Approaches to heterogeneity in meta-analysis

Golgi protein 73 versus alpha-fetoprotein as a biomarker for hepatocellular carcinoma: a diagnostic meta-analysis

Backgrounds

There have been conflicting reports about serum golgi protein 73 (GP73) as one of the most promising serum markers for the diagnosis of hepatocellular carcinoma (HCC). This study was to make a systematic review about the diagnostic accuracy of serum GP73 versus alpha-fetoprotein (AFP) for HCC.

Methods

After a systematic review of related studies, sensitivity, specificity and other measures about the accuracy of serum GP73 and AFP in the diagnosis of HCC were pooled using random-effects models. Summary receiver operating characteristic curve analysis was used to summarize the overall test performance.

Results

Eight studies were included in our meta-analysis. The summary estimates for serum GP73 and AFP in diagnosing HCC in the studies included were as follows: sensitivity, 76% (95% confidence interval (CI) 51-91%) vs. 70% (47-86%); specificity, 86% (95%CI 65-95%) vs. 89% (69-96%); diagnostic odds ratio (DOR), 18.59 (95%CI 5.33-64.91) vs. 18.00(9.41-34.46); and area under sROC, 0.88 (95%CI 0.77-0.99) vs. 0.86 (95%CI 0.84-0.87).

Conclusions

The current evidence indicates that serum GP73 has a comparable accuracy to AFP for the diagnosis of HCC, while the value of serum GP73 in combination with AFP for HCC detection deserves further investigation.

Evaluation of PCR on bronchoalveolar lavage fluid for diagnosis of invasive aspergillosis: a bivariate metaanalysis and systematic review

Background

Nucleic acid detection by polymerase chain reaction (PCR) is emerging as a sensitive and rapid diagnostic tool. PCR assays on serum have the potential to be a practical diagnostic tool. However, PCR on bronchoalveolar lavage fluid (BALF) has not been well established. We performed a systematic review of published studies to evaluate the diagnostic accuracy of PCR assays on BALF for invasive aspergillosis (IA).

Methods

Relevant published studies were shortlisted to evaluate the quality of their methodologies. A bivariate regression approach was used to calculate pooled values of the method sensitivity, specificity, and positive and negative likelihood ratios. Hierarchical summary receiver operating characteristic curves were used to summarize overall performance. We calculated the post-test probability to evaluate clinical usefulness. Potential heterogeneity among studies was explored by subgroup analyses.

Results

Seventeen studies comprising 1191 at-risk patients were selected. The summary estimates of the BALF-PCR assay for proven and probable IA were as follows: sensitivity, 0.91 (95% confidence interval (CI), 0.79–0.96); specificity, 0.92 (95% CI, 0.87–0.96); positive likelihood ratio, 11.90 (95% CI, 6.80–20.80); and negative likelihood ratio, 0.10 (95% CI, 0.04–0.24). Subgroup analyses showed that the performance of the PCR assay was influenced by PCR assay methodology, primer design and the methods of cell wall disruption and DNA extraction.

Conclusions

PCR assay on BALF is highly accurate for diagnosing IA in immunocompromised patients and is likely to be a useful diagnostic tool. However, further efforts towards devising a standard protocol are needed to enable formal validation of BALF-PCR.

Hepatitis C virus and the immunological response to hepatitis B virus vaccine in dialysis patients: meta-analysis of clinical studies

It is well known that the seroconversion rate of patients following hepatitis B virus (HBV) vaccination is lower in uraemic than healthy subjects. A variety of inherited or acquired factors have been implicated in this diminished response, and the high prevalence of hepatitis C virus (HCV) infection among patients on maintenance dialysis has been suggested to play a role. However, the impact of HCV on the immune response to HB vaccine in patients receiving long-term dialysis is not entirely understood. Here, we evaluate the influence of HCV infection on the immunological response to HBV vaccine in dialysis population by performing a systematic review of the literature with a meta-analysis of clinical studies.We used the random-effects model of DerSimonian and Laird with heterogeneity and sensitivity analyses. The end-point of interest was the rate of patients showing seroprotective anti-hepatitis B titres at completion of HBV vaccine schedule among HCV-positive versus HCV-negative patients on chronic dialysis. We identified eight studies involving 520 unique patients on long-term dialysis. Aggregation of study results did not show a significant decrease in response rates among HCV-infected versus noninfected patients [pooled odds ratio = 0.621 (95% CI, 0.285; 1.353)]. The P-value was 0.007 for our test of study heterogeneity. Stratified analysis in various subgroups of interest did not meaningfully change our results. Our meta-analysis showed no association between immunological response to hepatitis B vaccine and HCV infection in individuals on long-term dialysis. These results support the use of recombinant vaccine against hepatitis B in patients on regular dialysis with HCV infection.

Pleural fluid soluble triggering receptor expressed on myeloid cells-1 as a marker of bacterial infection: a meta-analysis

Background

Pleural infection is a common clinical problem. Its successful treatment depends on rapid diagnosis and early initiation of antibiotics. The measurement of soluble triggering receptor expressed in myeloid cells-1 (sTREM-1) level in pleural effusions has proven to be a valuable diagnostic tool for differentiating bacterial effusions from effusions of other etiologies. Herein, we performed a meta-analysis to assess the accuracy of pleural fluid sTREM-1 in the diagnosis of bacterial infection.

Methods

We searched Web of Knowledge and Medline from 1990 through March 2011 for studies reporting diagnostic accuracy data regarding the use of sTREM-1 in the diagnosis of bacterial pleural effusions. Pooled sensitivity and specificity and summary measures of accuracy and Q* were calculated.

Results

Overall, the sensitivity of sTREM-1was 78% (95% CI: 72%-83%); the specificity was 84% (95% CI: 80%-87%); the positive likelihood ratio was 6.0 (95% CI: 3.3-10.7); and the negative likelihood ratio was 0.22 (95% CI: 0.12-0.40). The area under the SROC curve for sTREM-1 was 0.92. Statistical heterogeneity and inconsistency were found for sensitivity (p = 0.015, χ² = 15.73, I² = 61.9%), specificity (p = 0.000, χ² = 29.90, I² = 79.9%), positive likelihood ratio (p = 0.000, χ² = 33.09, I² = 81.9%), negative likelihood ratio (p = 0.008, χ² = 17.25, I² = 65.2%), and diagnostic odds ratio (p = 0.000, χ² = 28.49, I² = 78.9%). A meta-regression analysis performed showed that the Quality Assessment of Diagnostic Accuracy Studies score (p = 0.3245; RDOR, 4.34; 95% CI, 0.11 to 164.01), the Standards for Reporting of Diagnostic Accuracy score (p = 0.3331; RDOR, 1.70; 95% CI, 0.44 to 6.52), lack of blinding (p = 0.7439; RDOR, 0.60; 95% CI, 0.01 to 33.80), and whether the studies were prospective or retrospective studies (p = 0.2068; RDOR, 7.44; 95% CI, 0.18 to 301.17) did not affect the test accuracy. A funnel plot for publication bias suggested a remarkable trend of publication bias.

Conclusions

Our findings suggest that sTREM-1 has a good diagnostic accuracy and may provide a useful adjunctive tool for the diagnosis of bacterial pleural effusions. However, further studies are needed in order to identify any differences in the diagnostic performance of sTREM-1 of parapneumonic effusions and empyemas.

Intradermal vs intramuscular vaccine against hepatitis B infection in dialysis patients: a meta-analysis of randomized trials

Chronic dialysis patients are at risk of contracting hepatitis B virus infection and have a diminished immune response to hepatitis B virus vaccine. Recent reports support intradermal administration of hepatitis B virus vaccine in patients on regular dialysis but the efficacy and safety of this approach remain unclear. We conducted a meta-analysis of randomized, controlled clinical trials to compare seroprotection achieved by intradermal vs intramuscular hepatitis B vaccine, in patients on maintenance dialysis. Meta-analysis of data from 718 adults (14 trials) on long-term dialysis demonstrated that intramuscular hepatitis B vaccination was less likely to achieve seroprotection than intradermal vaccination, the pooled odds ratio was 0.454 (95% CI, 0.3; 0.67), P = 0.001. The test of study heterogeneity was not significant. This difference did not persist during follow-up (6-60 months after completing vaccine schedule), the pooled odds ratio being 0.718 (95% CI, 0.36; 1.47), NS. Some evidence of significant heterogeneity including publication bias was present but stratified analysis in various subgroups showed that this issue did not meaningfully change our results. Intradermal hepatitis B vaccine was safe and well tolerated. We conclude that intradermal hepatitis B vaccine induces a superior response rate compared to intramuscular route at completion of vaccine cycle, despite a lower vaccine dose. No significant advantage was found over longer follow-up. It remains unclear whether the higher seroprotection rate achieved with intradermal route translates into a lower frequency of de novo hepatitis B among patients on maintenance dialysis.

