Reporting guidelines on how to write a complete and transparent abstract for overviews of systematic reviews of health care interventions

The reporting completeness and transparency of systematic reviews of prognostic prediction models for COVID-19 was poor: a methodological overview of systematic reviews

OBJECTIVES

To conduct a methodological overview of reviews to evaluate the reporting completeness and transparency of systematic reviews (SRs) of prognostic prediction models (PPMs) for COVID-19.

STUDY DESIGN AND SETTING

MEDLINE, Scopus, Cochrane Database of Systematic Reviews, and Epistemonikos (epistemonikos.org) were searched for SRs of PPMs for COVID-19 until December 31, 2022. The risk of bias in systematic reviews tool was used to assess the risk of bias. The protocol for this overview was uploaded in the Open Science Framework (https://osf.io/7y94c).

RESULTS

Ten SRs were retrieved; none of them synthesized the results in a meta-analysis. For most of the studies, there was absence of a predefined protocol and missing information on study selection, data collection process, and reporting of primary studies and models included, while only one SR had its data publicly available. In addition, for the majority of the SRs, the overall risk of bias was judged as being high. The overall corrected covered area was 6.3% showing a small amount of overlapping among the SRs.

CONCLUSION

The reporting completeness and transparency of SRs of PPMs for COVID-19 was poor. Guidance is urgently required, with increased awareness and education of minimum reporting standards and quality criteria. Specific focus is needed in predefined protocol, information on study selection and data collection process, and in the reporting of findings to improve the quality of SRs of PPMs for COVID-19.

An overview of systematic reviews on imaging tests for diagnosis of pulmonary embolism applying different network meta-analytic methods

PURPOSE

This study aimed to apply different methods of diagnostic test accuracy network meta-analysis (DTA-NMA) for studies reporting results of five imaging tests for the diagnosis of suspected pulmonary embolism (PE): pulmonary angiography (PA), computed tomography angiography (CTPA), magnetic resonance angiography (MRA), planar ventilation/perfusion (V/Q) scintigraphy and single-photon emission computed tomography ventilation/perfusion (SPECT V/Q).

METHODS

We searched four databases (MEDLINE [via PubMed], Cochrane CENTRAL, Scopus, and Epistemonikos) from inception until June 2, 2022 to identify systematic reviews (SRs) describing diagnostic accuracy of PA, CTPA, MRA, V/Q scan and SPECT V/Q for suspected PE. Study-level data were extracted and pooled using a hierarchical summary receiver operating characteristic (HSROC) meta-regression approach and two DTA-NMA models to compare accuracy estimates of different imaging tests. Risk of bias was assessed using the QUADAS-2 (Quality Assessment of Diagnostic Accuracy Studies-2) tool and certainty of evidence using the GRADE (Grading of Recommendations Assessment, Development and Evaluation) framework.

RESULTS

We identified 13 SRs, synthesizing data from 33 primary studies and for four imaging tests (PA, CTPA, MRA and V/Q scan). The HSROC meta-regression model using PA as the reference standard showed that MRA had the best overall diagnostic performance with sensitivity of 0.93 (95% confidence interval [CI]: 0.76, 1.00) and specificity of 0.94 (95% CI: 0.84, 0.99). However, DTA-NMA models indicated that V/Q scan had the highest sensitivity, while CTPA was most specific.

CONCLUSION

Selecting a different DTA-NMA method to assess multiple diagnostic tests can affect estimates of diagnostic accuracy. There is no established method, but the choice depends on the data and familiarity with Bayesian statistics.

Global prevalence of perinatal depression and anxiety during the COVID-19 pandemic: An umbrella review and meta-analytic synthesis

INTRODUCTION

The prevalence of depression and anxiety symptoms in pregnant and postpartum women during the COVID-19 pandemic was assessed by several systematic reviews (SRs) and meta-analyses which provided contrasting and different results. We aimed to summarize the evidence relating to the global prevalence of anxiety and depression among pregnant and postpartum women during the COVID-19 pandemic.

MATERIAL AND METHODS

An umbrella review of SRs and meta-analyses was performed. Searches were conducted in electronic databases up to April 2023. SRs and meta-analyses reporting the prevalence of perinatal anxiety and depression during the COVID-19 pandemic were selected for eligibility. Primary studies extracted from eligible meta-analyses were included in the quantitative synthesis. The research protocol was registered on PROSPERO (CRD42020173125).

RESULTS

A total of 25 SRs (198 primary studies) and 12 meta-analyses (129 primary studies) were included in the qualitative and quantitative synthesis, respectively. Studies involved data from five continents and 45 countries. The pooled prevalence of antenatal and postpartum depression was 29% (n = 55; 95% CI: 25%-33%) and 26% (n = 54; 95% CI: 23%-30%), respectively. In the case of anxiety, the pooled antenatal and postnatal prevalence was 31% (n = 44; 95% CI: 26%-37%; n = 16; 95% CI: 24%-39%). Differences emerged between continents, with Africa having the highest prevalence of perinatal depression and Oceania and Europe having the highest prevalence of antenatal and postnatal anxiety. The prevalence also varied depending on the assessment tools, especially for antenatal anxiety. A medium-high quality of the studies was observed. One SR assessed strength-of-evidence, reporting very low strength.

CONCLUSIONS

During the COVID-19 pandemic, depression and anxiety were common, affecting almost one in three perinatal women globally. A high heterogeneity and a risk of publication bias were found, partially due to the variety of assessment tools and cut-offs. The results may not be generalized to minorities. Studies on the prevalence of clinical diagnoses are needed. Based on our results it is not possible to firmly affirm that the COVID-19 pandemic was the main factor that directly increased perinatal depression and anxiety during the past few years. Future studies should study other factors' impact.

The Association of Vitamin D with Non-Melanoma Skin Cancer Risk: An Umbrella Review of Systematic Reviews and Meta-Analyses

Background and Objectives: Previous studies revealed the anti-angiogenic, antiproliferative, and anti-inflammatory effects of Vitamin D (VitD) on cancer cells. Although this body of evidence supported the correlation of high VitD levels with reduced incidence rates for various malignancies, contradictory results were reported regarding non-melanoma skin cancer (NMSC). The aim of this overview was to summarize the available evidence from the existing pool of systematic reviews and meta-analyses, focusing on VitD serum status, dietary intake, and VitD receptor (VDR) polymorphisms in correlation to NMSC incidence. Materials and Methods: A literature search in electronic databases was conducted from inception to January 2023. The inclusion criteria were systematic reviews and meta-analyses published in peer-reviewed journals, evaluating VitD serum levels, dietary and/or supplementary intake, or VDR gene polymorphisms, and reporting data on NMSC. Results: A total of 10 studies were included in the data analysis models. A positive association between VitD serum levels and NMSC is highlighted. However, dietary/supplementation of VitD does not exhibit a likewise strong linkage to NMSC. Despite the contradictory findings, VDR polymorphisms may play a crucial role in the intricate NMSC pathogenesis. Conclusions: This umbrella review shows that high VitD levels are associated with increased NMSC incidence, potentially due to its direct correlation with increased sun exposure. Further research on VDR polymorphisms is suggested to explore their true effect size on NMSC risk.

