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Publication Bias (publication + bias)
Selected AbstractsThe effect of thiazolidinediones on adiponectin serum level: a meta-analysisDIABETES OBESITY & METABOLISM, Issue 5 2008N. Riera-Guardia Background and aims:, Adiponectin is a hormone mainly produced by white adipose tissue. Decreased levels of adiponectin are linked with visceral obesity, insulin resistance states, and cardiovascular diseases. Recently, several studies have pointed out an increase in adiponectin serum levels in subjects undergoing treatment with thiazolidinediones (TZD). The aim of this study is to systematically review the current state of evidence of the effect of TZD on adiponectin serum level with special attention to avoid publication bias. Materials and methods:, An extensive literature search was performed. Meta Analysis Version 2.0 computer program was used to calculate statistical differences in means and 95% confidence interval (CI). Publication bias was assessed using different statistical approaches. Results:, In the meta-analysis including 19 studies the overall standardized mean difference was 0.94 (95% CI, 0.81,1.06) which means that subjects treated with TZDs on average had means of adiponectin concentration that were about 1 standard deviation higher than the comparison groups even after controlling for possible biases. Conclusions:, The results obtained agree with a moderate increase of serum adiponectin. The results clearly reveal an increase of endogenous serum adiponectin levels by intake of TZDs and may point to a potential new option to manage obesity-related diseases. [source] The causes, consequences and detection of publication bias in psychiatryACTA PSYCHIATRICA SCANDINAVICA, Issue 4 2000Simon M. Gilbody Objective: Publication bias threatens the validity of published research, although this topic has received little attention in psychiatry. The purpose of this article is to produce a systematic overview of the causes and consequences of publication bias and to summarize the available methods with which it is detected and corrected. Method: Empirical evidence for the existence of publication bias is reviewed and the following methods are applied to an illustrative case example from psychiatry: funnel plot analysis; the ,file drawer method'; linear regression techniques; rank correlation; ,trim and fill'. Results: Small studies are particularly susceptible to publication and related bias. All methods to detect publication bias depend upon the availability of a number of individual studies with a range of sample sizes. Unfortunately, large numbers of studies of varying sample size are not always available in many areas of psychiatric research. Conclusion: Where possible researchers should always test for the presence of publication bias. The problem of publication bias will not be solved by anything other than a prospective trials register. [source] Publication bias: a concern just for drug prevention or for the entire drug control literature?DRUG AND ALCOHOL REVIEW, Issue 4 2008Jonathan P. Caulkins No abstract is available for this article. [source] Publication bias perpetuates use of ineffective drugs in strokeINTERNATIONAL JOURNAL OF STROKE, Issue 3 2009K. Prasad Drugs approved and used for treatment of stroke vary from country to country. This is, at least, partly because of variation in the standards of evidence that is required for approval of drugs across countries. For example, some countries, usually low and middle income ones, approve a drug on the basis of a small positive study or post hoc subgroup analysis in a overall negative study, while others, usually high income countries, require confirmatory or replication studies before approving the same drug. Needless to say that such confirmatory or replication studies need to be published and adequately disseminated as soon as possible so that approval decisions can be revised in the light of additional evidence. However, this does not always happen. The new evidence often remains hidden in the form of nonpublication or abbreviated publication. Sometimes, it is published but with undue delay. What is worrisome is that these problems occur more often when the new evidence does not favor the new drugs than when it favors them, a manifestation of what is called ,publication bias.' This bias is well documented in the stroke research literature (1, 2). [source] Publication bias in ecology and evolution: an empirical assessment using the ,trim and fill' methodBIOLOGICAL REVIEWS, Issue 2 2002MICHAEL D. JENNIONS ABSTRACT Recent reviews of specific topics, such as the relationship between male attractiveness to females and fluctuating asymmetry or attractiveness and the expression of secondary sexual characters, suggest that publication bias might be a problem in ecology and evolution. In these cases, there is a significant negative correlation between the sample size of published studies and the magnitude or strength of the research findings (formally the ,effect size'). If all studies that are conducted are equally likely to be published, irrespective of their findings, there should not be a directional relationship between effect size and sample size; only a decrease in the variance in effect size as sample size increases due to a reduction in sampling error. One interpretation of these reports of negative correlations is that studies with small sample sizes and weaker findings (smaller effect sizes) are less likely to be published. If the biological literature is systematically biased this could undermine the attempts of reviewers to summarise actual biology relationships by inflating estimates of average effect sizes. But how common is this problem? And does it really effect the general conclusions of literature reviews? Here, we examine data sets of effect sizes extracted from 40 peer-reviewed, published meta-analyses. We estimate how many studies are missing using the newly developed ,trim and fill' method. This method uses asymmetry