Diagnostic value of anti-cyclic citrullinated peptide antibody for rheumatoid arthritis in a Chinese population: a meta-analysis

To use meta-analysis to determine the accuracy of anti-cyclic citrullinated peptide (CCP) antibody in diagnosis of patients with rheumatoid arthritis (RA) in a Chinese population, we searched MEDLINE and CNKI databases for studies published in English or Chinese between January 2000 and June 2010. Two investigators independently evaluated studies for inclusion, data extraction, and quality assessment. We used a random-effects model to combine estimates of sensitivity, specificity, positive likelihood ratio (LR+), negative likelihood ratio (LR-), and diagnostic odds ratio (DOR). One hundred and eighteen studies met our inclusion criteria. All studies were of high quality. The summary estimates for anti-CCP antibody in the diagnosis of RA in a Chinese population were as follows: sensitivity 0.65 (95% confidence interval (CI) 0.65-0.66), specificity 0.95 (95% CI 0.95-0.96), positive likelihood ratio (LR+) 15.84 (95% CI 13.55-18.54), negative likelihood ratio (LR-) 0.33 (95% CI 0.31-0.35), and diagnostic odds ratio (DOR) 51.60 (95% CI 43.64-61.01). With high specificity and moderate sensitivity, anti-CCP antibody tests play an important role in conforming the diagnosis of RA in a Chinese population.

Diagnostic accuracy of T-cell interferon-γ release assays in tuberculous pleurisy: a meta-analysis

BACKGROUND AND OBJECTIVE

The diagnosis of tuberculous pleurisy by analysis of pleural fluid using standard diagnostic tools is difficult. Recently, T-cell interferon-γ release assays (IGRA) have been introduced for the diagnosis of tuberculous pleurisy. The aim of the present meta-analysis was to establish the overall diagnostic accuracy of IGRA on both pleural fluid and peripheral blood, for diagnosing tuberculous pleurisy.

METHODS

A systematic review was performed of English language publications. Sensitivity, specificity and other measures of the accuracy of IGRA for the diagnosis tuberculous pleurisy using both pleural fluid and blood were pooled using a random-effects model or a fixed-effects model. Receiver operating characteristic curves were used to summarize overall test performance.

RESULTS

Seven out of eight studies met the inclusion criteria. The summary estimates of sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, positive predictive value, negative predictive value and diagnostic odds ratio were, for pleural fluid: 0.75, 0.82, 3.49, 0.24, 0.85, 0.70 and 19.04, respectively; and for blood: 0.80, 0.72, 2.86, 0.28, 0.78, 0.74 and 11.06, respectively.

CONCLUSIONS

As almost 20% of non-tuberculosis patients would be erroneously treated for tuberculosis and 25% of patients with tuberculous pleurisy would be missed, pleural fluid IGRA are not useful for the clinical diagnosis of tuberculous pleurisy.

Strong association of 677 C>T substitution in the MTHFR gene with male infertility--a study on an indian population and a meta-analysis

Background

Methylenetetrahydrofolate reductase (MTHFR) is an important enzyme of folate and methionine metabolism, making it crucial for DNA synthesis and methylation. The objective of this study was to analyze MTHFR gene 677C>T polymorphism in infertile male individuals from North India, followed by a meta-analysis on our data and published studies.

Methodology/Principal Findings

We undertook genotyping on a total of 837 individuals including well characterized infertile (N = 522) and confirmed fertile (N = 315) individuals. The SNP was typed by direct DNA sequencing. Chi square test was done for statistical analysis. Published studies were searched using appropriate keywords. Source of data collection for meta-analysis included ‘Pubmed’, ‘Ovid’ and ‘Google Scholar’. Those studies analyzing 677C>T polymorphism in male infertility and presenting all relevant data were included in meta-analysis. The genotype data for infertile subjects and fertile controls was extracted from each study. Chi square test was done to obtain odds ratio (OR) and p-value. Meta-analysis was performed using Comprehensive Meta-analysis software (Version 2). The frequency of mutant (T) allele (p = 0.0025) and genotypes (CT+TT) (p = 0.0187) was significantly higher in infertile individuals in comparison to fertile controls in our case-control study. The overall summary estimate (OR) for allele and genotype meta-analysis were 1.304 (p = 0.000), 1.310 (p = 0.000), respectively, establishing significant association of 677C>T polymorphism with male infertility.

Conclusions/Significance

677C>T substitution associated strongly with male infertility in Indian population. Allele and genotype meta-analysis also supported its strong correlation with male infertility, thus establishing it as a risk factor.

Testing for homogeneity in meta-analysis I. The one-parameter case: standardized mean difference

Meta-analysis seeks to combine the results of several experiments in order to improve the accuracy of decisions. It is common to use a test for homogeneity to determine if the results of the several experiments are sufficiently similar to warrant their combination into an overall result. Cochran's Q statistic is frequently used for this homogeneity test. It is often assumed that Q follows a chi-square distribution under the null hypothesis of homogeneity, but it has long been known that this asymptotic distribution for Q is not accurate for moderate sample sizes. Here, we present an expansion for the mean of Q under the null hypothesis that is valid when the effect and the weight for each study depend on a single parameter, but for which neither normality nor independence of the effect and weight estimators is needed. This expansion represents an order O(1/n) correction to the usual chi-square moment in the one-parameter case. We apply the result to the homogeneity test for meta-analyses in which the effects are measured by the standardized mean difference (Cohen's d-statistic). In this situation, we recommend approximating the null distribution of Q by a chi-square distribution with fractional degrees of freedom that are estimated from the data using our expansion for the mean of Q. The resulting homogeneity test is substantially more accurate than the currently used test. We provide a program available at the Paper Information link at the Biometrics website http://www.biometrics.tibs.org for making the necessary calculations.

Combined antiviral therapy of hepatitis C virus in dialysis patients: meta-analysis of clinical trials

The efficacy and safety of combined interferon (IFN) plus ribavirin in patients on long-term dialysis and chronic hepatitis C remains unclear, although a number of small clinical trials have addressed this issue. We evaluated the efficacy and safety of combination antiviral therapy (conventional or pegylated interferon plus ribavirin) in dialysis patients with chronic hepatitis C by performing a systematic review of the literature with a meta-analysis of clinical trials. The primary outcome was sustained virological response (SVR) (as a measure of efficacy); the secondary outcome was drop-out rate (as a measure of tolerability). We used the random effects model of Der Simonian and Laird, with heterogeneity and sensitivity analyses. We identified 10 clinical studies (151 unique patients), one (10%) of which was a controlled clinical trial. Most (97.4%) patients were on long-term haemodialysis. The summary estimate for SVR and drop-out rate was 56% [95% Confidence Intervals (95% CI) 28-84] and 25% (95% CI, 10-40), respectively. The most frequent side effects requiring interruption of treatment were anaemia (26%) and heart failure (9%). These results occurred irrespective of type of interferon (conventional or peg-IFN, peg-IFNalfa-2a or alfa-2b), trial design (controlled or cohort study), or clinical characteristics of patients (naïve, nonresponders or relapsers). The studies were heterogeneous with regard to SVR and drop-out rate. Combination antiviral therapy (interferon plus ribavirin) gives encouraging results in terms of efficacy and safety among dialysis patients even if the limited number of patients enrolled in our meta-analysis hampers definitive conclusions.

A meta-analysis of the efficacy of nonphysician brief interventions for unhealthy alcohol use: implications for the patient-centered medical home

Brief physician interventions can reduce alcohol consumption. Physicians may not have the time to provide brief interventions, and it is unclear whether nonphysicians can do so effectively. We conducted a systematic review and meta-analysis to examine the efficacy of brief interventions by nonphysician clinicians for unhealthy alcohol use. We searched the English-language literature in MEDLINE and other databases covering the domains of alcohol problems, primary care, nonphysician, and brief interventions. Studies of brief interventions delivered at least in part by nonphysicians in primary care and examining drinking outcomes were included. Sensitivity analyses examined the effect of excluding studies that contributed disproportionately to the heterogeneity of results. Thirteen studies, conducted 1996-2008, met our criteria. Seven studies with a total of 2,633 patients were included in the meta-analysis. Nonphysician interventions were associated with 1.7 (95% confidence interval [CI]=-.03 to -3.5) fewer standard drinks per week than control conditions (p = .054). Excluding the one study that increased heterogeneity, the effect was smaller but reached statistical significance; nonphysician counseling was associated with 1.4 (95% CI = .3- 2.4) fewer standard drinks per week compared to control (p = .012). Nonphysician brief interventions are modestly effective at reducing drinking in primary care patients with unhealthy alcohol use.

