[Show abstract][Hide abstract] ABSTRACT: To assess the usefulness of transcranial Doppler CO2 reactivity (CO2R) for prediction of ipsilateral ischemic stroke in carotid artery stenosis and occlusion with a meta-analysis of prospective studies based on individual patient data.
[Show abstract][Hide abstract] ABSTRACT: Non-steroidal antiandrogens and castration are the main therapy options for advanced stages of prostate cancer. However, debate regarding the value of these treatment options continues.
[Show abstract][Hide abstract] ABSTRACT: Since the influential study by van Tinteren et al. published in The Lancet in 2002, there have been an increasing number of diagnostic randomized controlled trials (RCTs) investigating the benefit of PET. If they provide valid and useful information on the benefit, these studies can play an important role in informing guideline developers and policy makers. Our aim was to investigate how far the nuclear medicine community has come on its way from accuracy studies to RCTs and which issues we have to take into account in planning future studies.
Journal of nuclear medicine : official publication, Society of Nuclear Medicine. 06/2014;
[Show abstract][Hide abstract] ABSTRACT: Recent research indicates a high recall in Google Scholar searches for systematic reviews. These reports raised high expectations of Google Scholar as a unified and easy to use search interface. However, studies on the coverage of Google Scholar rarely used the search interface in a realistic approach but instead merely checked for the existence of gold standard references. In addition, the severe limitations of the Google Search interface must be taken into consideration when comparing with professional literature retrieval tools.The objectives of this work are to measure the relative recall and precision of searches with Google Scholar under conditions which are derived from structured search procedures conventional in scientific literature retrieval; and to provide an overview of current advantages and disadvantages of the Google Scholar search interface in scientific literature retrieval.
General and MEDLINE-specific search strategies were retrieved from 14 Cochrane systematic reviews. Cochrane systematic review search strategies were translated to Google Scholar search expression as good as possible under consideration of the original search semantics. The references of the included studies from the Cochrane reviews were checked for their inclusion in the result sets of the Google Scholar searches. Relative recall and precision were calculated.
We investigated Cochrane reviews with a number of included references between 11 and 70 with a total of 396 references. The Google Scholar searches resulted in sets between 4,320 and 67,800 and a total of 291,190 hits. The relative recall of the Google Scholar searches had a minimum of 76.2% and a maximum of 100% (7 searches). The precision of the Google Scholar searches had a minimum of 0.05% and a maximum of 0.92%. The overall relative recall for all searches was 92.9%, the overall precision was 0.13%.
The reported relative recall must be interpreted with care. It is a quality indicator of Google Scholar confined to an experimental setting which is unavailable in systematic retrieval due to the severe limitations of the Google Scholar search interface. Currently, Google Scholar does not provide necessary elements for systematic scientific literature retrieval such as tools for incremental query optimization, export of a large number of references, a visual search builder or a history function. Google Scholar is not ready as a professional searching tool for tasks where structured retrieval methodology is necessary.
BMC Medical Research Methodology 10/2013; 13(1):131. · 2.21 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Although neoadjuvant radiotherapy may improve local control of rectal cancer, its clinical value requires further evaluation as a result of potential side effects and advances in surgical technique. A meta-analysis was performed to assess effectiveness and safety of neoadjuvant radiotherapy in the management of rectal cancer.
The following databases were searched: the Cochrane Library, Biosis, Web of Science, Embase, ASCO Abstracts and WHO International Clinical Trials Registry Platform. Randomized controlled trials on the following comparisons were included: (1) neoadjuvant therapy versus surgery alone and (2) neoadjuvant chemoradiotherapy versus neoadjuvant radiotherapy.
We identified 17 and 5 relevant trials that enrolled 8,568 and 2,393 patients, respectively. Neoadjuvant radiotherapy improved local control (hazard ratio 0.59; 95 % confidence interval 0.48-0.72) compared to surgery alone even after total mesorectal excision, whereas its benefit in overall survival just failed to reach statistical significance (0.93; 0.85-1.00). However, it was associated with increased perioperative mortality (1.48; 1.08-2.03), in particular if a dose of 5 Gy per fraction was administered (1.85; 1.23-2.78). Chemoradiotherapy improved local control as opposed to radiotherapy (0.53; 0.39-0.72), with no impact on perioperative outcome and long-term survival.
