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Using meta-analysis in psychiatric research.

Meta-analysis is a technique for summarizing the results of many studies which can allow reviewers in a particular field to arrive at a synthesis of the various findings in a more objective manner than relying on expert opinion and combine the results of these studies to arrive at an overall estimate of the magnitude of the effect of a treatment, to determine if the evidence favours its effectiveness. The technique consists of determining an effect size or odds ratio for each study and combining them, taking into account the fact that studies with large samples should exert more influence than those with small samples. However, the procedure is not mechanical. The reviewer must make a series of decisions regarding the studies to be included or excluded, the weight to place on the methodological rigour of the trials, the results from each study to be used, how to handle differences in the magnitude of the results across studies, how to derive the best overall estimate of the effect across studies, and how to determine the precision of that estimate. Each of these decisions can affect both the quality of the review and the nature of the findings.

Humans

Studies of educational interventions and outcomes in diabetic adults: a meta-analysis revisited.

This paper reports a follow-up of previous meta-analysis research conducted by the author on the effects of diabetes patient education on patient outcomes. An expanded sample of studies and psychological outcome variables were added to the previously studied variables of patient knowledge, self-care behaviors (compliance and skill performance) and metabolic control. The purpose was to determine: (1) the effects of patient education on specific outcome variables; and (2) the relationships between effects of education and characteristics of the studies and/or subjects. Following an extensive literature search, a total of 82 studies were found which met the inclusion criteria for this analysis; 68% were published and 32% were unpublished. Homogeneity analyses of specific patient outcome variables yielded the following results: knowledge effects ranged from 0.49 to 1.05; self-care behavior effects from 0.17 to 0.57, with insulin injection and weight loss associated with the smallest effect sizes; metabolic control from 0.16 to 0.41; and psychological outcomes 0.27. Mean age of the subjects was negatively correlated with knowledge and cholesterol, indicating that the older the mean age of the subjects, the lower the effects of patient education on these variables. Findings of this meta-analysis on the expanded data set were consistent with the previous meta-analysis and lend support to the effectiveness of diabetes patient education in improving patient outcomes.

Diabetes Mellitus

5-Fluorouracil (5FU) with or without folinic acid (LV) in human colorectal cancer? Multivariate meta-analysis of the literature.

This meta-analysis is based on 106 evaluations of response from 77 clinical studies about 5-fluorouracil (5FU) treatment with or without leucovorin (LV) in metastatic colorectal carcinoma. Overall, in naive patients, LV is associated with a median response rate of 31% as compared with a 12% figure with 5FU alone. Using a forward stepwise multilinear regression analysis, it is shown that as much as 44% of the variance in the reported response rates in naive patients can be accounted for by treatment-related variables (P less than 0.001). The significant parameters are LV adjunction (partial R = 0.636), cumulative total 5FU dose (R = 0.344), and 5FU weekly schedule (R = 0.246). In pretreated patients, the latter parameter is the only significant one (R = 0.443). Unexpectedly, LV administration behaves like an all-or-nothing governor, without any obvious dose-effect relationship. Protracted 5FU infusion over weeks allows a mean cumulative drug delivery, 3 times higher than bolus regimens (21.3 vs 7.02 g m-2, P less than 0.001) and may represent the best clinical approach to influence the 5FU-related variables. Accordingly, it is suggested that 5FU protracted infusion, titrated to the highest tolerable doses and potentiated with low doses of leucovorin, could represent the most efficacious way for using 5FU in colorectal disseminated cancer. This hypothesis and its eventual impact on survival should be tested in randomized trials.

Colorectal Neoplasms

Complication rates of 16- and 18-gauge needles for native kidney biopsies: a systematic review and proportional meta-analysis.

This systematic review and meta-analysis evaluated complication rates and diagnostic yield reported in studies of adult native kidney biopsy using 16-gauge (16 G) or 18-gauge (18 G) needles. We included randomized trials and cohort studies of real-time ultrasound-guided biopsies, including case series. MEDLINE, Embase, and CENTRAL were searched through October 2024. Two reviewers independently performed study selection, data extraction, and risk of bias assessment using Joanna Briggs Institute tools. Random-effects meta-analyses estimated pooled proportions with 95% confidence intervals (CI), and univariable random-effects meta-regression explored study-level associations with major complications, transfusion, or gross hematuria. We screened 4,499 titles and abstracts and reviewed 319 full-text articles; 62 studies comprising 68 biopsy series were included. The pooled major complication rate in studies using 16 G needles was 1.83% (95% CI: 1.20-2.79) and 1.29% (95% CI: 0.78-2.13) in studies using 18 G needles, with no statistically significant difference. Mean glomerular yield was 18.8 with 16 G and 17.5 with 18 G needles. In study-level meta-regression, studies with higher prevalence of acute kidney injury, lower mean estimated glomerular filtration rate, or lower mean hemoglobin reported higher pooled complication rates. Most studies were single-arm cohorts; between-needle differences therefore reflect indirect study-level contrasts. Interpretation is limited by retrospective design and heterogeneity across studies. Overall, studies using both needle sizes reported low complication rates and similar diagnostic yield, although definitions and reporting varied. Direct comparative studies are needed to determine whether meaningful differences exist.