in plots of effect size against sample size (,funnel plots') to detect ,missing' studies. For random-effect models of meta-analysis 38% (15/40) of data sets had a significant number of ,missing' studies. After correcting for potential publication bias, 21% (8/38) of weighted mean effects were no longer significantly greater than zero, and 15% (5/34) were no longer statistically robust when we used random-effects models in a weighted meta-analysis. The mean correlation between sample size and the magnitude of standardised effect size was also significantly negative (rs=-0.20, P < 0-0001). Individual correlations were significantly negative (P < 0.10) in 35% (14/40) of cases. Publication bias may therefore effect the main conclusions of at least 15,21% of meta-analyses. We suggest that future literature reviews assess the robustness of their main conclusions by correcting for potential publication bias using the ,trim and fill' method. [source] Augmentation of clozapine with a second antipsychotic , a meta-analysis of randomized, placebo-controlled studiesACTA PSYCHIATRICA SCANDINAVICA, Issue 6 2009D. M. Taylor Objective:, Inadequate response to clozapine treatment is frequently encountered in practice and augmentation strategies have been developed in an attempt to improve response. Aims of the study were to evaluate the therapeutic effect of adding an antipsychotic drug to clozapine treatment. Method:, Meta-analysis of randomized, placebo-controlled studies of antipsychotic augmentation of clozapine treatment. Results:, Ten studies (including 522 subjects) met inclusion criteria. Antipsychotic augmentation showed significant benefit over the addition of placebo on only one outcome measure examined [mean effect size for rating scale score (BPRS/PANSS) ,0.180, 95% CI ,0.356 to ,0.004]. Antipsychotic augmentation showed no advantage on withdrawals from trials (risk ratio 1.261, 95% CI 0.679,2.345) or on CGI scores (effect size ,0.661, 95% CI ,1.475 to 0.151). Duration of study was not associated with outcome (P = 0.95). There was no evidence of publication bias. Conclusion:, In studies lasting up to 16 weeks, the addition of an antipsychotic to clozapine treatment has marginal therapeutic benefit. Longer and larger trials are necessary to demonstrate the precise therapeutic utility of antipsychotic co-therapy with clozapine. [source] How to read and understand and use systematic reviews and meta-analysesACTA PSYCHIATRICA SCANDINAVICA, Issue 6 2009S. Leucht Objective,: Systematic reviews and meta-analyses are increasingly frequently used in the evaluation of medical treatments. This review explains the principles of the methodology, significance and limitations of systematic reviews. Method:, Short review article. Results:, In contrast to conventional reviews, systematic reviews use a structured approach in retrieving, analyzing and interpreting the evidence. A comprehensive search strategy is applied to identify all relevant trials. Study selection and data extraction is performed independently by at least two reviewers. The data are usually synthesized in a meta-analysis applying statistical methods to examine homogeneity. Funnel plots and other statistical methods are applied to detect publication bias. Conclusion:, Due to the enormous amount of scientific information published every year, systematic reviews and meta-analyses have become indispensable methods for the evaluation of medical treatments. [source] ,Stockholm syndrome': psychiatric diagnosis or urban myth?ACTA PSYCHIATRICA SCANDINAVICA, Issue 1 2008M. Namnyak Objective:, ,Stockholm syndrome' is a term used to describe the positive bond some kidnap victims develop with their captor. High-profile cases are reported by the media although the diagnosis is not described in any international classification system. Here we review the evidence base on ,Stockholm syndrome'. Method:, Databases (PubMED, EMBASE, PsycINFO, CINAHL) were systematically searched. We compared features of cases widely reported in the English language media to identify common themes which may form a recognizable syndrome. Results:, We identified 12 papers that met inclusion criteria. The existing literature consists mostly of case reports; furthermore there is ambiguity in the use of the term. No validated diagnostic criteria have been described. Four common features were found between the five cases studied. Conclusion:, There is little published academic research on ,Stockholm syndrome' although study of media reports reveals similarities between well publicized cases. This may be due to reporting and publication bias. [source] Psychotherapy for depression among children and adolescents: a systematic reviewACTA PSYCHIATRICA SCANDINAVICA, Issue 2 2007N. Watanabe Objective:, To examine the clinical benefit, the harm and the cost-effectiveness of psychotherapies in comparison with no treatment, waiting-list controls, attention-placebos, and treatment as usual in depressed youths. Method:, Meta-analyses were undertaken by using data from all relevant randomized-controlled trials identified by a comprehensive literature search. The primary outcome was relative risk (RR) of response. Results:, We identified 27 studies containing 35 comparisons and 1744 participants. At post-treatment, psychotherapy was significantly superior (RR = 1.39, 95% CI 1.18,1.65, P = 0.0001, number-needed to treat 4.3). There was an evidence of the existence of small study effects, including a publication bias (P < 0.001). The superiority of psychotherapy was no longer statistically significant (1.18 [0.94,1.47], P = 0.15) at 6-month follow-up. None of the studies reported adverse effects or cost-effectiveness outcomes. Conclusion:, Although the findings were biased by some small positive trials, psychotherapies appear to help depressed youths for the short term, but are no longer significantly favourable at 6-month follow-up. [source] The effect of thiazolidinediones on adiponectin serum level: a meta-analysisDIABETES OBESITY & METABOLISM, Issue 