Glucagon-like peptide-1 receptor agonists and cardiovascular events: a meta-analysis of randomized clinical trials

Objective. Data from randomized clinical trials with metabolic outcomes can be used to address concerns about potential issues of cardiovascular safety for newer drugs for type 2 diabetes. This meta-analysis was designed to assess cardiovascular safety of GLP-1 receptor agonists. Design and Methods. MEDLINE, Embase, and Cochrane databases were searched for randomized trials of GLP-1 receptor agonists (versus placebo or other comparators) with a duration ≥12 weeks, performed in type 2 diabetic patients. Mantel-Haenszel odds ratio with 95% confidence interval (MH-OR) was calculated for major cardiovascular events (MACE), on an intention-to-treat basis, excluding trials with zero events. Results. Out of 36 trials, 20 reported at least one MACE. The MH-OR for all GLP-1 receptor agonists was 0.74 (0.50–1.08), P = .12 (0.85 (0.50–1.45), P = .55, and 0.69 (0.40–1.22), P = .20, for exenatide and liraglutide, resp.). Corresponding figures for placebo-controlled and active comparator studies were 0.46 (0.25–0.83), P = .009, and 1.05 (0.63–1.76), P = .84, respectively. Conclusions. To date, results of randomized trials do not suggest any detrimental effect of GLP-1 receptor agonists on cardiovascular events. Specifically designed longer-term trials are needed to verify the possibility of a beneficial effect.

Long-term prevention of mortality in morbid obesity through bariatric surgery. a systematic review and meta-analysis of trials performed with gastric banding and gastric bypass

BACKGROUND

Bariatric surgery has been reported to reduce long-term mortality in operated participants in comparison with nonoperated participants.

METHODS

We performed a systematic review and meta-analysis of clinical trials published as full articles dealing with cardiovascular (CV) mortality, all-cause mortality (noncardiovascular), and global mortality (sum of CV and all-cause mortality). Pooled-fixed effects of estimates of the risk of mortality in participants undergoing surgery were calculated compared with controls.

RESULTS

Of 44,022 participants from 8 trials (14,052 undergoing surgery and 29,970 controls), death occurred in 3317 participants (400 in surgery, 2917 in controls); when the kind of death was specified, 321 CV deaths (118 in surgery, 203 in controls), and 523 all-cause deaths (218 in surgery, 305 in controls) occurred. Compared with controls, surgery was associated with a reduced risk of global mortality (OR = 0.55, CI, 0.49-0.63), of CV mortality (OR = 0.58, CI, 0.46-0.73), and of all-cause mortality (OR = 0.70, CI, 0.59-0.84).Data of all-cause mortality were not heterogeneous; heterogeneity of data of CV mortality decreased when studies were grouped according to size (large vs small studies). The reduction of risk was smaller in large than in small studies (OR = 0.61 vs 0.21, 0.63 vs 0.16, 0.74 vs 0.35 for global, CV, and all-cause mortality, respectively). The effect of gastric banding and gastric by-pass (3797 vs 10,255 interventions) was similar for global and all-cause mortality (OR = 0.57 vs 0.55, and 0.66 vs 0.70, respectively), different for CV mortality (OR = 0.71 vs 0.48). At meta-regression analysis, a trend for a decrease of global mortality (Log OR) linked to increasing BMI appeared.

CONCLUSION

This meta-analysis indicates that (1) bariatric surgery reduces long-term mortality; (2) risk reduction is smaller in large than in small studies; and (3) both gastric banding and gastric by-pass reduce mortality with a greater effect of the latter on CV mortality.

Meta-analysis: the impact of diabetes mellitus on the immunological response to hepatitis B virus vaccine in dialysis patients

BACKGROUND

Patients on maintenance dialysis typically show a suboptimal immune response to hepatitis B virus vaccine compared with the non-uraemic population. A variety of inherited or acquired factors have been implicated in this diminished response. It is well known that patients with diabetes mellitus have a compromised immune system, and diabetic nephropathy is an important cause of chronic kidney disease. However, the impact of diabetes mellitus on the immune response to HBV vaccine in patients receiving long-term dialysis remains unclear.

AIM

To evaluate the influence of diabetes mellitus on the immune response to HBV vaccine in dialysis population by performing a systematic review of the literature with a meta-analysis of clinical studies.

METHODS

We used the random effects model of DerSimonian and Laird with heterogeneity and sensitivity analyses. The end-point of interest was the rate of patients showing seroprotective antibody against hepatitis B surface antigen at completion of vaccine schedule in the diabetic vs. the nondiabetic dialysis individuals.

RESULTS

We identified 12 studies involving 1002 unique patients on long-term dialysis. Aggregation of study results showed a significant decrease in response rates among the diabetic vs. the nondiabetic patients [pooled odds ratio=0.52 (95% CI 0.38-0.71)]. The P-value was 0.29 for our test of study heterogeneity. Stratified analysis in various subgroups of interest did not meaningfully change our results.

CONCLUSIONS

Our meta-analysis showed a clear association between diabetes mellitus and impaired response to hepatitis B virus vaccine in individuals on long-term dialysis. Such a relationship is biologically plausible. Vaccination schedules with adapted vaccine doses and frequent serum testing for loss of immunity against hepatitis B virus should be considered in patients on maintenance dialysis with diabetes mellitus.

Physical activity before and during pregnancy and risk of gestational diabetes mellitus: a meta-analysis

OBJECTIVE

Gestational diabetes mellitus (GDM) is one of the most common complications of pregnancy and is associated with a substantially elevated risk of adverse health outcomes for both mothers and offspring. Physical activity may contribute to the prevention of GDM and thus is crucial for dissecting the vicious circle involving GDM, childhood obesity, and adulthood obesity, and diabetes. Therefore, we aimed to systematically review and synthesize the current evidence on the relation between physical activity and the development of GDM.

RESEARCH DESIGN AND METHODS

Medline, EMBASE, and Cochrane Reviews were searched from inception to 31 March 2010. Studies assessing the relationship between physical activity and subsequent development of GDM were included. Characteristics including study design, country, GDM diagnostic criteria, ascertainment of physical activity, timing of exposure (prepregnancy or early pregnancy), adjusted relative risks, CIs, and statistical methods were extracted independently by two reviewers.

RESULTS

Our search identified seven prepregnancy and five early pregnancy studies, including five prospective cohorts, two retrospective case-control studies, and two cross-sectional study designs. Prepregnancy physical activity was assessed in 34,929 total participants, which included 2,813 cases of GDM, giving a pooled odds ratio (OR) of 0.45 (95% CI 0.28-0.75) when the highest versus lowest categories were compared. Exercise in early pregnancy was assessed in 4,401 total participants, which included 361 cases of GDM, and was also significantly protective (0.76 [95% CI 0.70-0.83]).

CONCLUSIONS

Higher levels of physical activity before pregnancy or in early pregnancy are associated with a significantly lower risk of developing GDM.

Performance of statistical methods for meta-analysis when true study effects are non-normally distributed: A simulation study

Meta-analysis (MA) is a statistical methodology that combines the results of several independent studies considered by the analyst to be 'combinable'. The simplest approach, the fixed-effects (FE) model, assumes the true effect to be the same in all studies, while the random-effects (RE) family of models allows the true effect to vary across studies. However, all methods are only correct asymptotically, while some RE models assume that the true effects are normally distributed. In practice, MA methods are frequently applied when study numbers are small and the normality of the effect distribution unknown or unlikely. In this article, we discuss the performance of the FE approach and seven frequentist RE MA methods: DerSimonian-Laird, Q-based, maximum likelihood, profile likelihood, Biggerstaff-Tweedie, Sidik-Jonkman and Follmann-Proschan. We covered numerous scenarios by varying the MA sizes (small to moderate), the degree of heterogeneity (zero to very large) and the distribution of the effect sizes (normal, skew-normal and 'extremely' non-normal). Performance was evaluated in terms of coverage (Type I error), power (Type II error) and overall effect estimation (accuracy of point estimates and error intervals).