Humans

Surgery for lumbar spinal stenosis. Attempted meta-analysis of the literature.

A meta-analysis was undertaken to determine the effects of surgery for lumbar spinal stenosis on pain and disability. Seventy-four journal articles met inclusion criteria and were independently reviewed by two readers. On average, 64% of patients treated surgically for lumbar spinal stenosis were reported to have good-to-excellent outcomes. However, there was wide variation across studies in the percentage with good outcomes. Few patient characteristics were found to predict outcome. Major deficits in study design, analysis, and reporting were common, and these precluded firm conclusions.

Adult

Intraocular Pressure Changes Following Intraluminal Stent Removal From the Paul Glaucoma Implant: A Systematic Review and Meta-Analysis.

PURPOSE: This study aims to systematically review and perform a single-arm meta-analysis to comprehensively evaluate the effect of removal of intraluminal stent from the Paul glaucoma implant (PGI) on intraocular pressure (IOP) changes and to summarize its long-term efficacy and safety. CLINICAL RELEVANCE: Glaucoma remains one of the leading global causes of irreversible vision loss, necessitating effective surgical management for refractory cases. Glaucoma drainage devices are critical for these complex forms, and intraluminal stent removal from the PGI serves as a key strategy to titrate aqueous outflow and optimize long-term IOP control. METHODS: A systematic review was conducted by searching EMBASE, Medline, and CENTRAL. The meta-analysis ultimately included 5 observational studies. The Risk of Bias in Nonrandomized Studies of Interventions (ROBINS-I) tool was used to assess the quality of the included studies. Continuous outcomes (eg, postremoval stent IOP reduction) were analyzed using the mean difference (MD) with 95% confidence intervals (CI); dichotomous outcomes (eg, hypotony incidence) were evaluated using pooled proportion with 95% CI. All meta-analyses employed a random-effects model. RESULTS: Our meta-analysis included 5 studies, involving a total of 283 eyes. The meta-analysis revealed that removal of the stent leads to a significant and immediate IOP reduction. The IOP reduction (immediate postremoval stent IOP minus preremoval stent IOP) was significant, with a pooled MD of -9.09 mm Hg IOP (MD = 9.09; 95% CI = [-11.77, -6.41]). In the preremoval stent high-IOP (>21 mm Hg) subgroup, the IOP reduction is -11.82 (95% CI = [-10.14, -13.51]). This reduction was significantly greater than the preremoval stent low-IOP (<21 mm Hg) subgroup, whose reduction is -6.66 mm Hg (95% CI = [-5.55, -7.77]). Regarding safety, the pooled proportion of clinically hypotony was low and highly consistent (I&#xb2; = 0.00%) at only 0.03 (95% CI = [0.00, 0.15]). CONCLUSIONS: Intraluminal stent removal from the PGI is an effective and safe IOP-lowering intervention. Its IOP reduction effect is significantly more pronounced in patients with preremoval stent high IOP, providing crucial clinical guidance for managing persistently high IOP after PGI implantation.

Humans

Meta-analysis of observational epidemiological studies: a review.

Meta-analyses (integration of findings by quantitative analyses of results of individual studies) are already widely used in the psychological and educational sciences and in the pooling of clinical trial results. Examples of the application of such techniques to the results of observational epidemiological studies are now proliferating. In this paper meta-analysis of the results of observational epidemiological studies is reviewed. Uncritical adoption of techniques used in pooled analyses of clinical trial results may be inappropriate. Some alternative approaches, including meta-regression techniques, are discussed, and illustrated with reference to examples of meta-analyses of studies of breast cancer risk following oral contraceptive use and of patterns of post-bereavement mortality. Although substantial difficulties beset the use of meta-analysis in epidemiology, many of these problems are also implicit in the execution of traditional, narrative reviews. Foremost among these difficulties are those associated with publication bias and with making due allowance for the quality of the studies being combined. Unlike traditional narrative reviews, meta-analyses require explicit statement of the criteria for the review and hence highlight these difficulties. Nonetheless, careful and critical application of appropriate meta-analytical techniques facilitates quantitative exploration of inhomogeneities in, and (where appropriate) synthesis of study results.