5 2008N. Riera-Guardia Background and aims:, Adiponectin is a hormone mainly produced by white adipose tissue. Decreased levels of adiponectin are linked with visceral obesity, insulin resistance states, and cardiovascular diseases. Recently, several studies have pointed out an increase in adiponectin serum levels in subjects undergoing treatment with thiazolidinediones (TZD). The aim of this study is to systematically review the current state of evidence of the effect of TZD on adiponectin serum level with special attention to avoid publication bias. Materials and methods:, An extensive literature search was performed. Meta Analysis Version 2.0 computer program was used to calculate statistical differences in means and 95% confidence interval (CI). Publication bias was assessed using different statistical approaches. Results:, In the meta-analysis including 19 studies the overall standardized mean difference was 0.94 (95% CI, 0.81,1.06) which means that subjects treated with TZDs on average had means of adiponectin concentration that were about 1 standard deviation higher than the comparison groups even after controlling for possible biases. Conclusions:, The results obtained agree with a moderate increase of serum adiponectin. The results clearly reveal an increase of endogenous serum adiponectin levels by intake of TZDs and may point to a potential new option to manage obesity-related diseases. [source] Common variants in the ATP-sensitive K+ channel genes KCNJ11 (Kir6.2) and ABCC8 (SUR1) in relation to glucose intolerance: population-based studies and meta-analyses,DIABETIC MEDICINE, Issue 5 2005R. M. Van Dam Abstract Aims To evaluate the relation between common variants in the ATP-sensitive K+ channel genes and glucose intolerance. Methods We conducted a meta-analysis of reported association studies in Caucasian populations for common variants in the ABCC8 (exons 16 and 18) and the KCNJ11 (E23K) gene and examined sources of heterogeneity in the results. The meta-analysis was based on 7768,10216 subjects (depending on the gene variant), and included two new population-based studies in the Netherlands with 725 cases and 742 controls. Results For the KCNJ11 variant, the summary odds ratio (OR) for glucose intolerance was 1.12 (1.01,1.23, P = 0.03) for the EK genotype and 1.44 (1.17,1.78, P = 0.0007) for the KK genotype, as compared with the EE genotype. For the ABCC8 exon 16 variant, the OR was 1.06 (0.94,1.19, P = 0.34) for ct and 0.93 (0.71,1.20, P = 0.56) for tt, as compared with the cc genotype. For ABCC8 exon 18, the OR was 1.20 (0.97,1.49, P = 0.10) for CT/TT, as compared with the CC genotype. Studies of the ABCC8 variants that were published first or had smaller sample sizes (for the exon 18 variant) showed stronger associations, which may indicate publication bias. For the ABCC8 exon 18 and the KCNJ11 variant, associations were stronger for studies of clinical diabetes than newly detected glucose intolerance. The population attributable risk for clinical Type 2 diabetes was 6.2% for the KCNJ11 KK genotype and 10.1% for the KCNJ11 EK and KK genotype combined. Conclusions The common KCNJ11 E23K gene variant, but not the ABCC8 exon 16 or exon 18 variant, was consistently associated with Type 2 diabetes. [source] Coxsackie B virus serology and Type 1 diabetes mellitus: a systematic review of published case-control studiesDIABETIC MEDICINE, Issue 6 2004J. Green Abstract Background Enteroviruses, in particular Coxsackie B4, have been implicated in the aetiology of Type 1 diabetes mellitus, but the epidemiological evidence has not been systematically evaluated. Methods Systematic review of evidence from published controlled studies of the relationship between Coxsackie B virus serology and incident or prevalent Type 1 diabetes mellitus. Studies were identified through a Medline search (1966 to 2002), supplemented by references from identified papers and hand search of relevant journals. All studies (full papers, abstracts or letters) with data adequate for calculation of unadjusted odds ratios (with 95% confidence intervals) for Type 1 diabetes mellitus in relation to Coxsackie B virus serology were included. Results The review included 26 case-control studies; no cohort study met the inclusion criteria. Odds ratios for Type 1 diabetes mellitus in serology-positive vs. serology-negative subjects ranged from 0.2 to 22.3. For Coxsackie B (any serotype) 7/13 studies had point estimates significantly greater than 1.0 (P < 0.05). For Coxsackie B3, Coxsackie B4 and Coxsackie B5-specific assays, 1/11, 6/17 and 1/11 studies, respectively, had point estimates significantly greater than 1.0. Summary odds ratios were not calculated because of doubts about the validity of individual study estimates, heterogeneity between studies, and the possibility of publication bias. Conclusions The results of these studies are inconsistent and do not provide convincing evidence for or against an association between Coxsackie B virus infection and Type 1 diabetes mellitus. Better designed studies using effective assays are needed to resolve this important issue. [source] The causes, consequences and detection of publication bias in psychiatryACTA PSYCHIATRICA SCANDINAVICA, Issue 4 2000Simon M. Gilbody Objective: Publication bias threatens the validity of published research, although this topic has received little attention in psychiatry. The purpose of this article is to produce a systematic overview of the causes and consequences of publication bias and to summarize the available methods with which it is detected and corrected. Method: Empirical evidence for the existence of publication bias is reviewed and the following methods are applied to an illustrative case example from psychiatry: funnel plot analysis; the ,file drawer method'; linear regression techniques; rank correlation; ,trim and fill'. Results: Small studies are particularly susceptible to publication and related bias. All methods to detect publication bias depend upon the availability