Neoadjuvant radiotherapy improves local control in patients with rectal cancer, particularly when chemoradiotherapy is administered. The question if the use of more effective chemotherapy protocols improves overall survival warrants further investigation.
Annals of Surgical Oncology 09/2013; · 4.12 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Evidence mapping is an increasingly popular approach to systematically evaluate published research. While there are methodological standards for systematic reviews, discrepancies exist between the terminology and methods used within evidence mapping.
The aim of this systematic review is to describe the methodology and terminology used in evidence mapping and to demonstrate the continuum between evidence mapping and traditional systematic reviews.
A systematic literature search was conducted in 10 databases in order to obtain a comprehensive picture of the state of the research standards for evidence mapping. In addition, websites of institutions which are already conducting evidence mapping were searched.
The included study pool (n = 12) shows that the terms 'evidence map' and 'scoping review' are widely used within evidence mapping. Evidence maps are an approach to depict both the number and characteristics of studies in tabular form that exist as well as evidence gaps based on primary studies and systematic reviews of broad clinical questions. Scoping reviews also summarize the literature in a tabular form but also give a descriptive narrative summary of the results. A quality assessment of the studies is generally not included.
Evidence mapping allows the identification of research gaps. This aspect is particularly important for interventions which are used without sufficient evidence. In contrast, systematic reviews are mainly used to estimate effects for interventions and evaluate whether the included studies are reliable.
[Show abstract][Hide abstract] ABSTRACT: Health professionals and policymakers aspire to make healthcare decisions based on the entire relevant research evidence. This, however, can rarely be achieved because a considerable amount of research findings are not published, especially in case of 'negative' results - a phenomenon widely recognized as publication bias. Different methods of detecting, quantifying and adjusting for publication bias in meta-analyses have been described in the literature, such as graphical approaches and formal statistical tests to detect publication bias, and statistical approaches to modify effect sizes to adjust a pooled estimate when the presence of publication bias is suspected. An up-to-date systematic review of the existing methods is lacking.Methods/design: The objectives of this systematic review are as follows:[bullet] To systematically review methodological articles which focus on non-publication of studies and to describe methods of detecting and/or quantifying and/or adjusting for publication bias in meta-analyses.[bullet] To appraise strengths and weaknesses of methods, the resources they require, and the conditions under which the method could be used, based on findings of included studies.We will systematically search Web of Science, Medline, and the Cochrane Library for methodological articles that describe at least one method of detecting and/or quantifying and/or adjusting for publication bias in meta-analyses. A dedicated data extraction form is developed and pilot-tested. Working in teams of two, we will independently extract relevant information from each eligible article. As this will be a qualitative systematic review, data reporting will involve a descriptive summary.
Results are expected to be publicly available in mid 2013. This systematic review together with the results of other systematic reviews of the OPEN project (To Overcome Failure to Publish Negative Findings) will serve as a basis for the development of future policies and guidelines regarding the assessment and handling of publication bias in meta-analyses.
[Show abstract][Hide abstract] ABSTRACT: BACKGROUND: Selective publication of studies, which is commonly called publication bias, is widely recognized. Over the years a new nomenclature for other types of bias related to non-publication or distortion related to the dissemination of research findings has been developed. However, several of these different biases are often still summarized by the term 'publication bias'. METHODS: As part of the OPEN Project (To Overcome failure to Publish nEgative fiNdings) we will conduct a systematic review with the following objectives:- To systematically review highly cited articles that focus on non-publication of studies and to present the various definitions of biases related to the dissemination of research findings contained in the articles identified.- To develop and discuss a new framework on nomenclature of various aspects of distortion in the dissemination process that leads to public availability of research findings in an international group of experts in the context of the OPEN Project.We will systematically search Web of Knowledge for highly cited articles that provide a definition of biases related to the dissemination of research findings. A specifically designed data extraction form will be developed and pilot-tested. Working in teams of two, we will independently extract relevant information from each eligible article.For the development of a new framework we will construct an initial table listing different levels and different hazards en route to making research findings public. An international group of experts will iteratively review the table and reflect on its content until no new insights emerge and consensus has been reached. DISCUSSION: Results are expected to be publicly available in mid-2013. This systematic review together with the results of other systematic reviews of the OPEN project will serve as a basis for the development of future policies and guidelines regarding the assessment and prevention of publication bias.