Reporting of adverse events of treatment interventions in multiple myeloma: an overview of systematic reviews

The present study is an overview of systematic reviews focusing on adverse events of antimyeloma treatments. It provides a systematic description of adverse events as they are reported in the systematic reviews as well as a critical appraisal of included reviews. We conducted a comprehensive literature search in the most widely used electronic databases looking for systematic reviews that had an adverse event of an antimyeloma treatment intervention as primary outcome. Two independent reviewers conducted selection of included studies and data extraction on predesigned online forms and assessed study quality using AMSTAR 2. Overall corrected covered area (CCA) was calculated to examine the overlap of primary studies across systematic reviews. After screening eligible studies, 23 systematic reviews were included in this overview. Seven reviews with overall CCA of 14.7% examined cardiovascular adverse events of different drugs, including immunomodulatory drugs and proteasome inhibitors (mainly carfilzomib). Nine focused on infections, presenting with overall CCA of 5.8%, each one focused on a different drug or drug class. Three studied thromboembolism in patients treated either with lenalidomide, any immunomodulatory drug, or with daratumumab and had an overall CCA equal to 1.5%. Four more reviews focused on bortezomib-associated neurotoxicity, carfilzomib-associated renal toxicity, or second primary malignancies as an adverse event of lenalidomide or anti-CD38 monoclonal antibody treatment. The quality of included studies as judged by AMSTAR 2 was mostly critically low. Absence of a priori registered protocol and formal assessment of risk of bias of included primary studies were the most common shortcomings. Reporting of antimyeloma drug-associated toxicity is supported by multiple systematic reviews; nevertheless, methodological quality of existing reviews is mostly low.

Higher risk of adverse cardiovascular outcomes in females with type 2 diabetes Mellitus: an Umbrella review of systematic reviews

BACKGROUND

Previous studies have shown that females with type 2 diabetes mellitus (T2DM) may have excess mortality risk compared to their male counterparts. An important next step to address the high global burden of T2DM and cardiovascular disease (CVD) is an umbrella review to summarize data on sex differences in cardiovascular outcomes for patients with T2DM and assess the strength of the evidence observed.

METHODS AND RESULTS

Medline and Embase were searched from inception till 7 August 2022 for systematic reviews and meta-analyses studying the effects of sex on cardiovascular outcomes in T2DM patients. Results from reviews were synthesized with a narrative synthesis, with a tabular presentation of findings and forest plots for reviews that performed a meta-analysis. 27 review articles evaluating sex differences in cardiovascular outcomes were included. Females with T2DM had a higher risk of developing coronary heart disease (CHD; RRR: 1.52, 95%CI: 1.32-1.76, P < 0.001), acute coronary syndrome (ACS; RRR: 1.38, 95%CI: 1.25-1.52, P < 0.001), heart failure (RRR: 1.09, 95%CI: 1.05-1.13, P < 0.001) than males. Females had a higher risk of all-cause mortality (RRR: 1.13, 95%CI: 1.07-1.19, P < 0.001), cardiac mortality (RRR: 1.49, 95%CI: 1.11-2.00, P = 0.009) and CHD mortality (RRR: 1.44, 95%CI: 1.20-1.73, P < 0.001) as compared to males.

CONCLUSIONS

This umbrella review demonstrates that females with T2DM have a higher risk of cardiovascular outcomes than their male counterparts. Future research should address the basis of this heterogeneity and epidemiological factors for better quality of evidence, and identify actionable interventions that will narrow these sex disparities.

Overviews of reviews in the cardiovascular field underreported critical methodological and transparency characteristics: a methodological study based on the Preferred Reporting Items for Overviews of Reviews (PRIOR) statement

OBJECTIVES

This study aimed to evaluate the epidemiology, reporting characteristics, and adherence to the Preferred Reporting Items for Overviews of Reviews (PRIOR) statement of overviews of reviews (overviews) of interventions in the cardiovascular field.

STUDY DESIGN AND SETTING

MEDLINE, Scopus, and the Cochrane Database of Systematic Reviews were searched from January 1, 2000, to October 15, 2020. An updated search was performed in MEDLINE, Epistemonikos, and Google Scholar up to August 25, 2022. Overviews of interventions published in English and primarily considering populations, interventions, and outcomes pertinent to the cardiovascular field were eligible. Study selection, data extraction, and PRIOR adherence assessment were performed by two authors independently.

RESULTS

We analyzed 96 overviews. Almost half (43/96 [45%]) were published between 2020 and 2022 and contained a median of 15 systematic reviews (SRs) (interquartile range, 9-28). The commonest title terminology was "overview of (systematic) reviews" (38/96 [40%]). Methods for handling SR overlap were reported in 24/96 (25%), methods for assessing primary study overlap in 18/96 (19%), handling of discrepant data in 11/96 (11%), and methods for methodological quality or risk of bias assessment of the primary studies within SRs in 23/96 (24%). Authors included data sharing statements in 28/96 (29%), complete funding disclosure in 43/96 (45%), protocol registration in 43/96 (45%), and conflict of interest statement in 82/96 (85%) overviews.

CONCLUSION

Insufficient reporting was identified in methodological characteristics unique in overviews' conduct and most transparency markers. Adoption of PRIOR from the research community could ameliorate overviews' reporting.

Patterns of polysomnography parameters in 27 neuropsychiatric diseases: an umbrella review

BACKGROUND

We provide an umbrella review of the reported polysomnographic changes in patients with neuropsychiatric diseases compared with healthy controls.

METHODS

An electronic literature search was conducted in EMBASE, MEDLINE, All EBM databases, CINAHL, and PsycINFO. Meta-analyses of case-control studies investigating the polysomnographic changes in patients with neuropsychiatric diseases were included. For each meta-analysis, we estimated the summary effect size using random effects models, the 95% confidence interval, and the 95% prediction interval. We also estimated between-study heterogeneity, evidence of excess significance bias, and evidence of small-study effects. The levels of evidence of polysomnographic changes in neuropsychiatric diseases were ranked as follows: not significant, weak, suggestive, highly suggestive, or convincing.