of a number of individual studies with a range of sample sizes. Unfortunately, large numbers of studies of varying sample size are not always available in many areas of psychiatric research. Conclusion: Where possible researchers should always test for the presence of publication bias. The problem of publication bias will not be solved by anything other than a prospective trials register. [source] A case study of publication bias in an influential series of reviews of drug educationDRUG AND ALCOHOL REVIEW, Issue 5 2007JIM McCAMBRIDGE Abstract There has been remarkably little demonstration of the deleterious impact of publication bias within addiction science or indeed in wider healthcare policy and practice. An account is provided here of how publication bias was identified in relation to a series of drug education reviews which have been very influential on subsequent research, policy and practice. Later data analyses unpublished by the same review team demonstrated earlier findings to be unreliable. These later findings were not published. The policy context in which evidence on drug education in schools is produced is considered and the need for unbiased evidence is emphasised. A broadened conception of publication bias is proposed which takes account of the environment in which publication decision-making occurs. It is suggested that this is particularly necessary for subjects with such direct policy relevance as the effectiveness of drug education in schools. [source] Alcohol and hypertension: gender differences in dose,response relationships determined through systematic review and meta-analysisADDICTION, Issue 12 2009Benjamin Taylor ABSTRACT Aims To analyze the dose,response relationship between average daily alcohol consumption and the risk of hypertension via systematic review and meta-analysis. Design A computer-assisted search was completed for 10 databases, followed by hand searches of relevant articles. Only studies with longitudinal design, quantitative measurement of alcohol consumption and biological measurement of outcome were included. Dose,response relationships were assessed by determining the best-fitting model via first- and second-degree fractional polynomials. Various tests for heterogeneity and publication bias were conducted. Findings A total of 12 cohort studies were identified from the literature from the United States, Japan and Korea. A linear dose,response relationship with a relative risk of 1.57 at 50 g pure alcohol per day and 2.47 at 100 g per day was seen for men. Among women, the meta-analysis indicated a more modest protective effect than reported previously: a significant protective effect was reported for consumption at or below about 5 g per day, after which a linear dose,response relationship was found with a relative risk of 1.81 at 50 g per day and of 2.81 at an average daily consumption of 100 g pure alcohol per day. Among men, Asian populations had higher risks than non-Asian populations. Conclusions The risk for hypertension increases linearly with alcohol consumption, so limiting alcohol intake should be advised for both men and women. [source] Online support for smoking cessation: a systematic review of the literatureADDICTION, Issue 11 2009Lion Shahab ABSTRACT Aim To examine the efficacy and acceptability of online, interactive interventions for smoking cessation and to identify treatment effect moderators and mediators. Methods A systematic review and meta-analysis of the literature (1990,2008) was conducted, finding 11 relevant randomized controlled trials. Data were extracted and risk ratios and risk differences estimated with a random effects model. Results There was no evidence of publication bias. Included trials were of variable methodological quality. Web-based, tailored, interactive smoking cessation interventions were effective compared with untailored booklet or e-mail interventions [rate ratio (RR) 1.8; 95% confidence interval (CI) 1.4,2.3] increasing 6-month abstinence by 17% (95% CI 12,21%). No overall effect of interactive compared with static web-based interventions was detected but there was significant heterogeneity, with one study obtaining a clear effect and another failing to find one. Few moderating or mediating factors were evaluated in studies and those that were had little effect. Pooled results suggest that only interventions aimed at smokers motivated to quit were effective (RR 1.3, 95% CI 1.0,1.7). Fully automated interventions increased smoking cessation rates (RR 1.4, 95% CI 1.0,2.0), but evidence was less clear-cut for non-automated interventions. Overall, the web-based interventions evaluated were considered to be acceptable and user satisfaction was generally high. Conclusion Interactive, web-based interventions for smoking cessation can be effective in aiding cessation. More research is needed to evaluate the relative efficacy of interactive web-based interventions compared with static websites. [source] Meta-analysis of standardized incidence and mortality rates of childhood leukaemia in proximity to nuclear facilitiesEUROPEAN JOURNAL OF CANCER CARE, Issue 4 2007P.J. BAKER phd The meta-analysis combined and statistically analysed studies of childhood leukaemia and nuclear facilities. Focus was on studies that calculated standardized rates for individual facilities. Due to variability between study designs, eight separate analyses were performed stratified by age and zone. One hundred and thirty-six sites were used in at least one analysis. Unadjusted, fixed effects and random effects models were used. Meta-rates greater than one were found in all models at all stratification levels often achieving statistical significance. Caution must be used when interpreting these results. The meta-analysis was able to show an increase in childhood leukaemia near nuclear facilities, but does not support a hypothesis to explain the excess. Each type of model utilized has limitations. Fixed effects models give greater weight to larger studies; however, population density