Diagnostic value of transthoracic Doppler echocardiography in pulmonary hypertension: a meta-analysis

BACKGROUND

A commonly used noninvasive method, transthoracic Doppler echocardiography (TDE) has been widely recommended for the diagnosis of pulmonary hypertension (PH). We aimed to review comprehensively the evidence for the use of TDE to diagnose PH.

METHODS

After a systematic review of English-language studies, we used random-effects models to pool sensitivity, specificity, and other measures of accuracy of TDE for the diagnosis of PH. Summary receiver operating characteristic (SROC) curves were used to summarize overall test performance.

RESULTS

Six studies met our inclusion criteria. The summary estimates for TDE in the diagnosis of PH in the included studies were as follows: sensitivity, 0.82 (95% confidence interval (CI), 0.76-0.88); specificity, 0.68 (95% CI, 0.64-0.72); positive likelihood ratio (PLR), 2.88 (95% CI, 1.77-4.70); negative likelihood ratio (NLR), 0.31 (95% CI, 0.18-0.53); and diagnostic odds ratio (DOR), 11.36 (95% CI, 4.62-27.94).

CONCLUSIONS

Current evidence suggests that TDE is a test with acceptable mixed sensitivity, but in isolation, it has insufficient specificity for detecting PH. It may be useful as a first-line surveillance modality in patients in whom PH is suspected. The value of the combination of TDE with other noninvasive methods for PH detection warrants further investigation.

Value of diffusion-weighted magnetic resonance images for discrimination of focal benign and malignant hepatic lesions: a meta-analysis

PURPOSE

To evaluate the ability of DW-MRI in differentiating malignant hepatic tumors from benign lesions.

MATERIALS AND METHODS

Meta-analysis of 14 diagnostic studies was used. A systematic search in Medline, Embase, Web of Science (from January, 1966, to October, 2009), and Cochrane Controlled Clinical Trials Register Database (through third Quarter 2009) was used with screening of the literature.

RESULTS

A meta-analysis of all 95 published studies was performed. Fourteen studies fulfilled the inclusion criteria (804 patients with 1665 hepatic lesions). The global sensitivity was 0.91 (95% confidence interval [CI], 0.86-0.94), the specificity was 0.93 (95% CI, 0.86-0.97), the positive likelihood ratio (PLR) was 13.10 (95% CI, 6.30-27.26), the negative likelihood ratio (NLR) was 0.10 (95% CI, 0.06-0.15), and the diagnostic odds ratio (DOR) was 133.76 (95% CI, 49.77-359.45). The area under the curve of the summary receiver operator characteristic (SROC) was 0.96 (95% CI 0.94-0.98).

CONCLUSION

Diffusion-weighted magnetic resonance imaging is potential technically feasible to differentiate malignant from benign focal liver lesions. Apparent diffusion coefficient measurements can be useful in providing rapid quantifiable information.

Infections in patients with cirrhosis increase mortality four-fold and should be used in determining prognosis

BACKGROUND & AIMS

A staged prognostic model of cirrhosis based on varices, ascites, and bleeding has been proposed. We analyzed data on infections in patients with cirrhosis to determine whether it is also a prognostic factor.

METHODS

Studies were identified by MEDLINE, EMBASE, COCHRANE, and ISI Web of Science searches (1978-2009); search terms included sepsis, infection, mortality, and cirrhosis. Studies (n = 178) reporting more than 10 patients and mortality data were evaluated (225 cohorts, 11,987 patients). Mortality after 1, 3, and 12 months was compared with severity, site, microbial cause of infection, etiology of cirrhosis, and publication year. Pooled odds ratio of death was compared for infected versus noninfected groups (18 cohorts, 2317 patients).

RESULTS

Overall median mortality of infected patients was 38%: 30.3% at 1 month and 63% at 12 months. Pooled odds ratio for death of infected versus noninfected patients was 3.75 (95% confidence interval, 2.12-4.23). In 101 studies that reported spontaneous bacterial peritonitis (7062 patients), the median mortality was 43.7%: 31.5% at 1 month and 66.2% at 12 months. In 30 studies that reported bacteremia (1437 patients), the median mortality rate was 42.2%. Mortality before 2000 was 47.7% and after 2000 was 32.3% (P = .023); mortality was reduced only at 30 days after spontaneous bacterial peritonitis (49% vs 31.5%; P = .005).

CONCLUSIONS

In patients with cirrhosis, infections increase mortality 4-fold; 30% of patients die within 1 month after infection and another 30% die by 1 year. Prospective studies with prolonged follow-up evaluation and to evaluate preventative strategies are needed.

Systematic review and meta-analysis of preoperative antisepsis with chlorhexidine versus povidone–iodine in clean-contaminated surgery

Background

Surgical-site infection increases morbidity, mortality and financial burden. The preferred topical antiseptic agent (chlorhexidine or povidone–iodine) for preoperative skin cleansing is unclear.

Methods

A meta-analysis of clinical trials was conducted to determine whether preoperative antisepsis with chlorhexidine or povidone–iodine reduced surgical-site infection in clean-contaminated surgery.

Results

The systematic review identified six eligible studies, containing 5031 patients. Chlorhexidine reduced postoperative surgical-site infection compared with povidone–iodine (pooled odds ratio 0·68, 95 per cent confidence interval 0·50 to 0·94; P = 0·019).

Conclusion

Chlorhexidine should be used preferentially for preoperative antisepsis in clean-contaminated surgery.

Meta-analysis: levamisole improves the immune response to hepatitis B vaccine in dialysis patients

BACKGROUND

Patients undergoing maintenance dialysis often fail to mount protective antibodies to hepatitis B virus surface antigen (HBsAg) following vaccination against hepatitis B virus (HBV). Some authors have suggested that levamisole improves immune response to HBV vaccine in dialysis population. However, consistent information on this issue does not exist.

AIM

To evaluate efficacy and safety of levamisole as adjuvant to hepatitis B virus (HBV) vaccine in dialysis patients by performing a systematic review of the literature with a meta-analysis of clinical trials.

METHODS

We used the random-effects model of DerSimonian and Laird, with heterogeneity and sensitivity analyses. Only trials comparing the seroresponse rate in study subjects (levamisole plus HBV vaccine) vs. controls (HBV vaccine alone) were included. The end point of interest was the rate of patients showing seroprotective anti-hepatitis B titres at completion of HBV vaccine schedule in study vs. control groups.

RESULTS

We identified four studies involving 328 unique patients on regular dialysis. Only prospective, randomized clinical trials (RCTs) were included. Pooling of study results showed a significant increase in response rates among study (levamisole plus HBV vaccine) vs. control (HBV vaccine alone) patients; the pooled Odds Ratio was 2.432 (95% Confidence Intervals, 1.34; 4.403), P = 0.002. No study heterogeneity was found. These results did not change in various subgroups of interest.

CONCLUSIONS

Our meta-analysis showed that levamisole significantly improves immune response to hepatitis B vaccine in dialysis population. The limited number of patients precluded more conclusions.

PCR-single-strand conformational polymorphism method for rapid detection of rifampin-resistant Mycobacterium tuberculosis: systematic review and meta-analysis

The reference standard methods for drug susceptibility testing of Mycobacterium tuberculosis, such as culture on Lowenstein-Jensen or Middlebrook 7H10/11 medium, are very slow to give results; and due to the emergence of multidrug-resistant M. tuberculosis and extensively drug-resistant M. tuberculosis, there is an urgent demand for new, rapid, and accurate drug susceptibility testing methods. PCR-single-strand conformational polymorphism (PCR-SSCP) analysis has been proposed as a rapid method for the detection of resistance to rifampin, but its accuracy has not been systematically evaluated. We performed a systematic review and meta-analysis to evaluate the accuracy of PCR-SSCP analysis for the detection of rifampin-resistant tuberculosis. We searched the Medline, Embase, Web of Science, BIOSIS, and LILACS databases and contacted authors if additional information was required. Ten studies met our inclusion criteria for rifampin resistance detection. We applied the summary receiver operating characteristic (SROC) curve to perform the meta-analysis and to summarize diagnostic accuracy. The sensitivity of PCR-SSCP analysis for the rapid detection of rifampin-resistant tuberculosis was 0.79 (95% confidence interval [CI], 0.75 to 0.82), the specificity was 0.96 (95% CI, 0.94 to 0.98), the positive likelihood ratio was 16.10 (95% CI, 5.87 to 44.13), the negative likelihood ratio was 0.20 (95% CI, 0.10 to 0.40), and the diagnostic odds ratio was 100.93 (95% CI, 31.95 to 318.83). PCR-SSCP analysis is a sensitive and specific test for the rapid detection of rifampin-resistant M. tuberculosis. Additional studies in countries with a high prevalence of multidrug-resistant M. tuberculosis and also cost-effectiveness analysis are required in order to obtain a complete picture on the utility of this method for rapid drug resistance detection in M. tuberculosis.