RESULTS

We identified 27 articles, including 465 case-control studies in 27 neuropsychiatric diseases. The levels of evidence of polysomnographic changes in neuropsychiatric diseases were highly suggestive for increased sleep latency and decreased sleep efficiency (SE) in major depressive disorder (MDD), increased N1 percentage, and decreased N2 percentage, SL and REML in narcolepsy, and decreased rapid eye movement (REM) sleep percentage in Parkinson's disease (PD). The suggestive evidence decreased REM latency in MDD, decreased total sleep time and SE in PD, and decreased SE in posttraumatic stress disorder and in narcolepsy.

CONCLUSIONS

The credibility of evidence for sleep characteristics in 27 neuropsychiatric diseases varied across polysomnographic variables and diseases. When considering the patterns of altered PSG variables, no two diseases had the same pattern of alterations, suggesting that specific sleep profiles might be important dimensions for defining distinct neuropsychiatric disorders.

Efficacy and safety of sodium-glucose cotransporter-2 inhibitors in heart failure with mildly reduced or preserved ejection fraction: an overview of 36 systematic reviews

The recently published randomized trials (RCTs) evaluating the effect of Sodium-glucose cotransporter-2 inhibitors (SGLT2i) in heart failure with mildly reduced (HFmrEF) or preserved ejection fraction (HFpEF) led researchers to perform a plethora of systematic reviews (SRs), often providing contradictory conclusions. This overview of reviews was aimed at summarizing the evidence of these SRs, quantifying the overlap, re-analyzing the evidence in case new studies that were identified, and mapping knowledge gaps. Literature search was conducted through Medline, Scopus, and Cochrane until March 22, 2023. Overall, 36 SRs synthesizing results from 18 RCTs were identified. A substantial overlap was identified among the SRs synthesizing large heart failure or cardiovascular outcome trials (CVOTs). Regarding the composite outcome of cardiovascular (CV) mortality or hospitalization for heart failure (HHF), all authors reported a significant favorable effect. A beneficial effect was also noted for CV and all-cause mortality, albeit not significant. Our meta-analysis demonstrated a significant improvement in health-related quality-of-life (HRQoL) as assessed by the Kansas City Cardiomyopathy Questionnaire Overall Summary Score (KCCQ-OSS, MD = 1.97, p < 0.001), Total Symptom Score (KCCQ-TSS, MD = 2.29, p < 0.001), Clinical Summary Score (KCCQ-CSS, MD = 1.59, p < 0.001), and the 6-min walking distance (MD = 10.78 m, p = 0.032). Regarding safety, SGLT2i were associated with a significantly lower risk of serious adverse events compared to placebo (RR = 0.94, p = 0.002). The use of SGLT2i in HFpEF is both efficient and safe. Further research is required to clarify the impact of SGTL2i on different subphenotypes of HFpEF and the cardiorespiratory capacity of these patients.

Gwet's AC1 is not a substitute for Cohen's kappa - A comparison of basic properties

Gwet's AC1 has been proposed as an alternative to Cohen's kappa in evaluating the agreement between two binary ratings. This approach is becoming increasingly popular, and researchers have been criticized for still using Cohen's kappa. However, a rigorous discussion of properties of Gwet's AC1 is still missing. In this paper several basic properties of Gwet's AC1 are investigated and compared with those of Cohen's kappa, in particular the dependence on the prevalence of positive ratings for a given agreement rate and the behaviour in case of no association or maximal disagreement. Both approaches compare the observed agreement rate with a comparative number. Cohen's kappa uses an expected agreement rate as comparator, whereas Gwet's AC1 uses an expected disagreement rate. Consequently, for a fixed agreement rate, Gwet's AC1 increases with increasing difference of the prevalence of positive ratings from 0.5. In contrast, Cohen's kappa decreases. Gwet's AC1 can take positive and negative values in the case of no association between the two raters, whereas Cohen's kappa is 0. Due to these fundamental differences, Gwet's AC1 should not be seen as a substitute for Cohen's kappa. In particular, the verbal classification of kappa values by Landis & Koch should not be applied to Gwet's AC1.

School closures during COVID-19: an overview of systematic reviews

OBJECTIVES

To assess the benefits and drawbacks of school closures and in-school mitigations during the COVID-19 pandemic.

DESIGN

Overview of systematic reviews (SRs).

SEARCH METHODS

We searched six databases and additional resources on 29 July 2022: MEDLINE, Embase, Google Scholar, Cochrane Library, COVID-END inventory of evidence synthesis, and Epistemonikos.

ELIGIBILITY CRITERIA

We selected SRs written in English that answered at least one of four specific questions concerning the efficacy and drawbacks of school closures. Their primary studies were conducted in primary and secondary schools, including pupils aged 5-18. Interventions included school closures or mitigations (such as mask usage) introduced in schools.

DATA COLLECTION AND ANALYSIS

We used AMSTAR 2 to assess confidence in the included SRs, and GRADE was used to assess certainty of evidence. We performed a narrative synthesis of the results, prioritising higher-quality SRs, those which performed GRADE assessments and those with more unique primary studies. We also assessed the overlap between primary studies included in the SRs.

MAIN OUTCOME MEASURES

Our framework for summarising outcome data was guided by the following questions: (1) What is the impact of school closures on COVID-19 transmission, morbidity or mortality in the community? (2) What is the impact of COVID-19 school closures on mental health (eg, anxiety), physical health (eg, obesity, domestic violence, sleep) and learning/achievement of primary and secondary pupils? (3) What is the impact of mitigations in schools on COVID-19 transmission, morbidity or mortality in the community? and (4) What is the impact of COVID-19 mitigations in schools on mental health, physical health and learning/achievement of primary and secondary pupils?

RESULTS

We identified 578 reports, 26 of which were included. One SR was of high confidence, 0 moderate, 10 low and 15 critically low confidence. We identified 132 unique primary studies on the effects of school closures on transmission/morbidity/mortality, 123 on learning, 164 on mental health, 22 on physical health, 16 on sleep, 7 on domestic violence and 69 on effects of in-school mitigations on transmission/morbidity/mortality.Both school closures and in-school mitigations were associated with reduced COVID-19 transmission, morbidity and mortality in the community. School closures were also associated with reduced learning, increased anxiety and increased obesity in pupils. We found no SRs that assessed potential drawbacks of in-school mitigations on pupils. The certainty of evidence according to GRADE was mostly very low.

CONCLUSIONS

School closures during COVID-19 had both positive and negative impacts. We found a large number of SRs and primary studies. However, confidence in the SRs was mostly low to very low, and the certainty of evidence was also mostly very low. We found no SRs assessing the potential drawbacks of in-school mitigations on children, which could be addressed moving forward. This overview provides evidence that could inform policy makers on school closures during future potential waves of COVID-19.