may be a risk factor. Random effects models give greater weight to smaller studies that may be more likely to be affected by publication bias. A limitation of the overall study design is that standardized rates must be available for individual sites which led to exclusion of studies that only calculated rates for multiple sites and those that presented other statistical methods. Further, dose-response studies do not support excess rates found near nuclear facilities. However, it cannot be ignored that the majority of studies have found elevated rates, although not usually statistically significant. [source] Thrombolysis in patients with acute ischemic stroke due to arterial extracranial dissectionEUROPEAN JOURNAL OF NEUROLOGY, Issue 5 2009M. D. I. Vergouwen Background and purpose:, No data of randomized controlled trials investigating the effect of thrombolysis in patients with ischemic stroke caused by an extracranial dissection are available. Previous case series suggested that thrombolysis in this group of patients is safe and improves outcome, however publication bias may play a role. The purpose of the present study was to describe outcome of consecutive patients with ischemic stroke caused by an extracranial dissection treated with recombinant tissue plasminogen activator (rtPA), derived from a well-defined ischemic stroke cohort. Methods:, All consecutive patients with a transient ischemic attack (TIA) or ischemic stroke admitted to the Academic Medical Center Amsterdam between January 1, 2007 and September 1, 2007 were prospectively registered. Cause of TIA/stroke, treatment, and 6-months outcome were recorded. Results:, During the study period 252 patients were evaluated with TIA or ischemic stroke. Eight patients (3%) had an extracranial dissection. Of the six rtPA treated patients, five had good clinical outcome and one patient died. The two patients who were not treated with rtPA, because of minor stroke, had good clinical outcome 6 months after index event. Discussion:, Treatment with rtPA seems to be safe and feasible in ischemic stroke patients with an extracranial dissection. [source] POWER AND POTENTIAL BIAS IN FIELD STUDIES OF NATURAL SELECTIONEVOLUTION, Issue 3 2004Erika I. Hersch Abstract The advent of multiple regression analyses of natural selection has facilitated estimates of both the direct and indirect effects of selection on many traits in numerous organisms. However, low power in selection studies has possibly led to a bias in our assessment of the levels of selection shaping natural populations. Using calculations and simulations based on the statistical properties of selection coefficients, we find that power to detect total selection (the selection differential) depends on sample size and the strength of selection relative to the opportunity of selection. The power of detecting direct selection (selection gradients) is more complicated and depends on the relationship between the correlation of each trait and fitness and the pattern of correlation among traits. In a review of 298 previously published selection differentials, we find that most studies have had insufficient power to detect reported levels of selection acting on traits and that, in general, the power of detecting weak levels of selection is low given current study designs. We also find that potential publication bias could explain the trend that reported levels of direct selection tend to decrease as study sizes increase, suggesting that current views of the strength of selection may be inaccurate and biased upward. We suggest that studies should be designed so that selection is analyzed on at least several hundred individuals, the total opportunity of selection be considered along with the pattern of selection on individual traits, and nonsignificant results be actively reported combined with an estimate of power. [source] Helicobacter pylori Infection and Colorectal Cancer Risk: A Meta-AnalysisHELICOBACTER, Issue 2 2006Natalia Zumkeller Abstract Background:, Several studies suggested an association between Helicobacter pylori infection and colorectal carcinoma or adenoma risk. However, different authors reported quite varying estimates. We carried out a systematic review and meta-analysis of published studies investigating this association and paid special attention to the possibility of publication bias and sources of heterogeneity between studies. Materials and Methods:, An extensive literature search and cross-referencing were performed to identify all published studies. Summary estimates were obtained using random-effects models. The presence of possible publication bias was assessed using different statistical approaches. Results:, In a meta-analysis of the 11 identified human studies, published between 1991 and 2002, a summary odds ratio of 1.4 (95% CI, 1.1,1.8) was estimated for the association between H. pylori infection and colorectal cancer risk. The graphical funnel plot appeared asymmetrical, but the formal statistical evaluations did not provide strong evidence of publication bias. The proportion of variation of study results because of heterogeneity was small (36.5%). Conclusions:, The results of our meta-analysis are consistent with a possible small increase in risk of colorectal cancer because of H. pylori infection. However, the possibility of some publication bias cannot be ruled out, although it could not be statistically confirmed. Larger, better designed and better controlled studies are needed to clarify the situation. [source] Cytokine gene polymorphisms in periodontal disease: a meta-analysis of 53 studies including 4178 cases and 4590 controlsJOURNAL OF CLINICAL PERIODONTOLOGY, Issue 9 2008Georgios K. Nikolopoulos Abstract Aim: We conducted a systematic review and a meta-analysis, in order to investigate the potential association of cytokine gene polymorphisms with either aggressive or chronic periodontal disease. Material and Methods: A comprehensive literature search was performed. We retrieved a total of 53 studies