[Show abstract][Hide abstract] ABSTRACT: BACKGROUND: Meta-analyses are particularly vulnerable to the effects of publication bias. Despite methodologists' best efforts to locate all evidence for a given topic the most comprehensive searches are likely to miss unpublished studies and studies that are published in the gray literature only. If the results of the missing studies differ systematically from the published ones, a meta-analysis will be biased with an inaccurate assessment of the intervention's effects.As part of the OPEN project (www.open-project.eu) we will conduct a systematic review with the following objectives:[black small square] To assess the impact of studies that are not published or published in the gray literature on pooled effect estimates in meta-analyses (quantitative measure)[black small square] To assess whether the inclusion of unpublished studies or studies published in the gray literature leads to different conclusions in meta-analyses (qualitative measure) METHODS: Inclusion criteria: Methodological research projects of a cohort of meta-analyses (, which compare the effect of the inclusion or exclusion of unpublished studies or studies published in the gray literature.Literature search: To identify relevant research projects we will conduct electronic searches in Medline, Embase and The Cochrane Library; check reference lists; and contact experts.Outcomes: 1) The extent to which the effect estimate in a meta-analyses changes with the inclusion or exclusion of studies that were not published or published in the gray literature; and 2) the extent to which the inclusion of unpublished studies impacts the meta-analyses' conclusions.Data collection: Information will be collected on the area of health care; the number of meta-analyses included in the methodological research project; the number of studies included in the meta-analyses; the number of study participants; the number and type of unpublished studies; studies published in the gray literature and published studies; the sources used to retrieve studies that are unpublished, published in the gray literature, or commercially published; and the validity of the methodological research project.Data synthesis: Data synthesis will involve descriptive and statistical summaries of the findings of the included methodological research projects. DISCUSSION: Results are expected to be publicly available in the middle of 2013.
[Show abstract][Hide abstract] ABSTRACT: BACKGROUND: Systematic reviews and meta-analyses of pre-clinical studies, in vivo animal experiments in particular, can influence clinical care. Publication bias is one of the major threats of validity in systematic reviews and meta-analyses. Previous empirical studies suggested that systematic reviews and meta-analyses have become more prevalent until 2010 and found evidence for compromised methodological rigor with a trend towards improvement. We aim to comprehensively summarize and update the evidence base on systematic reviews and meta-analyses of animal studies, their methodological quality and assessment of publication bias in particular. METHODS: The objectives of this systematic review are as follows:To investigate the epidemiology of published systematic reviews of animal studies until present.To examine methodological features of systematic reviews and meta-analyses of animal studies with special attention to the assessment of publication bias.To investigate the influence of systematic reviews of animal studies on clinical research by examining citations of the systematic reviews by clinical studies.Eligible studies for this systematic review constitute systematic reviews and meta-analyses that summarize in vivo animal experiments with the purpose of reviewing animal evidence to inform human health. We will exclude genome-wide association studies and animal experiments with the main purpose to learn more about fundamental biology, physical functioning or behavior.In addition to the inclusion of systematic reviews and meta-analyses identified by other empirical studies, we will systematically search Ovid Medline, Embase, ToxNet, and ScienceDirect from 2009 to January 2013 for further eligible studies without language restrictions.Two reviewers working independently will assess titles, abstracts, and full texts for eligibility and extract relevant data from included studies. Data reporting will involve a descriptive summary of meta-analyses and systematic reviews. DISCUSSION: Results are expected to be publicly available later in 2013 and may form the basis for recommendations to improve the quality of systematic reviews and meta-analyses of animal studies and their use with respect to clinical care.