Pegylated interferon monotherapy of chronic hepatitis C in dialysis patients: Meta-analysis of clinical trials

The efficacy and safety of pegylated interferon monotherapy in patients with chronic renal failure and chronic hepatitis C remains unclear, although a number of small clinical trials have been published addressing this issue. A systematic review of the literature with a meta-analysis of clinical trials was performed in order to assess efficacy and safety of initial pegylated interferon monotherapy in chronic renal failure patients with chronic hepatitis C. The primary outcome was sustained virological response (as a measure of efficacy); the secondary outcome was drop-out rate (as a measure of tolerability). The random effects model of Der Simonian and Laird was used, with heterogeneity and sensitivity analyses. Sixteen clinical trials (254 unique patients) were identified, five (31%) being controlled studies; the majority (15/16 = 94%) regarded patients on long-term dialysis. The summary estimate for sustained virological response and drop-out rate was 33% [95% Confidence Intervals (95%CI) 24-43] and 23% (95%CI, 14-33), respectively. The most frequent side-effects requiring interruption of treatment were haematological (18%) and gastrointestinal (14%). In the group of controlled clinical trials, the summary estimate for sustained viral response and drop-out rate was 38% (95% CI, 18-59), and 15% (95% CI, 3-26), respectively. The studies were heterogeneous with regard to sustained virological response and drop-out rate. Pegylated IFN does not provide an added benefit in terms of virological response in comparison with standard IFN monotherapy. Tolerance to pegylated-IFN monotherapy was unsatisfactory. Prospective trials are in progress to assess the optimal antiviral therapy for chronic hepatitis C in dialysis patients.

Short-term effects of PM10 and NO2 on respiratory health among children with asthma or asthma-like symptoms: a systematic review and meta-analysis

OBJECTIVE

Our goal was to quantify the short-term effects of particulate matter with aerodynamic diameter < or = 10 microm (PM10) and nitrogen dioxide (NO2) on respiratory health of asthmatic children from published panel studies, and to investigate the influence of study and population characteristics as effect modifiers.

DATA EXTRACTION

After a systematic literature review, we extracted quantitative estimates of the association of PM10 and/or NO2 with respiratory symptoms and peak expiratory flow (PEF). Combined effect estimates for an increase of 10 microg/m3 were calculated by random effects meta-analysis for all studies and for different strata defined by study characteristics. The effect of publication bias was investigated with Egger's and Begg's tests and "trim-and-fill" analyses.

DATA SYNTHESIS

We identified 36 studies; 14 were part of the European Pollution Effects on Asthmatic Children in Europe (PEACE) study. Adverse associations of PM10 with asthma symptoms were statistically significant [odds ratio (OR) = 1.028; 95% confidence interval (CI), 1.006-1.051]. There were also associations, although not statistically significant, of PM10 with cough (OR = 1.012; 95% CI, 0.997-1.026) and on PEF (decrease of -0.082 L/min; 95% CI, -0.214 to 0.050). NO2 had statistically significant associations with asthma symptoms in the overall analysis considering all possible lags (OR = 1.031; 95% CI, 1.001-1.062), but not when we evaluated only the 0-1 lag. We found no publication bias, although it appeared when excluding the PEACE studies. When we applied the trim-and-fill method to the data set without the PEACE studies, the results were similar to the overall estimates from all studies. There was an indication for stronger PM10 associations for studies conducted in summer, outside of Europe, with longer lags, and in locations with higher NO2 concentrations.

CONCLUSIONS

We found clear evidence of effects of PM10 on the occurrence of asthma symptom episodes, and to a lesser extent on cough and PEF. The results for NO2 are more difficult to interpret because they depend on the lag times examined. There was an indication of effect modification by several study conditions.

Reported effects in randomized controlled trials were compared with those of nonrandomized trials in cholecystectomy

OBJECTIVES

Because external validity of randomized controlled trials (RCTs) may be insufficient, the performance of nonrandomized controlled trials (nRCTs) is increasingly debated. RCTs and nRCTs were compared using the example of laparoscopic vs. open cholecystectomy (LC vs. OC).

STUDY DESIGN AND SETTING

RCTs and nRCTs comparing LC and OC were identified by searching PubMed. To assess internal and external validity of the studies, patient characteristics, relative risks, and mean differences of RCTs and nRCTs were compared by meta-analytic techniques.

RESULTS

In total, 162 studies were analyzed (136 nRCTs and 26 RCTs). Significant discrepancies between RCT- and nRCT-based results were revealed for 3 of 15 variables: overall complications (P<0.021), wound infections (P<0.014), and length of hospital stay (P<0.005). In RCTs and in nRCTs, length of hospital stay and return to work were significantly reduced when using LC compared with OC. The results of nRCTs were more often heterogeneous among themselves (11 of 15) as compared with RCTs (4 of 15).

CONCLUSION

The results of RCTs and nRCTs differ significantly in at least 20% of the variables. External validities of RCTs and nRCTs in LC vs. OC appear to be similar. Between-study heterogeneity was larger in nRCTs than in RCTs of cholecystectomy.

Meta-analysis: diagnostic value of serum anti-mutated citrullinated vimentin antibodies in patients with rheumatoid arthritis

Conventional tests are not always helpful in making a diagnosis of rheumatoid arthritis (RA). This study aimed to comprehensively and quantitatively summarize the evidence on the accuracy of anti-mutated citrullinated vimentin (MCV) assay in the diagnosis of RA. A comprehensive meta-review of data on the accuracy of MCV concentrations in the diagnosis of RA were carried out from 16 published studies. Furthermore, receiver operating characteristic curves were used to summarize the overall test performance. The summary estimates for MCV in the diagnosis of RA were: sensitivity 0.77 [95% confidence interval (CI) 0.75-0.78], specificity 0.89 (95% CI 0.87-0.90), positive likelihood ratio (LR+) 7.24 (95% CI 5.60-9.36), negative likelihood ratio (LR-) 0.28 (95% CI 0.23-0.34) and diagnostic odds ratio 29.66 (95% CI 21.09-41.71). The area under the summary receiver operating characteristic curves was 0.92. Data from meta-analysis suggest the accuracy of MCV assay in the diagnosis of RA is high, but ultimately clinician must consider the results of MCV tests combing with other conventional examinations and the clinical feature.

PTSD after deployment to Iraq: conflicting rates, conflicting claims

BACKGROUND

Post-traumatic stress disorder (PTSD) has been called one of the signature injuries of the Iraq War. In this review prevalence estimates of PTSD are summarized and discrepancies are discussed in relation to methodological differences between studies.

METHOD

We searched for population-based studies with a minimum sample size of 300. Studies based on help-seeking samples were excluded. We identified 60 possible papers, of which 19 fulfilled the inclusion criteria. Prevalence estimates and study characteristics were examined graphically with forest plots, but because of high levels of heterogeneity between studies, overall estimates of PTSD prevalence were not discussed.

RESULTS

The prevalence of PTSD in personnel deployed to Iraq varied between 1.4% and 31%. Stratifying studies by PTSD measure only slightly reduced the variability in prevalence. Anonymous surveys of line infantry units reported higher levels of PTSD compared to studies that are representative of the entire deployed population. UK studies tend to report lower prevalence of PTSD compared with many US studies; however, when comparisons are restricted to studies with random samples, prevalences are similar. US studies that have assessed personnel more than once since return from deployment have shown that PTSD prevalence increases over the 12 months following deployment.

CONCLUSIONS

Differences in methodologies and samples used should be considered when making comparisons of PTSD prevalence between studies. Further studies based on longitudinal samples are needed to understand how the prevalence of PTSD changes over time.