Effectiveness of interventions to prevent perinatal depression: An umbrella review of systematic reviews and meta-analysis

BACKGROUND

To date, dozens of systematic reviews (SRs) and meta-analyses (MAs) summarize the effectiveness of preventive interventions for perinatal depression. However, the results are inconclusive, making an urgent need to step up to higher levels of evidence synthesis.

AIMS

To summarize and compare the evidence from the SR&MA examining the effectiveness of all types of interventions for preventing perinatal depression.

METHOD

PubMed, PsycINFO, Cochrane Database of Systematic Reviews and OpenGrey were searched from inception to December 2022. We selected SR&MA of randomized controlled trials (RCTs) that compared all types of preventive interventions for perinatal depression with control groups whose outcome was the reduction of depressive symptoms and/or incidence of new cases of perinatal depression (PROSPERO: CRD42020173125).

RESULTS

A total of 19 SRs and MAs evaluated 152 unique RCTs that included 83,408 women from 26 countries and five continents. The median effect size for any intervention was SMD = 0.29 (95% CI: 0.20 to 0.38). Exercise/physical activity-based, psychological, and any type of intervention showed median effect sizes of 0.43, 0.28 and 0.36, respectively. The degree of overlap among RCTs was slight. According to AMSTAR-2, 79% of them were rated as low or critically low-quality. The strength of evidence, according to GRADE, was poorly reported and, in most cases, was low.

CONCLUSIONS

Exercise/physical activity-based and psychological interventions have a small-to-medium effect on reducing perinatal depressive symptoms. There is insufficient evidence to conclude that dietary supplements and pharmacological interventions are effective in preventing perinatal depression. There is a need for high-quality SR&MA of RCTs, mainly focusing on universal preventive interventions.

Types and associated methodologies of overviews of reviews in health care: a methodological study with published examples

OBJECTIVES

To provide a descriptive insight into the different types of research questions/objectives and associated methodologies of overviews of reviews, supplemented by representative examples from the health care literature.

STUDY DESIGN AND SETTING

We searched in methodological articles for information on types and methodologies used in overviews and we explored the typology of reviews to identify similar types in literature of overviews. We categorized the types of overviews based on the research question/objective and the methodological approach used. Indicative examples for each category were selected from a sample of 2,121 overviews that were retrieved between 2000 and 2022 from MEDLINE, Scopus, and Cochrane Database of Systematic Reviews.

RESULTS

Based on type of research question, overviews were classified as overviews of reviews of interventions, associations, prediction, diagnostic accuracy, prevalence/incidence, experiences/views, economic evaluation, and measurement properties. Based on the methodological approach, we identified a variety of methods (systematic, living, rapid, scoping, evidence mapping, framework, and methodological) used in overviews.

CONCLUSION

The proposed classification and examples provide an essential starting point for future theory-building research on typologies and study designs of overviews of reviews. It is important for methodologists to make vigorous effort to create consensus-based methodological and reporting guidelines to cover these diverse types and key methodological challenges.

Reporting guideline for overviews of reviews of healthcare interventions: development of the PRIOR statement

OBJECTIVE

To develop a reporting guideline for overviews of reviews of healthcare interventions.

DESIGN

Development of the preferred reporting items for overviews of reviews (PRIOR) statement.

PARTICIPANTS

Core team (seven individuals) led day-to-day operations, and an expert advisory group (three individuals) provided methodological advice. A panel of 100 experts (authors, editors, readers including members of the public or patients) was invited to participate in a modified Delphi exercise. 11 expert panellists (chosen on the basis of expertise, and representing relevant stakeholder groups) were invited to take part in a virtual face-to-face meeting to reach agreement (≥70%) on final checklist items. 21 authors of recently published overviews were invited to pilot test the checklist.

SETTING

International consensus.

INTERVENTION

Four stage process established by the EQUATOR Network for developing reporting guidelines in health research: project launch (establish a core team and expert advisory group, register intent), evidence reviews (systematic review of published overviews to describe reporting quality, scoping review of methodological guidance and author reported challenges related to undertaking overviews of reviews), modified Delphi exercise (two online Delphi surveys to reach agreement (≥70%) on relevant reporting items followed by a virtual face-to-face meeting), and development of the reporting guideline.

RESULTS

From the evidence reviews, we drafted an initial list of 47 potentially relevant reporting items. An international group of 52 experts participated in the first Delphi survey (52% participation rate); agreement was reached for inclusion of 43 (91%) items. 44 experts (85% retention rate) completed the second Delphi survey, which included the four items lacking agreement from the first survey and five new items based on respondent comments. During the second round, agreement was not reached for the inclusion or exclusion of the nine remaining items. 19 individuals (6 core team and 3 expert advisory group members, and 10 expert panellists) attended the virtual face-to-face meeting. Among the nine items discussed, high agreement was reached for the inclusion of three and exclusion of six. Six authors participated in pilot testing, resulting in minor wording changes. The final checklist includes 27 main items (with 19 sub-items) across all stages of an overview of reviews.

CONCLUSIONS

PRIOR fills an important gap in reporting guidance for overviews of reviews of healthcare interventions. The checklist, along with rationale and example for each item, provides guidance for authors that will facilitate complete and transparent reporting. This will allow readers to assess the methods used in overviews of reviews of healthcare interventions and understand the trustworthiness and applicability of their findings.

Diet and Risk of Gastric Cancer: An Umbrella Review

Several dietary exposures have been associated with gastric cancer (GC), but the associations are often heterogenous and may be afflicted by inherent biases. In the context of an Umbrella Review (UR), we provide an overview and a critical evaluation of the strength and quality, and evidence classification of the associations of diet-related exposures in relation to the risk of GC. We searched PubMed and Scopus for eligible meta-analyses of observational studies published in English from inception to 12 December 2021, and for any identified association, we applied robust epidemiological validity evaluation criteria and individual study quality assessment using AMSTAR. We screened 3846 titles/abstracts and assessed 501 full articles for eligibility, of which 49 were included in the analysis, investigating 147 unique exposures in relation to GC, cardia (GCC) or non-cardia (GNCC) cancer. Supported by suggestive evidence, positive associations were found comparing the highest vs. lowest categories for: heavy (>42 g/day) alcohol consumption (Relative Risk (RR) = 1.42, 95% Confidence Interval (CI): 1.20−1.67), salted fish consumption (RR = 1.56, 95% CI:1.30−1.87) and waist circumference (RR = 1.48, 95% CI:1.24−1.78) and an inverse association for the healthy lifestyle index (RR = 0.60, 95% CI:0.48−0.74) in relation to GC. Additionally, a positive association was found comparing obese individuals (Body Mass Index (BMI) ≥ 30) to normal-weight individuals (BMI: 18.5−25) (RR = 1.82, 95% CI:1.32−2.49) in relation to GCC. Most of the meta-analyses were of medium-to-high quality (median items: 7.0, interquartile range: 6−9). Maintaining a normal body weight and adopting healthy dietary choices, in particular, limiting the consumption of salt-preserved foods and alcohol, can reduce the risk of gastric cancer.