[Show abstract][Hide abstract] ABSTRACT: BACKGROUND: There is currently no consensus regarding the optimal timing for androgen suppression therapy in patients with prostate cancer that have undergone local therapy with curative intent but are proven to have node-positive disease without signs of distant metastases at the time of local therapy. The objective of this systematic review was to determine the benefits and harms of early (at the time of local therapy) versus deferred (at the time of clinical disease progression) androgen suppression therapy for patients with node-positive prostate cancer after local therapy. METHODS: The protocol was registered prospectively (CRD42011001221; http://www.crd.york.ac.uk/PROSPERO). We searched the MEDLINE, EMBASE, and CENTRAL databases, as well as reference lists, the abstracts of three major conferences, and three trial registers, to identify randomized controlled trials (search update 04/08/2012). Two authors independently screened the identified articles, assessed trial quality, and extracted data. RESULTS: Four studies including 398 patients were identified for inclusion. Early androgen suppression therapy lead to a significant decrease in overall mortality (HR 0.62, 95% CI 0.46-0.84), cancer-specific mortality (HR 0.34, 95% CI 0.18-0.64), and clinical progression at 3 or 9 years (RR 0.29, 95% CI 0.16-0.52 at 3 years and RR 0.49, 95% CI 0.36-0.67 at 9 years). One study showed an increase of adverse effects with early androgen suppression therapy. All trials had substantial methodological limitations. CONCLUSIONS: The data available suggest an improvement in survival and delayed disease progression but increased adverse events for patients with node-positive prostate cancer after local therapy treated with early androgen suppression therapy versus deferred androgen suppression therapy. However, quality of data is very low. Randomized controlled trials with blinding of outcome assessment, planned to determine the timing of androgen suppression therapy in node-positive prostate cancer using modern diagnostic imaging modalities, biochemical testing, and standardized follow-up schedules should be conducted to confirm these findings.
BMC Cancer 03/2013; 13(1):131. · 3.33 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: BACKGROUND: Methodological research has found that non-published studies often have different results than those that are published, a phenomenon known as publication bias. When results are not published, or are published selectively based on the direction or the strength of the findings, healthcare professionals and consumers of healthcare cannot base their decision-making on the full body of current evidence. METHODS: As part of the OPEN project (www.open-project.eu) we will conduct a systematic review with the following objectives:1.To determine the proportion and/or rate of non-publication of studies by systematically reviewing methodological research projects that followed up a cohort of studies thata.received research ethics committee (REC) approval,b.were registered in trial registries, orc.were presented as abstracts at conferences.2.To assess the association of study characteristics (for example, direction and/or strength of findings) with likelihood of full publication.To identify reports of relevant methodological research projects we will conduct electronic database searches, check reference lists, and contact experts. Published and unpublished projects will be included. The inclusion criteria are as follows:a.RECs: methodological research projects that examined the subsequent proportion and/or rate of publication of studies that received approval from RECs;b.Trial registries: methodological research projects that examine the subsequent proportion and/or rate of publication of studies registered in trial registries;c.Conference abstracts: methodological research projects that examine the subsequent proportion and/or rate of full publication of studies which were initially presented at conferences as abstracts.Primary outcomes: Proportion/rate of published studies; time to full publication (mean/median; cumulative publication rate by time).Secondary outcomes: Association of study characteristics with full publication.The different questions (a, b, and c) will be investigated separately. Data synthesis will involve a combination of descriptive and statistical summaries of the included methodological research projects. DISCUSSION: Results are expected to be publicly available in mid 2013.
[Show abstract][Hide abstract] ABSTRACT: To quantitatively describe (1) differences between search results derived at consecutive time points with the PubMed and OvidSP literature search interfaces over a five day interval, and (2) the migration of citations through different subsets to estimate the timeliness of OvidSP.
PubMed-Identifiers (PMIDs) of the following subsets were retrieved from PubMed and OvidSP simultaneously (within 8 h) at 11 days in March and April 2010 including 5 consecutive days: as supplied by publisher, in process, PubMed not MEDLINE, and OLDMEDLINE. Search results were compared for difference and intersection sets. The migration of citations on individual level was determined by comparison of corresponding sets over several days.
The "in process" set was stable with about 446,000 - 452,000 citations; a small fraction of up to 3 % of the total subsets were in PubMed only and OvidSP only subsets. About 96 % of the ca. 10,500 citations in the OvidSP only subset migrated within 2 days out of the "in process" subset. The database of OvidSP is updated within a period of two days.