The association between obesity and low back pain: a meta-analysis

This meta-analysis assessed the association between overweight/obesity and low back pain. The authors systematically searched the Medline (National Library of Medicine, Bethesda, Maryland) and Embase (Elsevier, Amsterdam, the Netherlands) databases until May 2009. Ninety-five studies were reviewed and 33 included in the meta-analyses. In cross-sectional studies, obesity was associated with increased prevalence of low back pain in the past 12 months (pooled odds ratio (OR) = 1.33, 95% confidence interval (CI): 1.14, 1.54), seeking care for low back pain (OR = 1.56, 95% CI: 1.46, 1.67), and chronic low back pain (OR = 1.43, 95% CI: 1.28, 1.60). Compared with non-overweight people, overweight people had a higher prevalence of low back pain but a lower prevalence of low back pain compared with obese people. In cohort studies, only obesity was associated with increased incidence of low back pain for > or =1 day in the past 12 months (OR = 1.53, 95% CI: 1.22, 1.92). Results remained consistent after adjusting for publication bias and limiting the analyses to studies that controlled for potential confounders. Findings indicate that overweight and obesity increase the risk of low back pain. Overweight and obesity have the strongest association with seeking care for low back pain and chronic low back pain.

The association between smoking and low back pain: a meta-analysis

OBJECTIVE

To assess the association between smoking and low back pain with meta-analysis.

METHODS

We conducted a systematic search of the MEDLINE and EMBASE databases until February 2009. Eighty-one studies were reviewed and 40 (27 cross-sectional and 13 cohort) studies were included in the meta-analyses.

RESULTS

In cross-sectional studies, current smoking was associated with increased prevalence of low back pain in the past month (pooled odds ratio [OR] 1.30, 95% confidence interval [CI], 1.16-1.45), low back pain in the past 12 months (OR 1.33, 95% CI, 1.26-1.41), seeking care for low back pain (OR 1.49, 95% CI, 1.38-1.60), chronic low back pain (OR 1.79, 95% CI, 1.27-2.50) and disabling low back pain (OR 2.14, 95% CI, 1.11-4.13). Former smokers had a higher prevalence of low back pain compared with never smokers, but a lower prevalence of low back pain than current smokers. In cohort studies, both former (OR 1.32, 95% CI, 0.99-1.77) and current (OR 1.31, 95% CI, 1.11-1.55) smokers had an increased incidence of low back pain compared with never smokers. The association between current smoking and the incidence of low back pain was stronger in adolescents (OR 1.82, 95% CI, 1.42-2.33) than in adults (OR 1.16, 95% CI, 1.02-1.32).

CONCLUSIONS

Our findings indicate that both current and former smokers have a higher prevalence and incidence of low back pain than never smokers, but the association is fairly modest. The association between current smoking and the incidence of low back pain is stronger in adolescents than in adults.

Value of quantitative analysis of circulating cell free DNA as a screening tool for lung cancer: a meta-analysis

OBJECTIVE

Quantitative analysis of circulating cell free DNA is considered as a possible aid for lung cancer screening. We aimed to comprehensively review the evidence for use of circulating cell free DNA to screen for lung cancer.

METHODS

After a systematic review of English language studies, sensitivity, specificity, and other measures of accuracy of circulating DNA assay in the diagnosis of lung cancer were pooled using random-effects models. Summary receiver operating characteristic curves were used to summarize overall test performance.

RESULTS

Ten studies met our inclusion criteria. The summary estimates for quantitative analysis of circulating cell free DNA in lung cancer screening in the studies included were as follows: sensitivity, 0.80 (95% confidence interval (CI), 0.77-0.83); specificity, 0.77 (95% CI, 0.74-0.80); positive likelihood ratio, 4.54 (95% CI, 2.66-7.76); negative likelihood ratio, 0.28 (95% CI, 0.19-0.40); and diagnostic odds ratio, 20.33 (95% CI, 10.12-40.86).

CONCLUSIONS

The current evidence suggests that the diagnostic accuracy of quantitative analysis of circulating DNA is not lower than conventional serum biomarkers for lung cancer screening, at least. However, it is not recommend for lung cancer screening alone, because its discrimination power is not very perfect. The value of circulating DNA assay in combination with conventional markers for lung cancer detection deserved further investigation.

Prevention of NSAID-related upper gastrointestinal toxicity: a meta-analysis of traditional NSAIDs with gastroprotection and COX-2 inhibitors

Background:

Traditional NSAIDs (tNSAIDs) and COX-2 inhibitors (COX-2s) are important agents for the treatment of a variety or arthritic conditions. The purpose of this study was to systematically review the effectiveness of misoprostol, H2-receptor antagonists (H2RAs), and proton pump inhibitors (PPIs) for the prevention of tNSAID related upper gastrointestinal (GI) toxicity, and to review the upper gastrointestinal (GI) safety of COX-2s.

Methods:

An extensive literature search was performed to identify randomized controlled trials (RCTs) of prophylactic agents used for the prevention of upper GI toxicity, and RCTs that assessed the GI safety of the newer COX-2s. Meta-analysis was performed in accordance with accepted techniques.

Results:

39 gastroprotection and 69 COX-2 RCTs met inclusion criteria. Misoprostol, PPIs, and double doses of H2RAs are effective at reducing the risk of both endoscopic gastric and duodenal tNSAID-induced ulcers. Standard doses of H2RAs are not effective at reducing the risk of tNSAID-induced gastric ulcers, but reduce the risk of duodenal ulcers. Misoprostol is associated with greater adverse effects than the other agents, particularly at higher doses. COX-2s are associated with fewer endoscopic ulcers and clinically important ulcer complications, and have fewer treatment withdrawals due to GI symptoms than tNSAIDS. Acetylsalicylic acid appears to diminish the benefit of COX-2s over tNSAIDs. In high risk GI patients, tNSAID with a PPI or a COX-2 alone appear to offer similar GI safety, but a strategy of a COX-2 with a PPI appears to offer the greatest GI safety.

Conclusion:

Several strategies are available to reduce the risk of upper GI toxicity with tNSAIDs. The choice between these strategies needs to consider patients’ underlying GI and cardiovascular risk.

Effects of probiotics for the prevention and treatment of radiation-induced diarrhea

BACKGROUND AND AIMS

Probiotic supplementation seems to provide beneficial effects in the prevention and treatment of radiation-induced diarrhea. We performed a systematic review and meta-analysis to estimate the efficacy of probiotic supplementation for prevention and treatment of radiation-induced diarrhea.

METHODS

Two reviewers independently searched PubMed, EMBASE, Cochrane Library, Google Scholar and on-line clinical trials registers (up to January 2009) for randomized controlled trials that evaluated the efficacy of probiotic supplementation for the prevention and treatment of radiation-induced diarrhea. Each clinical trial was separately evaluated for study characteristics, methodologic quality and outcomes. Results of the randomized controlled trials were pooled in a meta-analysis.

RESULTS

Four randomized controlled trials were included. Three clinical trials, with a total of 632 subjects, evaluated the preventive effects of probiotic supplementation and 1 study evaluated the therapeutic role. Random effects meta-analysis of the preventive trials did not show significant differences between probiotic supplementation and control groups (odds ratio 0.47; 95% confidence interval: 0.13-1.67). However, the few available trials and the presence of significant clinical and statistical heterogeneity limited the analysis. Similarly, the therapeutic clinical trial did not show significant differences between active and placebo groups. No major adverse events owing to probiotic supplementation were reported in any study.

CONCLUSIONS

Probiotic supplementation showed beneficial effect in the prevention and treatment of radiation-induced diarrhea in experimental animal studies. Encouraging results have been observed in humans; however, the few available clinical studies do not allow firm conclusions. More well-performed, randomized placebo-controlled studies are needed.

Effects of walnut consumption on blood lipids and other cardiovascular risk factors: a meta-analysis and systematic review

BACKGROUND

Consumption of nuts has been associated with a decreased risk of cardiovascular disease events and death. Walnuts in particular have a unique profile: they are rich in polyunsaturated fatty acids, which may improve blood lipids and other cardiovascular disease risk factors.

OBJECTIVES

We aimed to conduct a literature review and a meta-analysis to combine the results from several trials and to estimate the effect of walnuts on blood lipids.

DESIGN

Literature databases were searched for published trials that compared a specifically walnut-enhanced diet with a control diet. We conducted a random-effects meta-analysis of weighted mean differences (WMDs) of lipid outcomes.

RESULTS

Thirteen studies representing 365 participants were included in the analysis. Diets lasted 4-24 wk with walnuts providing 10-24% of total calories. When compared with control diets, diets supplemented with walnuts resulted in a significantly greater decrease in total cholesterol and in LDL-cholesterol concentrations (total cholesterol: WMD = -10.3 mg/dL, P < 0.001; LDL cholesterol: WMD = -9.2 mg/dL, P < 0.001). HDL cholesterol and triglycerides were not significantly affected by walnut diets more than with control diets (HDL cholesterol: WMD = -0.2, P = 0.8; triglycerides: WMD = -3.9, P = 0.3). Other results reported in the trials indicated that walnuts provided significant benefits for certain antioxidant capacity and inflammatory markers and had no adverse effects on body weight [body mass index (kg/m(2)): WMD = -0.4, P = 0.5; weight (kg): WMD = -0.05, P = 0.97].