Prediabetes and risk of mortality, diabetes-related complications and comorbidities: umbrella review of meta-analyses of prospective studies

AIMS/HYPOTHESIS

The term prediabetes is used for individuals who have impaired glucose metabolism whose glucose or HbA_1c levels are not yet high enough to be diagnosed as diabetes. Prediabetes may already be associated with an increased risk of chronic 'diabetes-related' complications. This umbrella review aimed to provide a systematic overview of the available evidence from meta-analyses of prospective observational studies on the associations between prediabetes and incident diabetes-related complications in adults and to evaluate their strength and certainty.

METHODS

For this umbrella review, systematic reviews with meta-analyses reporting summary risk estimates for the associations between prediabetes (based on fasting or 2 h postload glucose or on HbA_1c) and incidence of diabetes-related complications, comorbidities and mortality risk were included. PubMed, Web of Science, the Cochrane Library and Epistemonikos were searched up to 17 June 2021. Summary risk estimates were recalculated using a random effects model. The certainty of evidence was evaluated by applying the GRADE tool. This study is registered with PROSPERO, CRD42020153227.

RESULTS

Ninety-five meta-analyses from 16 publications were identified. In the general population, prediabetes was associated with a 6-101% increased risk for all-cause mortality and the incidence of cardiovascular outcomes, CHD, stroke, heart failure, atrial fibrillation and chronic kidney disease, as well as total cancer, total liver cancer, hepatocellular carcinoma, breast cancer and all-cause dementia with moderate certainty of evidence. No associations between prediabetes and incident depressive symptoms and cognitive impairment were observed (with low or very low certainty of evidence). The association with all-cause mortality was stronger for prediabetes defined by impaired glucose tolerance than for prediabetes defined by HbA_1c.

CONCLUSIONS/INTERPRETATION

Prediabetes was positively associated with risk of all-cause mortality and the incidence of cardiovascular outcomes, CHD, stroke, chronic kidney disease, cancer and dementia. Further high-quality studies, particularly on HbA_1c-defined prediabetes and other relevant health outcomes (e. g. neuropathy) are required to support the evidence.

Introduction to PRISMA 2020 and implications for research synthesis methodologists

Systematic reviews should be reported completely and accurately so that users can interpret and appraise the review findings appropriately. In this commentary, we describe key features of a major update of the Preferred Reporting Items for Systematic reviews and Meta-Analyses statement-PRISMA 2020-and discuss its implications for research synthesis methodologists.

The Effect of Phosphodiesterase-type 5 Inhibitors on Erectile Function: An Overview of Systematic Reviews

Background: Multiple systematic reviews explore the effect of phosphodiesterase type 5 (PDE5) inhibitors on erectile dysfunction (ED), with each study addressing specific outcomes. However, physicians and policymakers require a holistic approach of this topic.

Objective: To summarize the current evidence regarding the efficacy and safety of PDE5 inhibitors for the management of ED through an overview of systematic reviews.

Methods: Studies were identified by searching PubMed, Web of Science, Cochrane Library and Scopus databases, as well as sources of grey literature until June 12, 2021 (PROSPERO: CRD42020216754). We considered systematic reviews, meta-analyses or network meta-analyses of randomized trials that provided outcomes about the efficacy and safety of any approved PDE5 inhibitor (avanafil, sildenafil, tadalafil and vardenafil). We constructed forest plots for meta-analytic effects regarding the change in erectile function, adverse events and dropouts after administration of PDE5 inhibitors in the general population and in specific patient groups.

Results: We included 23 studies with 154,796 participants and a total of 258 meta-analytic effects. Sildenafil 25 mg [Weighted Mean Difference (WMD): 13.08, 95% Confidence Interval (CI): 10.1-16.06] seemed to be statistically superior to all interventions in improving erectile function compared to placebo, but studies with low-dose sildenafil are lacking. Moreover, comparing among different PDE5 inhibitors, sildenafil 50 mg or sildenafil 100 mg were considered the most effective compounds in the general population. The latter derived, however, predominantly from indirect comparisons among different PDE5 inhibitors. Still, sildenafil 100 mg was associated with more treatment-related adverse events and dropouts. Interestingly, low-dose daily tadalafil may be more effective than high-dose on-demand tadalafil (WMD: 1.24, 95% CI: 0.03-2.44). Furthermore, testosterone and PDE5 inhibitors in patients with ED and hypogonadism seem to further improve symptoms, while the addition of a-blockers in patients with urinary symptoms treated with PDE5 inhibitors does not provide additional benefits (WMD: −0.8, 95% CI: −1.65-0.06).

Conclusion: Although the efficacy and safety of PDE5 inhibitors, compared to placebo, is well-documented, the existing evidence comparing different PDE5 inhibitors is low. Therefore, high-quality, head-to-head, trials comparing different PDE5 inhibitors are necessary to determine their ideal dosage and formulation based on their safety and efficacy profile.

Systematic Review Registration: PROSPERO, identifier [CRD42020216754].

Effect of phosphodiesterase-type 5 inhibitors on erectile function: an overview of systematic reviews and meta-analyses

INTRODUCTION

Phosphodiesterase-type 5 inhibitors (PDE5i) are the recommended first-line treatment for erectile dysfunction. Previous systematic reviews and meta-analyses suggest that they are a safe and effective option in many patient groups. Similarly, PDE5i may be effective as part of combination therapy in non-responders to PDE5i. We will generate an overview of systematic reviews, meta-analyses and network meta-analyses aiming to summarise the available knowledge regarding the efficacy and safety of PDE5i in the general population and in multiple subgroups of patients.

METHODS AND ANALYSIS

This overview was designed in accordance with the PRIO-harms and Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols guidelines and its protocol was registered at PROSPERO. We will systematically search PubMed, Web of Science, Cochrane Library and Scopus databases from inception to November 2020 without any language restrictions. We will include systematic reviews or meta-analyses: (1) comparing the efficacy and safety of any dose of PDE5i with each other, with placebo or with other effective treatments for the management of erectile function; (2) exploring the use of any PDE5i alone or in combination with other treatment modalities in the general male population or in specific subgroups and (3) conducted with systematic procedures. Our overview will employ the AMSTAR 2 tool to evaluate the quality of the included studies and the Grading of Recommendations Assessment, Development and Evaluation approach to assess the strength of evidence for all outcomes. We will construct forest plots of risk estimates with the corresponding CI for all outcomes.

ETHICS AND DISSEMINATION

In this overview, we will undertake an extensive literature search in an attempt to evaluate the potential benefits and risks of treatment with one PDE5i versus another or versus placebo and provide recommendations for clinicians and policy-makers. No ethical approval is required.