Studies in health technology and informatics 01/2013; 192:1196.
[Show abstract][Hide abstract] ABSTRACT: Evidence Mapping ist ein neuer Ansatz zur systematischen Evidenzaufbereitung. Während Standards für die Methodik systematischer Übersichtsarbeiten vorliegen, findet man in der Literatur oft Unstimmigkeiten zur Definition und zur Vorgehensweise beim Evidence Mapping.Ziel der vorliegenden systematischen Übersicht ist es, die Methodik und Begrifflichkeiten, die beim Evidence Mapping zum Einsatz kommen, zu definieren und es von der klassischen systematischen Übersichtsarbeit abzugrenzen.Um ein vollständiges Bild des Forschungsstands zum Evidence Mapping zu gewinnen, wurde eine systematische Literaturrecherche in 10 Datenbanken durchgeführt. Außerdem wurden Webseiten von Instituten, die sich mit dieser Methodik der Evidenzaufbereitung beschäftigen, durchsucht.Der eingeschlossene Studienpool (n = 12) zeigt, dass innerhalb des Evidence Mappings die Begrifflichkeiten ,,Evidence Map“ und ,,Scoping Review“ Anwendung finden. Evidence Maps stellen dabei einen Ansatz dar, um vorhandene oder auch fehlende Evidenz auf Grundlage von Primärstudien und systematischen Übersichtsarbeiten für breite medizinische Fragestellungen in ihrer Quantität und ihren Studiencharakteristika systematisch in Tabellenform abzubilden. Scoping Reviews liefern zudem eine deskriptive Zusammenfassung der Literatur. Eine Qualitätsbewertung der Studien erfolgt dabei nicht.Evidence Mapping erlaubt durch die quantitative Darstellung der vorhandenen Forschung das Erkennen von Lücken im Wissenspool. Dieser Aspekt ist vor allem für Interventionen wichtig, die ohne ausreichende Evidenzbasis eingesetzt werden. Systematische Übersichtsarbeiten ermöglichen es hingegen einzuschätzen, welche Effekte durch Interventionen zu erwarten sind und ob das dazu vorhandene Wissen zuverlässig ist.
[Show abstract][Hide abstract] ABSTRACT: Thalassemia is a hereditary anaemia due to ineffective erythropoiesis. In particular, people with thalassaemia major develop secondary iron overload resulting from regular red blood cell transfusion. Iron chelation therapy is needed to prevent long-term complications.Both deferoxamine and deferiprone have been found to be efficacious. However, a systematic review of the effectiveness and safety of the new oral chelator deferasirox in people with thalassaemia is needed.
To assess the effectiveness and safety of oral deferasirox in people with thalassaemia and secondary iron overload.
We searched the Cystic Fibrosis and Genetic Disorders Group's Haemoglobinopathies Trials Register. We also searched MEDLINE, EMBASE, EBMR, Biosis Previews, Web of Science, Derwent Drug File, XTOXLINE and three trial registries: www.controlled-trials.com; www.clinicaltrials.gov; www.who.int./ictrp/en/. Date of the most recent searches of these databases: 24 June 2010.Date of the most recent search of the Group's Haemoglobinopathies Trials Register: 03 November 2011.
Randomised controlled trials comparing deferasirox with no therapy or placebo or with another iron chelating treatment.
Two authors independently assessed risk of bias and extracted data. We contacted study authors for additional information.
Four studies met the inclusion criteria.Two studies compared deferasirox to placebo or standard therapy of deferoxamine (n = 47). The placebo-controlled studies, a pharmacokinetic and a dose escalation study, showed that deferasirox leads to net iron excretion in transfusion-dependent thalassaemia patients. In these studies, safety was acceptable and further investigation in phase II and phase III trials was warranted.Two studies, one phase II study (n = 71) and one phase III study (n = 586) compared deferasirox to standard treatment with deferoxamine. Data suggest that a similar efficacy can be achieved depending on the ratio of doses of deferoxamine and deferasirox being compared; in the phase III trial, similar or superior efficacy for surrogate parameters of ferritin and liver iron concentration could only be achieved in the highly iron-overloaded subgroup at a mean ratio of 1 mg of deferasirox to 1.8 mg of deferoxamine corresponding to a mean dose of 28.2 mg/d and 51.6 mg/d respectively. Data on safety at the presumably required doses for effective chelation therapy are limited. Patient satisfaction was significantly better with deferasirox, while rate of discontinuations was similar for both drugs.