summarizing information about 4178 cases and 4590 controls. Six polymorphisms were included in our meta-analysis which are the following: IL-1A G[4845]T, IL-1A C[,889]T, IL-1B C[3953/4]T, IL-1B T[,511]C, IL-6 G[,174]C and TNFA G[,308]A. Random effect methods were used for the analysis. We calculated the specific odds ratios along with their 95% confidence intervals to compare the distribution of alleles and genotypes between cases and controls. Results and Conclusions: Using random effect methods we found statistically significant association of IL-1A C[,889]T and IL-1B C[3953/4]T polymorphisms with chronic periodontal disease without any evidence of publication bias or significant statistical heterogeneity. A weak positive association was also found concerning IL-1B T[,511]C and chronic periodontal disease. No association was found for all the cytokines examined as far as the aggressive form of the disease is concerned. Future studies may contribute to the investigation of the potential multigenetic predisposition of the disease and reinforce our findings. [source] A Meta-Analysis of the Effect of Common Currencies on International Trade,JOURNAL OF ECONOMIC SURVEYS, Issue 3 2005Andrew K. Rose Abstract., Thirty-four recent studies have investigated the effect of currency union on trade, resulting in 754 point estimates of this effect. This paper uses meta-analysis to combine, explain, and to summarize these disparate estimates of common currency trade effects. The hypothesis that there is no effect of currency union on trade is easily and robustly rejected at standard significance levels. Combining these estimates implies that a currency union increases bilateral trade by between 30 and 90%. Although there is evidence of publication selection, there is also evidence of a genuine positive trade effect beyond publication bias. [source] The effect of metformin on blood pressure, plasma cholesterol and triglycerides in type 2 diabetes mellitus: a systematic reviewJOURNAL OF INTERNAL MEDICINE, Issue 1 2004M. G. Wulffelé Abstract. Background., The UKPDS 34 showed that intensive treatment with metformin significantly reduces macrovascular end-points and mortality in individuals with newly diagnosed type 2 diabetes compared with intensive treatment with insulin or sulphonylurea derivatives, despite similar glycaemic control. How this should be explained is as yet unclear. We hypothesized that metformin may have a glucose-lowering independent effect on blood pressure and lipid profile. In order to test this hypothesis we systematically reviewed the literature and pooled the data obtained in a meta-analysis. Methods., Included were randomized-controlled trials in patients with type 2 diabetes mellitus and metformin treatment lasting at least 6 weeks. To identify all eligible trials we conducted electronic searches using the bibliographic databases Medline and Embase, contacted the manufacturer and checked obtained publications for cross-references. Results., Forty-one studies (3074 patients) provided data on blood pressure and/or lipid profile. When compared with control treatment, metformin associated effects on systolic and diastolic blood pressure and HDL cholesterol were small and statistically not significant [,1.09 mmHg 95% confidence interval (,3.01,0.82), P = 0.30; ,0.97 (,2.15,0.21) mmHg, P = 0.11 and +0.01 (,0.02,0.03) mmol L,1, P = 0.50, respectively]. Compared with control treatment, however, metformin decreased plasma triglycerides, total cholesterol and LDL cholesterol significantly [,0.13 (,0.21,,0.04) mmol L,1, P = 0.003; ,0.26 (,0.34,,0.18) mmol L,1, P < 0.0001 and ,0.22 (,0.31,,0.13) mmol L,1, P < 0.00001, respectively]. We found no indications for publication bias. Of note, glycaemic control as assessed by HbA1c was better with metformin than with control treatment [,0.74 (,0.84,,0.65) percentage point; P < 0.00001]. When studies were subdivided into tertiles according to increasing difference in glycaemic control between metformin and control treatment, it appeared that in case of near similar glycaemic control metformin had no effect versus control treatment on triglycerides, whereas still there was a significant effect on total and LDL cholesterol. Conclusions., This meta-analysis of randomized-controlled clinical trials suggests that metformin has no intrinsic effect on blood pressure, HDL cholesterol and triglycerides in patients with type 2 diabetes. This drug, however, independent of its effect on glycaemia, reduces total and LDL cholesterol significantly, but the reductions in these variables are relatively small. [source] A systematic review of controlled trials evaluating interventions in adult literacy and numeracyJOURNAL OF RESEARCH IN READING, Issue 2 2005Carole Torgerson This paper reports a systematic review of the quasi-experimental literature in the field of adult literacy and numeracy, published between 1980 and 2002. We included 27 controlled trials (CTs) that evaluated strategies and pedagogies designed to increase adult literacy and numeracy: 18 CTs with no effect sizes (incomplete data) and 9 CTs with full data. These nine trials are examined in detail for this paper. Of these nine trials, six evaluated interventions in literacy and three evaluated interventions in literacy and numeracy. Three of the nine trials showed a positive effect for the interventions, five trials showed no difference and one trial showed a positive effect for the control treatment. The quality of the trials was variable, but many of them had some methodological problems. There was no evidence of publication bias in the review. There have been few attempts to expose common adult literacy or numeracy programmes to rigorous evaluation and therefore in terms of policy and practice it is difficult to make any recommendations as to the type of adult education that should be supported. In contrast, however, the review does provide a strong steer for the direction to be taken by educational researchers: because of the present inadequate