PROSPERO REGISTRATION NUMBER

CRD42020216754.

Global mapping of overviews of systematic reviews in healthcare published between 2000 and 2020: a bibliometric analysis

OBJECTIVE

To conduct a bibliometric analysis using a large sample of overviews of systematic reviews (OoSRs) and reveal research trends and areas of interest about these studies.

STUDY DESIGN AND SETTING

We searched MEDLINE, Scopus and Cochrane Database of Systematic Reviews from 1/1/2000 to 15/10/2020. We used Scopus meta-data and two authors recorded supplementary information independently. We summarized the data using frequencies with percentages.

RESULTS

A total of 1558 studies were considered eligible for analysis. We found that the publications have been increasing yearly and their nomenclature was not uniform (the most frequent label in the title was "overview of systematic reviews"). The largest number of papers and the most cited ones were published by corresponding authors from the UK. The publications were distributed across 737 scholarly journals and many of them were published in the field of complementary/alternative medicine, psychiatry/psychology, nutrition/dietetics, and pediatrics. The co-authorship analysis revealed collaborations among countries. The most common clinical conditions were depression, diabetes, cancer, dementia, pain, cardiovascular disease, stroke, obesity, and schizophrenia.

CONCLUSION

OoSRs have recently become a popular approach of evidence synthesis. International collaborations between overview authors from countries with increased research productivity and countries with less research activity should be encouraged.

Preferred reporting items for journal and conference abstracts of systematic reviews and meta-analyses of diagnostic test accuracy studies (PRISMA-DTA for Abstracts): checklist, explanation, and elaboration

For many users of the biomedical literature, abstracts may be the only source of information about a study. Hence, abstracts should allow readers to evaluate the objectives, key design features, and main results of the study. Several evaluations have shown deficiencies in the reporting of journal and conference abstracts across study designs and research fields, including systematic reviews of diagnostic test accuracy studies. Incomplete reporting compromises the value of research to key stakeholders. The authors of this article have developed a 12 item checklist of preferred reporting items for journal and conference abstracts of systematic reviews and meta-analyses of diagnostic test accuracy studies (PRISMA-DTA for Abstracts). This article presents the checklist, examples of complete reporting, and explanations for each item of PRISMA-DTA for Abstracts.

Joint Protection Programmes for People with Osteoarthritis and Rheumatoid Arthritis of the Hand: An Overview of Systematic Reviews

Purpose: Joint protection has been introduced as a self-management strategy for people with rheumatoid arthritis (RA) and osteoarthritis (OA) of the hand. The purpose of this study was to conduct an overview of systematic reviews (SRs) and critically appraise the evidence to establish the current effectiveness of joint protection for people with hand RA and OA. Method: A comprehensive search was conducted of six databases from January 2008 to May 2018. SRs that evaluated the effectiveness of joint protection for people with hand arthritis were eligible for inclusion. The A MeaSurement Tool to Assess systematic Reviews (AMSTAR) 2 checklist was used to assess the methodological quality of each SR. Results: Nine SRs were included: two were rated as high quality, and seven were rated as low quality. Seven of the nine did not take into account risk of bias when interpreting or discussing their findings, six did not assess publication bias, and five did not register their protocol. The high-quality reviews found no clinically important benefit of joint protection for pain, hand function, and grip strength levels. The low-quality reviews reported improvements in function, pain, grip strength, fatigue, depression, self-efficacy, joint protection behaviours, and disease symptoms in people with RA. Conclusions: High-quality evidence from high-quality reviews found a lack of any clinically important benefit of joint protection programmes for pain, hand function, and grip strength outcomes, whereas low-quality evidence from low-quality reviews found improvements in these outcomes.

Qualitative research methods in medical dissertations: an observational methodological study on prevalence and reporting quality of dissertation abstracts in a German university

Background

Qualitative methods offer a unique contribution to health research. Academic dissertations in the medical field provide an opportunity to explore research practice. Our aim was to assess the use of qualitative methods in dissertations in the medical field.

Methods

By means of a methodological observational study, an analysis of all academic medical dissertations’ abstracts between 1998 and 2018 in a repository databank of a large medical university faculty in Germany was performed. This included MD dissertations (Dr. med. (dent.)) and medical science dissertations (Dr. sc. hum.). All abstracts including “qualitativ*” were screened for studies using qualitative research methods. Data were extracted from abstracts using a category grid considering a) general characteristics (year, language, degree type), b) discipline, c) study design (mixed methods/qualitative only, data conduction, data analysis), d) sample (size and participants) and e) technologies used (data analysis software and recording technology). Thereby reporting quality was assessed.

Results

In total, 103 abstracts of medical dissertations between 1998 and 2018 (1.4% of N = 7619) were included, 60 of MD dissertations and 43 of medical sciences dissertations. Half of the abstracts (n = 51) referred to dissertations submitted since 2014. Most abstracts related to public health/hygiene (n = 27) and general practice (n = 26), followed by medical psychology (n = 19). About half of the studies (n = 47) used qualitative research methods exclusively, the other half (n = 56) used mixed methods. For data collection, primarily individual interviews were used (n = 80), followed by group interviews (n = 33) and direct observation (n = 11). Patients (n = 36), physicians (n = 36) and healthcare professionals (n = 17) were the most frequent research participants. Incomplete reporting of participants and data analysis was common (n = 67). Nearly half of the abstracts (n = 46) lacked information on how data was analysed, most of the remaining (n = 43) used some form of content analysis. In summary, 36 abstracts provided all crucial data (participants, sample size,; data collection and analysis method).

Conclusion

A small number of academic dissertations used qualitative research methods. About a third of these reported all key aspects of the methods used in the abstracts. Further research on the quality of choice and reporting of methods for qualitative research in dissertations is recommended.

Methods for depicting overlap in overviews of systematic reviews: An introduction to static tabular and graphical displays

BACKGROUND AND OBJECTIVE

To introduce potential static tabular and graphical techniques for visually presenting overlap between systematic reviews (SRs) included in overviews of systematic reviews (OoSRs).

METHODS

The graphical approaches described include Venn and Euler diagrams, as well as matrix-based, node-link, and aggregation-based techniques. We used fundamental concepts of mathematics from set and network theory to develop our novel graphical approaches. The graphical displays were created using R.

RESULTS

Overview authors have the flexibility to choose from a variety of visualizations, depending on the characteristics of their study. If the OoSRs include few SRs, a Venn or an Euler diagram can be used. In case of OoSRs with more SRs, Upset plots, heatmaps, and node-link graphs are more appropriate for visualizing overlapping SRs. Stacked bar plots constitute an aggregation-based technique of illustrating overlap. Strengths and limitations of each graphical approach are presented.