Deferasirox offers an important alternative line of treatment for people with thalassaemia and secondary iron overload. Based on the available data, deferasirox does not seem to be superior to deferoxamine at the usually recommended ratio of 1 mg of deferasirox to 2 mg of deferoxamine. However, similar efficacy seems to be achievable depending on the dose and ratio of deferasirox compared to deferoxamine. Whether this will result in similar efficacy in the long run and will translate to similar benefits as has been shown for deferoxamine, needs to be confirmed. Data on safety, particularly on rare toxicities and long-term safety, are still limited.Therefore, we think that deferasirox should be offered as an alternative to all patients with thalassaemia who either show intolerance to deferoxamine or poor compliance with deferoxamine. In our opinion, data are still too limited to support the general recommendation of deferasirox as first-line treatment instead of deferoxamine. If a strong preference for deferasirox is expressed, it could be offered as first-line option to individual patients after a detailed discussion of the potential benefits and risks.
[Show abstract][Hide abstract] ABSTRACT: Up to 25% of patients with node-negative colorectal cancer (CRC) on conventional histopathologic analysis ultimately die of recurrent disease. We performed a systematic review with meta-analyses to clarify whether molecular detection of isolated tumor cells or micrometastases in regional lymph nodes indicates high risk of disease recurrence and poor survival in node-negative CRC.
The following databases were searched in August 2011 to identify studies on the prognostic significance of molecular tumor-cell detection in regional lymph nodes of node-negative CRC: MEDLINE, BIOSIS, Science Citation Index, EMBASE, CCMed, and publisher databases. We extracted hazard ratios (HRs) and associated 95% CIs from the identified studies and performed random-effects model meta-analyses on overall survival, disease-specific survival, and disease-free survival.
A total of 39 studies with a cumulative sample size of 4,087 patients were included. Immunohistochemistry, reverse transcriptase polymerase chain reaction, and both techniques were applied in 30, seven, and two studies, respectively. Thirteen studies were graded with low risk of bias. Meta-analyses revealed that molecular tumor-cell detection in regional lymph nodes was associated with poor overall survival (HR, 2.20; 95% CI, 1.43 to 3.40), disease-specific survival (HR, 3.37; 95% CI, 2.31 to 4.93), and disease-free survival (HR, 2.24; 95% CI, 1.57-3.20). Subgroup analyses showed the prognostic significance of molecular tumor-cell detection of being independent of the applied detection method, molecular target, and number of retrieved lymph nodes.
Molecular detection of occult disease in regional lymph nodes is associated with an increased risk of disease recurrence and poor survival in patients with node-negative CRC.
Journal of Clinical Oncology 11/2011; 30(1):60-70. · 18.04 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Capture-recapture methods were proposed to evaluate the comprehensiveness of systematic literature searches. We investigate the statistical feasibility of capture-recapture techniques with model selection for estimating the number of missing references in literature searches using two systematic reviews in gastroenterology and hematology.
First, we compared manually selected Poisson regression models that differ with respect to included interactions. Secondly, we performed selection via componentwise boosting, which provides automatic variable selection. The proposed boosting technique is a regularized, stepwise procedure allowing to distinguish between mandatory and optional variables. Results from all models were compared based on Akaike's Information Criterion and the Bayesian Information Criterion.
For the first example, the best manually selected model suggested a number of 82 missing articles (95% CI: 52-128), whereas the boosting technique provided 127 (95% CI: 86-186) missing articles. For the second example, 140 (95% CI: 116-168) missing articles were estimated for the manually selected and 188 (95% CI: 159-223) for the automatically selected model.
Capture-recapture analysis requires the selection of an appropriate model. Because of problems of variable selection and overfitting, manual model selection yielded large estimates, varying markedly, with broad confidence intervals. By contrast, boosting was robust against overfitting and automatically created an appropriate model for inference.
Journal of clinical epidemiology 06/2011; 64(12):1364-72. · 5.48 Impact Factor