evidence base rigorously designed randomised controlled trials and quasi-experiments are required as a matter of urgency. [source] A systematic review and meta-analysis of randomised controlled trials evaluating interventions in adult literacy and numeracyJOURNAL OF RESEARCH IN READING, Issue 3 2003Carole J. Torgerson This paper reports a systematic review of the trial literature in the field of adult literacy and numeracy. The review was undertaken to investigate the effectiveness of teaching strategies and pedagogies designed to increase adult literacy and numeracy. The objectives were to search for and locate, synthesise and quality appraise all the randomised controlled trials aiming to evaluate interventions in adult literacy and/or numeracy, published between 1980 and 2002. Fifty-nine papers were included in the descriptive map. Twelve papers were included that contained nine randomised controlled trials. All of the trials included in the review were of high quality in the sense that they had adopted an appropriate study design for assessing effectiveness. However, within that study design many of the studies had methodological problems, for example: small sample size and lack of justification of sample size calculation; unclear method of random allocation; high attrition rate and lack of ,intention to teach' analysis. There was evidence of publication bias. Pooling three studies that compared teaching against no teaching showed a strong, positive and statistically significant effect on outcome. Two other studies examined the use of computer-assisted instruction (CAI) on literacy among imprisoned adults. Pooling these two studies showed a modest but not statistically significant benefit. There is a dearth of rigorous RCTs in the field of adult literacy and numeracy. The evidence is suggestive of a benefit of adult literacy and numeracy interventions; however, because of the heterogeneity of studies, the precise role of any intervention is uncertain and this finding may be undermined by the presence of substantial publication bias. We recommend that a series of large, well-designed and well-conducted randomised trials should be undertaken in the field of adult literacy and numeracy. [source] The Efficacy of Acamprosate in the Maintenance of Abstinence in Alcohol-Dependent Individuals: Results of a Meta-AnalysisALCOHOLISM, Issue 1 2004Karl Mann Abstract: Background: A number of clinical trials have been undertaken to determine the efficacy of acamprosate in the maintenance of abstinence in alcohol-dependent individuals. However, the reported differences in patient populations, treatment duration, and study endpoints make comparisons difficult. An assessment of the efficacy of treatment with acamprosate was, therefore, undertaken using meta-analytical techniques. Methods: All randomized, placebo-controlled trials (RCTs) that fulfilled predetermined criteria were identified using (1) a language unrestricted search of 10 electronic databases; (2) a manual search of relevant journals, symposia, and conference proceedings; (3) cross-referencing of all identified publications; (4) personal communications with investigators; and (5) scrutiny of Merck-Santé's internal reports of all European trials. Study quality was assessed, independently, by three blinded workers. Key outcome data were identified; some outcome variables were recalculated to ensure consistency across trials. The primary outcome measure was continuous abstinence at 6 months; abstinence rates were determined by estimating Relative Benefit (RB). Results: A total of 19 published 1 unpublished RCTs were identified that fulfilled the selection criteria; 3 were excluded because the documentation available was insufficient to allow adequate assessment. The remaining 17 studies, which included 4087 individuals, 53% of whom received active drug, were of good quality and were otherwise reasonably comparable. There was no evidence of publication bias. Continuous abstinence rates at 6 months were significantly higher in the acamprosate-treated patients (acamprosate, 36.1%; placebo, 23.4%; RB, 1.47; [95% confidence intervals (CI): 1.29,1.69]; p < 0.001). This effect was observed independently of the method used for assigning missing data. The effect sizes in abstinent rates at 3, 6, and 12 months were 1.33, 1.50, and 1.95, respectively. At 12 months, the overall pooled difference in success rates between acamprosate and placebo was 13.3% (95% CI, 7.8,18.7%; number needed to treat, 7.5). Acamprosate also had a modest but significant beneficial effect on retention (6.01%; [95% CI, 2.90,8.82]; p= 0.0106). Conclusion:: Acamprosate has a significant beneficial effect in enhancing abstinence in recently detoxified, alcohol-dependent individuals. [source] Association between the PD1.3A/G polymorphism of the PDCD1 gene and systemic lupus erythematosus in European populations: a meta-analysisJOURNAL OF THE EUROPEAN ACADEMY OF DERMATOLOGY & VENEREOLOGY, Issue 4 2009J-L Liu Abstract Background, Linkage studies suggest a locus, SLEB2, involved in susceptibility to systemic lupus erythematosus (SLE) and programmed cell death 1 (PDCD1) gene locates in this region. The association of PDCD1 polymorphism (PD1.3A/G) with SLE has been widely investigated, but there are no unambiguous conclusions. Objective, To assess the combined evidence for the association between PD1.3A/G polymorphism and SLE and to summarize the effect size of the polymorphism associated with susceptibility to SLE. Methods, We surveyed studies on the PD1.3A/G polymorphism and SLE using comprehensive PubMed search up to May 2008. The pooled odds ratio (OR) was calculated using a fixed- or a random-effects model. Heterogeneity was identified by sensitivity analysis and publication bias was examined by funnel plot and Egger's test. We also computed the power for a given number of samples. Results, A total of 20 datasets from eight studies that met our inclusion criteria were included. The studies comprised of a total of 2909 cases and 