CONCLUSION

The degree of overlap should be explored for the entire study and for specific outcomes of interest. The proposed graphical techniques may assist methodologists and authors in identifying overlap, which in turn may improve validity and transparency in OoSRs. More research is needed to understand which technique would be most useful and easiest to understand.

Exploring the effectiveness of technology-based learning on the educational outcomes of undergraduate healthcare students: an overview of systematic reviews protocol

INTRODUCTION

Rapid technology development due to the introduction of Industrial Revolution 4.0 and Internet of Things has created a demand and gradual transition from traditional teaching and learning to technology-based learning in higher education, including healthcare education. The COVID-19 pandemic has accelerated this process, with educators now required to quickly adapt to and adopt such changes. The abundance of available systematic reviews has made the effectiveness of such approaches ambiguous especially in healthcare education. Therefore, a protocol of the overview of systematic reviews (OoSR) is planned to extrapolate the effectiveness of technology-based learning in undergraduate healthcare education.

METHODS AND ANALYSIS

Scopus, CINAHL, Academic Search Complete, Cochrane Library, MEDLINE and Psychology and Behavioral Sciences Collection databases were selected. Screening was conducted independently by at least two authors and the decision for inclusion was done through discussion or involvement of an arbiter against a predetermined criteria. Included articles will be evaluated for quality using A MeaSurement Tool to Assess systematic Reviews and Risk of Bias in Systematic Review tools, while primary systematic review articles will be cross-checked and reported for any overlapping using the 'corrected covered area' method. Only narrative synthesis will be employed according to the predefined themes into two major dimensions-theory and knowledge generation (focusing on cognitive taxonomy due to its ability to be generalised across disciplines), and clinical-based competence (focusing on psychomotor and affective taxonomies due to discipline-specific influence). The type of technology used will be identified and extracted.

ETHICS AND DISSEMINATION

The OoSR involves analysis of secondary data from published literature, thus ethical approval is not required. The findings will provide a valuable insight for policymakers, stakeholders, and researchers in terms of technology-based learning implementation and gaps identification. The findings will be published in several reports due to the extensiveness of the topic and will be disseminated through peer-reviewed publications and conferences.

PROSPERO REGISTRATION NUMBER

CRD4202017974.

Effects of glutamine supplementation on critically ill patients: Focus on efficacy and safety. An overview of systematic reviews

OBJECTIVES

The aim of this overview of systematic reviews was to synthesize, appraise, and present all systematic review (SR) evidence on the clinical efficacy of glutamine administration to severely ill patients.

METHODS

Medline, Scopus, the Cochrane Library, and Prospero were searched up to March 2020. Systematic reviews and meta-analyses of randomized controlled trials published in English, comparing immunomodulating diets-containing exclusively glutamine-with standard diets for critically ill adult patients were selected. Data were collected from each selected systematic review and all available primary studies. The primary outcome was overall mortality; secondary outcomes were rate of infectious complications, hospital and intensive care unit (ICU) length of stay (LOS).

RESULTS

Seventeen SRs were eligible for inclusion. Of the SRs, 16 included meta-analyses with moderate degree of overlap (corrected covered area = 10%). These included 117 randomized controlled trials with 9933 patients. Glutamine supplementation was not associated with overall mortality and ICU LOS. However, it may reduce the rate of infectious complications overall (N = 3666, risk ratio, 0.82; 95% confidence interval [CI], 0.73-0.92; I² = 33%: low quality of evidence). LOS was limited with the supplementation of glutamine (N = 4353 weighted mean difference, -2.90; 95% CI, -3.66 to -2.15; I² = 81%: very low quality of evidence), but this effect was diminished when only studies with low risk for bias were synthesized.

CONCLUSION

Glutamine could demonstrate a beneficial role in critical care patients of diminishing the rate of infectious complications and hospital and ICU LOS. However, future studies with better quality would confirm this finding.

Association of glucose-lowering medications with cardiovascular outcomes: an umbrella review and evidence map

BACKGROUND

Considering the global burden of diabetes and associated cardiovascular disease, an urgent need exists for the best treatment, which should be based on the best available evidence. We examined the association between glucose-lowering medications and a broad range of cardiovascular outcomes, and assessed the strength of evidence for these associations.

METHODS

For this umbrella review we searched PubMed, Embase, and the Cochrane Library to identify systematic reviews and meta-analyses of randomised controlled trials examining the cardiovascular safety of glucose-lowering medications. Cardiovascular outcomes examined included major adverse cardiovascular events, cardiovascular death, myocardial infarction, stroke, heart failure, unstable angina, and atrial fibrillation. For each meta-analysis, we estimated the relative risk (RR) and 95% CI. We also created an evidence map showing the plausible benefits or harms of each intervention and the certainty of the evidence.

FINDINGS

We examined 232 meta-analyses evaluating ten classes of diabetes drugs. We identified six risk and 38 protective associations showing a high strength of evidence. Six associations increased the risk of cardiovascular disease, including glimepiride (stroke [RR 2·01; 95% CI 1·02-3·98]), rosiglitazone (myocardial infarction [1·28; 1·02-1·62] and heart failure [1·72, 1·31-2·27]), and pioglitazone (heart failure [1·40; 1·16-1·69]). 38 associations decreased the risk of cardiovascular disease, including glucagon-like peptide-1 receptor agonists as a class (major adverse cardiovascular events [RR 0·88; 95% CI 0·84-0·92], death from cardiovascular disease [0·87; 0·81-0·94], myocardial infarction [0·92; 0·86-0·99], stroke [0·84; 0·77-0·93], and heart failure [0·90; 0·83-0·99]), albiglutide (major adverse cardiovascular events [0·81; 0·68-0·96], myocardial infarction [0·77; 0·64-0·92], and heart failure [0·71; 0·55-0·93]), dulaglutide (stroke [0·78; 0·64-0·96]), exenatide (major adverse cardiovascular events [0·91; 0·83-1·00]), liraglutide (major adverse cardiovascular events [0·86; 0·77-0·96]), semaglutide (major adverse cardiovascular events [0·76; 0·62-0·92] and stroke [0·67; 0·45-1·00]), sodium-glucose co-transporter-2 inhibitors as a class (major adverse cardiovascular events [0·87; 0·82-0·93], death from cardiovascular disease [0·82; 0·75-0·90], myocardial infarction [0·86; 0·78-0·94], and heart failure [0·68; 0·63-0·73]), canagliflozin (major adverse cardiovascular events [0·84; 0·75-0·93], death from cardiovascular disease [0·82; 0·71-0·96], and heart failure [0·65; 0·54-0·78]), dapagliflozin (heart failure [0·70; 0·60-0·82]), empagliflozin (major adverse cardiovascular events [0·85; 0·77-0·94], death from cardiovascular disease [0·62; 0·50-0·78], and heart failure [0·64; 0·53-0·77]), and pioglitazone (major adverse cardiovascular events [0·84; 0·74-0·96], myocardial infarction [0·80; 0·67-0·95], and stroke [0·79; 0·65-0·95]).