Epidemiologic Methods

Photon-counting detector computed tomography (PCD-CT) in multiple myeloma: a systematic review and trial sequential meta-analysis on image quality and radiation dose.

OBJECTIVES: To systematically review and perform a meta-analysis comparing the effects of PCD-CT versus EID-CT on image quality (sharpness) and radiation dose (CTDIvol) in patients with bone lesions due to multiple myeloma&#xa0;(MM). METHODS: A comprehensive search of PubMed, Embase, Scopus, and Cochrane Central was conducted from inception to October 2025. Studies comparing PCD-CT and EID-CT in MM patients were included. Methodological quality was assessed using ROBINS-I, and the certainty of evidence was assessed using GRADE. RESULTS: A total of 41 studies were identified that matched our search criteria. After duplicate removal and screening, five studies (n = 170 patients) were included in the systematic review, with four contributing to the meta-analysis. PCD-CT showed a significant pooled mean difference in image sharpness (mean difference, + 0.99 points; 95% CI, 0.62-1.37; p < 0.001). PCD-CT also demonstrated a reduction in radiation dose (mean difference, -4.95 milligrays; 95% CI, -8.39 to -1.50; p = 0.005). Trial sequential analysis (TSA) confirmed stability of pooled estimates, with conclusive evidence for image sharpness improvement, and suggestive yet incomplete evidence for radiation dose reduction. CONCLUSION: Compared to EID-CT in MM, PCD-CT significantly improves subjective image sharpness as supported by trial sequential analysis. Conventional meta-analysis suggested a reduction in radiation dose with PCD-CT; however, trial sequential analysis indicated that the cumulative evidence remains inconclusive. Further large-scale studies are suggested to confirm the magnitude of the radiation dose reduction benefit.

Humans

[Meta-analysis: an alternative method in clinical research].

Meta-analysis is a research method which allows for the grouping of results from different studies relating to the same topic. Its main objective is to increase the precision surrounding the original research problem and provide a possibility to answer to different questions. This method has been developed in the areas of physics and the social sciences and has been widely accepted within the medical field. Its main use in medicine is in relation to the evaluation of therapeutic measures, yet its application has extended to the evaluation of diagnostic tests, etiological and prognostic factors. In spite of its development, there are still persisting problems in research difficult to solve because of the heterogeneity of the grouped studies, the identification of the size of the relevant effect and of the application of the results in clinical practice. The growing use of this research method within the medical field calls for its comprehension, as well as the recognition of its advantages and limitations in order for its users to be capable of judging the validity of individual meta-analysis.

Meta-Analysis as Topic

Precision Optimization of Behavioral Activation for Major and Subthreshold Depression: A Meta-Analysis of Exploring Dose-Response Relationships and Moderating Factors.

OBJECTIVE: This meta-analysis evaluated the efficacy of behavioral activation (BA) in adolescents with subthreshold depression (SD) or major depressive disorder (MDD), exploring dose-response relationships and moderating factors. METHOD: We searched PubMed, EMBASE, Web of Science, EBSCO, Scopus, and the Cochrane Library for randomized controlled trials (RCTs) through December 31, 2024. Risk of bias was assessed using RoB-2, and evidence quality with Grading of Recommendations Assessment, Development, and Evaluation (GRADE). Analyses were performed with R, using standardized mean difference (SMD) for continuous variables and meta-regression for dose-response relationships. Subgroup analyses included symptom severity, intervention setting, delivery format, and parental involvement. The primary outcome was the reduction in depressive symptoms (PROSPERO: CRD42023444273). RESULTS: A total of 14 studies were included (11 RCTs meta-analyzed, comprising 572 participants). BA demonstrated a moderate effect size compared to treatment-as-usual (SMD = -0.42) and a large effect size compared to no-treatment controls (SMD = -0.87). BA was more effective for mild depressive symptoms (SMD = -0.93) than severe symptoms (SMD = -0.43), with significant efficacy in university settings (SMD = -0.94). Intervention without parental involvement exhibited significantly larger effects than those with parental participation (SMD = -0.94 vs -0.38; p < .0001), although this finding was likely confounded by age, symptom severity, and intervention setting. BA moderately improved both behavioral activation levels and functioning (SMD = 0.49). CONCLUSION: Short-term, school-based BA is significantly beneficial for older adolescents with mild depressive symptoms. Findings provide practical guidance for optimizing BA implementation and highlight directions for future research, including the need for larger sample sizes, standardized follow-up assessments, and more representative samples. PLAIN LANGUAGE SUMMARY: This meta-analysis evaluated the effectiveness of behavioral activation (BA), a therapeutic approach focused on improving positive activities, in adolescents with subthreshold depression or major depressive disorder. Based on 14 included studies and 572 participants, BA was found to be more effective for subthreshold compared to major depression. These findings suggest a promising role for BA as an early intervention tool in adolescent depression. STUDY REGISTRATION INFORMATION: Precision Optimization of Behavioral Activation for Major and Subthreshold Depression: A Meta-Analysis of Exploring Dose-response Relationships and Moderating Factors; https://www.crd.york.ac.uk/PROSPERO/view/CRD42023444273. DIVERSITY & INCLUSION STATEMENT: We worked to ensure sex and gender balance in the recruitment of human participants. We worked to ensure race, ethnic, and/or other types of diversity in the recruitment of human participants. We worked to ensure that the study questionnaires were prepared in an inclusive way. Diverse cell lines and/or genomic datasets were not available. We actively worked to promote sex and gender balance in our author group.

