 1.03-1.61; p = 0.022). For SNP83 (rs966221), a protective effect of the ancestral allele T was observed only in Asian populations (ORTT 0.79, 95% CI 0.69-0.90; p = 0.0005). This meta-analysis revealed a significant association of PDE4D gene variants with the risk of ischemic stroke, and further investigations are warranted to evaluate possible ethnic-specific effects.