CONCLUSIONS

Overall, high-walnut-enriched diets significantly decreased total and LDL cholesterol for the duration of the short-term trials. Larger and longer-term trials are needed to address the effects of walnut consumption on cardiovascular risk and body weight.

Childhood sexual abuse and adolescent pregnancy: a meta-analytic update

OBJECTIVE

Recent increases in adolescent pregnancies have sparked a renewed impetus to identify risk factors, such as childhood sexual abuse (CSA), associated with adolescent pregnancy. Given mixed evidence regarding the strength of the relationship between CSA and adolescent pregnancy (Blinn-Pike, Berger, Dixon, Kuschel, & Kaplan, 2002), our objective was to provide an estimate of the effect size of this relationship using updated literature and meta-analytic techniques.

METHODS

Meta-analyses of 21 studies were conducted using a random effects model of binary outcomes to determine aggregate effect-size estimates controlling for study heterogeneity.

RESULTS

CSA significantly increased the odds of experiencing an adolescent pregnancy by 2.21-fold (95% CI: 1.94-2.51). A supplemental analysis suggested that 4.5 out of 10 pregnant adolescents may have a prior history of CSA.

CONCLUSIONS

CSA places females at increased risk for subsequent adolescent pregnancy. Addressing conditions associated with CSA might impact the overall adolescent pregnancy rate.

Should FEV1/FEV6 replace FEV1/FVC ratio to detect airway obstruction? A metaanalysis

BACKGROUND

The conventional FEV(1)/FVC test is the "gold standard" to quantitate airway obstruction, but elderly subjects or patients with severe respiratory diseases quite frequently cannot make such an effort. Many studies have investigated the usefulness of FEV(1)/forced expired volume in 6 s (FEV(6)) measurements as an alternative for FEV(1)/FVC for diagnosis of airway obstruction. We conducted a meta-analysis to determine the FEV(1)/FEV(6) substitute for FEV(1)/FVC in the diagnosis of airway obstruction.

METHODS

After a systematic review of all-language studies, sensitivity, specificity, and other measures of accuracy of FEV(1)/FEV(6) in the diagnosis of airway obstruction were pooled using random-effects models. Summary receiver operating characteristic curves were used to summarize overall test performance.

RESULTS

Eleven studies met our inclusion criteria. The summary estimates for FEV(1)/FEV(6) in the diagnosis of airway obstruction in the studies included were as follows: sensitivity, 0.89 (95% confidence interval [CI], 0.83 to 0.93); specificity, 0.98 (95% CI, 0.95 to 0.99); positive likelihood ratio, 45.46 (95% CI, 18.26 to 113.21); negative likelihood ratio, 0.11 (95% CI, 0.08 to 0.17); diagnostic odds ratio, 396.02 (95% CI, 167.32 to 937.31); and diagnostic score, 5.98 (95% CI, 5.12 to 6.84).

CONCLUSIONS

FEV(1)/FEV(6) is a sensitive and specific test for the diagnosis of airway obstruction. FEV(1)/FEV(6) can be used as a valid alternative for FEV(1)/FVC in the diagnosis of airway obstruction.

A systematic review of randomized controlled trials that evaluate strategies to avoid epidural vein cannulation during obstetric epidural catheter placement

BACKGROUND

In this systematic review, we evaluated the evidence for seven strategies which have been proposed to minimize the incidence of epidural vein cannulation during lumbar epidural catheter placement in pregnant women.

METHODS

Multiple databases were searched to identify prospective, randomized, controlled trials between December 1966 and October 2007 that evaluated methods to avoid epidural vein cannulation after lumbar epidural catheter placement in pregnant women. Published trials were evaluated using a quality assessment tool, and results were combined to evaluate efficacy to prevent epidural vein cannulation.

RESULTS

Of 90 trials screened, 30 trials were included (n = 12,738 subjects). Five strategies reduce the risk of epidural vein cannulation: the lateral as opposed to sitting position (six trials, mean (sd) quality score = 35% [11%], odds ratio (OR) 0.53 [95% confidence interval (CI) 0.32-0.86]), fluid administered through the epidural needle before catheter insertion (8 trials, quality score 48% [18%], OR 0.49 [95% CI 0.25-0.97]), single rather than multiorifice catheter (5 trials, quality score 30% [6%], OR 0.64 [95% CI 0.45-0.91]), a wire-embedded polyurethane compared with polyamide epidural catheter (1 trial, 31%, plus 4 unscored abstracts, OR 0.14 [95% CI 0.06-0.30]) and catheter insertion depth < or =6 cm (2 trials, 47% [11%], OR 0.27 [95% CI 0.10-0.74]). The paramedian as opposed to midline needle approach and smaller epidural needle or catheter gauges do not reduce the risk of epidural vein cannulation.

CONCLUSION

The risk of intravascular placement of a lumbar epidural catheter in pregnancy may be reduced with the lateral patient position, fluid predistension, a single orifice catheter, a wire-embedded polyurethane epidural catheter and limiting the depth of catheter insertion to 6 cm or less. In general, low manuscript quality weakens the strength of these conclusions.

Diagnostic value of the soluble triggering receptor expressed on myeloid cells-1 in bacterial infection: a meta-analysis

OBJECTIVE

To evaluate the accuracy of the soluble triggering receptor expressed on myeloid cells-1 (sTREM-1) as a diagnostic test for bacterial infection.

DESIGN

Meta-analysis of 13 diagnostic studies.

DATA SOURCE

Medline; Embase; Web of Science (from January 1966 to January, update to August 2008); and Cochrane Controlled Clinical Trials Register Database (through first quarter 2008).

MEASUREMENTS AND RESULTS

A meta-analysis of all 73 studies was performed. Thirteen studies fulfilled the inclusion criteria (980 patients, 557 patients with bacterial infection, 423 with non-bacterial infection); global prevalence was 56.8%. The global sensitivity was 0.82 (95% confidence interval CI, 0.68-0.90), the specificity was 0.86 (95% CI, 0.77-0.91), the positive likelihood ratio (PLR) was 5.66 (95% CI, 3.41-9.38), the negative likelihood ratio (NLR) was 0.21 (95% CI, 0.12-0.40), and the diagnostic odds ratio (DOR) was 26.35 (95% CI, 10.32-67.28). The area under the curve of the summary receiver operator characteristic (SROC) was 0.86 (95% CI, 0.77-0.91), with a Q point value of 0.84. The sensitivity of the sTREM-1 assay for diagnosis of urinary tract infection was low (0.18, 95% CI, 0.05-0.51).

CONCLUSIONS

sTREM-1 represents a reliable biological marker of bacterial infection, but it may be not a sufficient biological marker for infection of the urinary tract as a result of its low sensitivity. Whether sTREM-1 guidance can reduce antibiotic use as well as the measurement of sTREM-1 in different types of infection will require additional prospective studies.

Minimally invasive total hip arthroplasty: a systematic review

The purpose of this study was to compare the operative outcome between mini and standard incisions in total hip arthroplasty (THA). We identified 12 randomised or quasi-randomised control trials (RCT or qRCT) published between 1996 and 2008. Subgroup and sensitivity analyses were performed to evaluate the differences in results for surgical approach, trial quality, and follow-up duration. Operative time and blood loss were significantly reduced in the mini-incision group for studies with the posterior or posterolateral approach. Concerning postoperative complications, there were no significant differences between the two groups with no significant heterogeneity. No differences were observed between the two groups for Harris hip score and radiographic results except for cup anterversion. Although mini-incision appeared to have similar outcomes compared to standard incision, the follow-up is short-term according to current standards in THA. High-quality studies are required to compare the outcomes of these two procedures.