3995 controls. Stratified meta-analysis demonstrated a significant association between PD1.3A and SLE among non-Spanish European descents [OR, 1.290; 95% confidence interval (95% CI), 1.098,1.516; z = 3.10, P = 0.002], while PD1.3G is the risk allele in Spanish populations (OR = 1.414, 95% CI = 1.075,1.862; z = 2.48, P = 0.013). Both results have sufficient power to support these findings. No publication bias presented in the studies analysed. Conclusions, This meta-analysis demonstrates a significant association between PD1.3A and SLE among non-Spanish European descents, while a negative association was observed in Spanish population. Conflicts of interest None declared [source] Recurrence of autoimmune liver disease after liver transplantation: A systematic reviewLIVER TRANSPLANTATION, Issue 12 2006Manjushree Gautam Recurrence of autoimmune liver disease in allografts has long been a topic of debate. We conducted a systematic review of the literature to examine the reported incidence of recurrence after liver transplantation of primary biliary cirrhosis (PBC), primary sclerosing cholangitis (PSC), and autoimmune hepatitis (AIH). The MEDLINE, EMBASE, and Cochrane electronic databases were used to identify articles. The inclusion criteria used were articles on patients with at least 90 days of posttransplantation follow-up, histologic criteria for diagnosis of PBC and AIH recurrence, radiologic or histologic criteria or both for diagnosis of PSC recurrence, and exclusion of other causes of liver disease causing similar histologic findings. Incidence in individual studies was combined to calculate the overall recurrence. Risk factors were analyzed whenever crude data were available. Funnel plots were used to assess publication bias. Out of 90 articles identified, 43 met criteria for systematic review (PBC, 16; PSC, 14; AIH, 13). The calculated weighted recurrence rate was 18% for PBC, 11% for PSC, and 22% for AIH. No difference was found in PBC and AIH recurrence by type of primary immunosuppression. There were not enough data to assess this issue in PSC studies. There was evidence of publication bias among PSC and AIH studies but not among PBC studies. In conclusion, recurrence of autoimmune liver disease after liver transplantation appears to be a real concern. As these patients are followed long-term, recurrence of disease may become the primary cause of morbidity. Liver Transpl 12:1813-1824, 2006. © 2006 AASLD. [source] How international is Medical Education?MEDICAL EDUCATION, Issue 1 2004L J Brice Aims To consider Medical Education's claim to international status in terms of the extent of international authorship within published articles, the degree to which authors draw on the international literature to support their work, and its self-citation rates and publication decisions. Method We examined 6 journals' citation rates for the period 1997,2001 to see if there was evidence of national publication bias; we calculated their self-citation rates to see if this had any influence on impact factor, and we examined Medical Education's management files for trends which might indicate publication bias due to country of origin of authors. Results All 6 journals exhibited a bias in favour of citing journals from their own countries. The US journals were more likely to cite journals from their own country. Medical Education was most likely to cite journals from non-UK countries. Self-citation rates did not appear to affect impact factors. The ratio of UK to non-UK papers published in Medical Education has not changed significantly over the period studied although non-UK submissions increased sharply in 2002 and the number of North American submissions has doubled since 1998. Conclusion Medical Education is justified in calling itself an international journal to the extent that the majority of papers it publishes are from countries other than the UK, and it is more likely than other journals in the field to publish papers which cite work in journals published outside the UK. Nevertheless, there is some evidence of publication bias in the journal and more work is needed to discover why this is the case. Various strategies to address the issue of national bias in Medical Education are discussed. [source] Paramedical treatment in primary dystonia: A systematic review,MOVEMENT DISORDERS, Issue 15 2009Cathérine C.S. Delnooz MD Abstract Dystonia is a disabling movement disorder with a significant impact on quality of life. The current therapeutic armamentarium includes various drugs, botulinum toxin injections, and occasionally (neuro)surgery. In addition, many patients are referred for paramedical (including allied health care) interventions. An enormous variation in the paramedical treatment is provided, largely because evidence-based, accepted treatment regimes are not available. We have conducted a systematic review of studies that explored the effect of various paramedical interventions in primary dystonia. Only studies that have used clinical outcome measures were included. There were no class A1 or A2 studies and therefore, level 1 or 2 practice recommendations for a specific intervention could not be deducted. Many papers were case reports, mostly with a very limited number of patients and a clear publication bias for beneficial effects of a particular paramedical intervention. Some potentially interesting interventions come from class B studies, which include physical therapy in addition to botulinum toxin injections (BoNT-A) in cervical dystonia; sensorimotor training and transcutaneous electrical nerve stimulation (TENS) in writer's cramp; and speech therapy added to BoNT-A injections in laryngeal dystonia. Good quality clinical studies are therefore warranted, which should have the aim to be generally applicable. A design in which the paramedical intervention is added to a current gold standard, for example, BoNT-A injections in cervical dystonia, is recommended. © 2009 Movement Disorder Society [source] | |||||||||||||||||||||||||||||||