INTERPRETATION

We found varied levels of evidence for the associations between diabetes drugs and cardiovascular outcomes; some drugs raised the risk of cardiovascular disease, whereas others showed benefit.

FUNDING

None.

The Principles of Biomedical Scientific Writing: Abstract and Keywords

An abstract is a self-contained, short, powerful statement that describes a larger body of work. It may be incorporated as part of a published paper, book, grant proposal, thesis, research report, or a conference paper. An abstract of a scientific paper will be published online independently, so it should make sense when it is read alone. An abstract of a hypothesis-testing paper consists of at least four key elements, as follows: (1) study question/hypothesis/aim, (2) experiments/material and methods, (3) results, and (4) response to the question/conclusion(s). The abstract usually begins with a background and may end in applications, recommendations, implications, or speculations. The abstract is one of the many features of a manuscript that competes for the readers' attention; therefore, it should be informative, accurate, attractive, and concise. Since a huge amount of work must be compressed into a few sentences, writing an abstract may be a difficult task that needs professional skills. Here, we provide a practical guide to writing an abstract and selecting keywords for a hypothesis-testing medical paper.

Preferred Reporting Items for Overviews of Reviews (PRIOR): a protocol for development of a reporting guideline for overviews of reviews of healthcare interventions

BACKGROUND

Overviews of reviews (i.e., overviews) compile information from multiple systematic reviews to provide a single synthesis of relevant evidence for healthcare decision-making. Despite their increasing popularity, there are currently no systematically developed reporting guidelines for overviews. This is problematic because the reporting of published overviews varies considerably and is often substandard. Our objective is to use explicit, systematic, and transparent methods to develop an evidence-based and agreement-based reporting guideline for overviews of reviews of healthcare interventions (PRIOR, Preferred Reporting Items for Overviews of Reviews).

METHODS

We will develop the PRIOR reporting guideline in four stages, using established methods for developing reporting guidelines in health research. First, we will establish an international and multidisciplinary expert advisory board that will oversee the conduct of the project and provide methodological support. Second, we will use the results of comprehensive literature reviews to develop a list of prospective checklist items for the reporting guideline. Third, we will use a modified Delphi exercise to achieve a high level of expert agreement on the list of items to be included in the PRIOR reporting guideline. We will identify and recruit a group of up to 100 international experts who will provide input into the guideline in three Delphi rounds: the first two rounds will occur via online survey, and the third round will occur during a smaller (8 to 10 participants) in-person meeting that will use a nominal group technique. Fourth, we will produce and publish the PRIOR reporting guideline.

DISCUSSION

A systematically developed reporting guideline for overviews could help to improve the accuracy, completeness, and transparency of overviews. This, in turn, could help maximize the value and impact of overviews by allowing more efficient interpretation and use of their research findings.

Assessment of the abstract reporting of systematic reviews of dose-response meta-analysis: a literature survey

Background

There is an increasing number of published systematic reviews (SR) of dose-response meta-analyses (DRMAs) over the past decades. However, the quality of abstract reporting of these SR-DRMAs remains to be understood. We conducted a literature survey to investigate the abstract reporting of SR-DRMAs.

Methods

Medline, Embase, and Wiley online Library were searched for eligible SR-DRMAs. The reporting quality of SR-DRMAs was assessed by the modified PRISMA-for-Abstract checklist (14 items). We summarized the adherence rate of each item and categorized them as well complied (adhered by 80% or above), moderately complied (50 to 79%), and poorly complied (less than 50%). We used total score to reflect the abstract quality and regression analysis was employed to explore the potential influence factors for it.

Results

We included 529 SR-DRMAs. Eight of 14 items were moderately (3 items) or poorly complied (5 items) while only 6 were well complied by these SR-DRMAs. Most of the SR-DRMAs failed to describe the methods for risk of bias assessment (30.2, 95% CI: 26.4, 34.4%) and the results of bias assessment (48.8, 95% CI: 44.4, 53.1%). Few SR-DRMAs reported the funding (2.3, 95% CI: 1.2, 3.9%) and registration (0.6, 95% CI: 0.1, 1.6%) information in the abstract. Multivariable regression analysis suggested word number of abstracts [> 250 vs. ≤ 250 (estimated ß = 0.31; 95% CI: 0.02, 0.61; P = 0.039)] was positively associated with the abstract reporting quality.

Conclusion

The abstract reporting of SR-DRMAs is suboptimal, substantial effort is needed to improve the reporting. More word number may benefit for the abstract reporting. Given that reporting of abstract largely depends on the reporting and conduct of the SR-DRMA, review authors should also focus on the completeness of SR-DRMA itself.

Electronic supplementary material

The online version of this article (10.1186/s12874-019-0798-5) contains supplementary material, which is available to authorized users.

Gene promoter methylation and cancer: An umbrella review

Gene promoter methylation is a common epigenetic event, taking place in the early phase of tumorigenesis, which has a great potential as a diagnostic and prognostic cancer biomarker. In this umbrella review, we provide an overview on the association between gene-promoter methylation of protein-coding genes and cancer risk based on currently available meta-analyses data on gene promoter methylation. We searched MEDLINE via PubMed and the Cochrane Database of Systematic Reviews for meta-analyses that examine the association between gene-promoter methylation and cancer, published until January 2019 in English. We used AMSTAR to assess the quality of the included studies and applied a set of pre-specified criteria to evaluate the magnitude of each association. We provide a comprehensive overview of 80 unique combinations between 22 different genes and 18 cancer outcomes, all of which indicated a positive association between promoter hypermethylation and cancer. In total, the 70 meta-analyses produced significant results under a random-effects model with odds ratios that ranged from 1.94 to 26.60, with the summary effect being in favor of the unmethylated group in all cases. Three of the strong evidence associations involve RASSF1 methylation on bladder cancer risk (OR = 18.46; 95% CI: 12.69-26.85; I² = 0%), MGMT methylation on NSCLC (OR = 4.25; 95% CI: 2.83-6.38; I² = 22.4%) and RARB methylation on prostate cancer (OR = 6.87; 95% CI: 4.68-10.08; I² = 0%). Meta-analyses showed a moderate quality, AMSTAR score ranging from 4 to 9 (Mdn = 8; IQR: 7.0 to 8.0). As primary studies and meta-analyses on the subject accumulate, more genetic loci may be found to be highly associated with specific cancer types and hence the biomarker sets will become wider.