Antiviral therapy of hepatitis C in chronic kidney diseases: meta-analysis of controlled clinical trials

Hepatitis C virus (HCV) infection remains frequent in patients with chronic kidney disease and the detrimental role of HCV on survival is well-established in this population. Several authors have reported on efficacy and safety of antiviral therapy for hepatitis C in this polulation but there is no clear consensus on management. To evaluate efficacy and safety of antiviral therapy for hepatitis C in patients with chronic kidney disease, we performed a systematic review of the published medical literature and completed a meta-analysis of controlled clinical trials. The primary outcome was sustained virological response (as a measure of efficacy); the secondary outcome was drop-out rate (as a measure of tolerability). We used the random effects model of Der Simonian and Laird, with heterogeneity and sensitivity analyses. We identified 13 studies including 539 unique patients; 10 (76.9%) concerned patients on maintenance dialysis. Only prospective, controlled clinical trials were included. Pooling of study results showed a significant increase of viral response in study (patients treated with antiviral therapy) than control patients (patients who did not receive therapy), the pooled odds ratio (OR) of failure to obtain a sustained viral response was 0.081 [95% confidence intervals (CI), 0.029-0.230], P = 0.0001. The pooled OR of drop-out rate was significantly increased in study vs control patients, OR = 0.389 (95% CI, 0.155-0.957), P = 0.04. The studies were heterogeneous with regard to viral response and drop-out rate. In the subset of clinical trials (n = 6) involving only dialysis patients receiving interferon (IFN) monotherapy for chronic HCV, there was a significant difference in the risk of failure to obtain a sustained viral response (study vs control patients), OR = 0.054 (95% CI, 0.019; 0.150), P = 0.0001 (random-effects model). No significant (NS) heterogeneity was found (Q = 14.604, P = 1.0). No difference in the drop-out rate between study and control patients was shown, OR = 0.920 (95% CI, 0.367; 2.311), NS. This result being homogeneous (Q = 3.639, P = 0.388). Our meta-analysis showed that the viral response was greater in patients with chronic kidney disease who received antiviral therapy than controls. No difference in the drop-out rate between study and control patients occurred in the subgroup of dialysis patients on IFN monotherapy. These results support IFN-based therapy for hepatitis C in patients on maintenance dialysis.

Recent developments in meta-analysis

The art and science of meta-analysis, the combination of results from multiple independent studies, is now more than a century old. In the last 30 years, however, as the need for medical research and clinical practice to be based on the totality of relevant and sound evidence has been increasingly recognized, the impact of meta-analysis has grown enormously. In this paper, we review highlights of recent developments in meta-analysis in medical research. We outline in particular how emphasis has been placed on (i) heterogeneity and random-effects analyses; (ii) special consideration in different areas of application; (iii) assessing bias within and across studies; and (iv) extension of ideas to complex evidence synthesis. We conclude the paper with some remarks on ongoing challenges and possible directions for the future.

Diagnostic value of carcinoembryonic antigen in malignant pleural effusion: a meta-analysis

BACKGROUND AND OBJECTIVE

Conventional tests are not always helpful in making a diagnosis of malignant pleural effusion (MPE). Many studies have investigated the utility of pleural carcinoembryonic antigen (CEA) in the early diagnosis of MPE. The present meta-analysis determined the accuracy of CEA measurement in the diagnosis of MPE.

METHODS

A systematic review of English language studies was conducted and data on the accuracy of pleural CEA concentrations in the diagnosis of MPE were pooled using random effects models. Receiver operating characteristic curves were used to summarize the overall test performance.

RESULTS

Forty-five studies met the inclusion criteria for the meta-analysis. The summary estimates for CEA in the diagnosis of MPE were: sensitivity 0.54 (95% CI: 0.52-0.55), specificity 0.94 (95% CI: 0.93-0.95), positive likelihood ratio 9.52 (95% CI: 6.97-13.01), negative likelihood ratio 0.49 (95% CI: 0.44-0.54) and diagnostic odds ratio 22.5 (95% CI: 15.6-32.5). Analysis of a subset of 11 studies which examined the value of pleural CEA in ruling out a diagnosis of malignant mesothelioma found that the sensitivity and specificity of a CEA level exceeding cut-off values were 0.97 (95% CI: 0.93-0.99) and 0.60 (95% CI: 0.55-0.65), respectively.

CONCLUSIONS

Measurement of pleural CEA is likely to be a useful diagnostic tool for confirming MPE, and is also helpful in the differential diagnosis between malignant pleural mesothelioma and metastatic lung cancer. The results of CEA assays should be interpreted in parallel with clinical findings and the results of conventional tests.

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

BACKGROUND

Several approaches are available for evaluating heterogeneity in meta-analysis. Sensitivity analyses are often used, but these are often implemented in various non-standardized ways.

METHODS

We developed and implemented sequential and combinatorial algorithms that evaluate the change in between-study heterogeneity as one or more studies are excluded from the calculations. The algorithms exclude studies aiming to achieve either the maximum or the minimum final I(2) below a desired pre-set threshold. We applied these algorithms in databases of meta-analyses of binary outcome and >/=4 studies from Cochrane Database of Systematic Reviews (Issue 4, 2005, n = 1011) and meta-analyses of genetic associations (n = 50). Two I(2) thresholds were used (50% and 25%).

RESULTS

Both algorithms have succeeded in achieving the pre-specified final I(2) thresholds. Differences in the number of excluded studies varied from 0% to 6% depending on the database and the heterogeneity threshold, while it was common to exclude different specific studies. Among meta-analyses with initial I(2) > 50%, in the large majority [19 (90.5%) and 208 (85.9%) in genetic and Cochrane meta-analyses, respectively] exclusion of one or two studies sufficed to decrease I(2) < 50%. Similarly, among meta-analyses with initial I(2) > 25%, in most cases [16 (57.1%) and 382 (81.3%), respectively) exclusion of one or two studies sufficed to decrease heterogeneity even <25%. The number of excluded studies correlated modestly with initial estimated I(2) (correlation coefficients 0.52-0.68 depending on algorithm used).

CONCLUSIONS

The proposed algorithms can be routinely applied in meta-analyses as standardized sensitivity analyses for heterogeneity. Caution is needed evaluating post hoc which specific studies are responsible for the heterogeneity.

Practical methodology of meta-analysis of individual patient data using a survival outcome

Meta-analysis of individual patient data (MIPD) is considered as one of the statistical approaches to provide integrated information on the effect of a treatment or an intervention. Statistical analysis of such meta-analyses should account for the clustered structure of data which is induced by all factors varying across the trials. For survival analysis, several models can handle such clustering under proportional hazards. This comprises models with fixed or random trial effects, stratified models and marginal models. In this paper, we review these models and compare their performances using a numerical simulation study. Results show that frailty models, and particularly those with random treatment by trial interactions, are well suited for meta-analyses on individual patient data. This is further exemplified on a meta-analysis of three trials comparing high-dose therapy to conventional chemotherapy in multiple myeloma.

Interferon monotherapy of chronic hepatitis C in dialysis patients: meta-analysis of clinical trials

The efficacy of monotherapy with interferon (IFN) (conventional or pegylated IFN) in dialysis patients with chronic hepatitis C remains unclear, although a number of clinical trials have been published addressing this issue. The aim of the study was to evaluate the efficacy and safety of monotherapy by conventional or pegylated IFN in dialysis patients with chronic hepatitis C by performing a systematic review of the literature with a meta-analysis of clinical trials. The primary outcome was sustained virological response (SVR; as a measure of efficacy), and the secondary outcome was drop-out rate (as a measure of tolerability). We used the random-effects model of Der Simonian and Laird, with heterogeneity and sensitivity analyses. We identified 28 clinical trials (645 unique patients), of which six (21.4%) had a controlled design. In the group of trials based on conventional IFN, the summary estimate for SVR and drop-out rate was 39% [95% confidence interval (CI) 32-46] and 19% (95% CI 13-26) respectively. The summary estimate for SVR rate in patients with the hepatitis C virus genotype 1 was 33% (95% CI 19-47). In the subset of trials using pegylated IFN, the summary estimate for SVR and drop-out rate was 31% (95% CI 7-55) and 27% (95% CI 1-52) respectively. The most frequent side-effects requiring interruption of treatment were flu-like symptoms, and gastrointestinal and haematological changes. A relationship between age and drop-out rate was found, even if no statistical significance was reached (P = 0.064). The studies were heterogeneous with regard to SVR and drop-out rate. No publication bias was observed. One-third of dialysis patients with chronic hepatitis C were successfully treated with conventional or pegylated IFN monotherapy. Preliminary evidence does not support additional benefit due to monotherapy with pegylated IFN on the viral response in the chronic kidney disease (CKD) population. Tolerance to IFN monotherapy was unsatisfactory, particularly to pegylated IFN. The optimal antiviral treatment of chronic hepatitis C in dialysis populations is currently under active investigation.