Humans

The risks of death and of severe nonfatal reactions with high- vs low-osmolality contrast media: a meta-analysis.

Estimates of the risks associated with the use of radiologic contrast agents frequently are based on a subjective review of some of the numerous articles that have been published on the subject. We have chosen instead to synthesize the existing evidence in an objective, quantitative way by statistically combining the data from individual studies through meta-analysis. Although meta-analysis is subject to whatever biases may exist in the underlying data, and may inappropriately pool data from studies with significant differences, the estimates draw proportionately from each original study and, in addition, gain considerable precision owing to the increased amounts of data considered. Using this technique, we analyzed the data from all available original reports appearing since 1980. Crude rates derived from all reports were used to estimate risks with high-osmolality media. Weighted rate differences based on comparative studies only were used in the estimation of the reductions in risk obtainable with low-osmolality media. The risk of death with high-osmolality media was 0.9 per 100,000 uses (95% confidence interval, 0.3-2.6 per 100,000). The difference in risk produced by using low-osmolality media was 0 (95% confidence interval, -1.1 to 1.1 per 100,000). The risk of severe reactions associated with high-osmolality media was 157 per 100,000 uses (95% confidence interval, 144-172 per 100,000). The reduction in risk that can be obtained by the use of low-osmolality media was estimated to be 126 per 100,000 (95% confidence interval, 110-142 per 100,000). This meta-analysis shows that the risk of death is very low with either type of contrast material and that there is no difference between them. Severe nonfatal reactions with high-osmolality media, although more frequent, are still rare; approximately 80% of them can be prevented by using low-osmolality media.

Contrast Media

Meta-analysis in medicine. Where we are and where we want to go.

An epidemiologically impeccable study does not bring answers to all the important questions. A structured and systematic integration of information from different studies of a given problem with a view to answering the original question or bringing additional information is the essence and objective of the meta-analytic approach to health problem solving. Original studies in medicine, being very heterogeneous in nature and structure require not only a quantitative approach (as in classical meta-analysis) but also an additional "qualitative meta-analysis" as well. The latter represents not only a systematic accumulation of both information and the characteristics of different studies, but also an assessment of quality, uncertainty, missing data, random error and bias across studies of interest. The greatest challenge of meta-analysis in medicine lies in the integration of the qualitative and quantitative assessment of given information (scoring of quality, weighing of the effect size by quality score, etc.). Meta-analysis in medicine must go beyond a simple pooling of data. It should become the "epidemiology of results of independent studies of a common topic of interest". Further development of meta-analysis in such an expanded way may have an important impact on decision-making in clinical medicine, and in health policies.

Clinical Trials as Topic

Evaluation of Prevalence of Obstetric Violence and its Associated Factors: A Systematic Review and Meta-Analysis.

Obstetric violence (OV) begins with a woman's initial contact with a health institution and can persist throughout pregnancy, labor, and the postpartum period. Despite this, previous research has largely focused on the labor process. This systematic review and meta-analysis aimed to determine the prevalence and associated factors of OV experienced by women during pregnancy, labor, or the postpartum period. We conducted systematic searches in five electronic databases (Web of Science, Scopus, CINAHL Ultimate, MEDLINE Ultimate, and OVID) between April 27 and August 7, 2024. Studies were included if they involved women aged 18 and above who experienced mistreatment, abuse, disrespect, or OV during pregnancy, childbirth, or the postpartum period; employed quantitative cohort, descriptive, or cross-sectional designs; were written in English; reported the prevalence of OV and/or associated factors; and were published between January 1, 2007 and December 31, 2023. Data synthesis involved meta-analysis, meta-regression, and narrative synthesis methods. A total of 41 studies, including 43,977 participants from 17 countries, were included. The meta-analysis revealed that the pooled prevalence of OV was 61.7% (95% CI [0.549, 0.680]; I&#xb2;: 99.258%). The meta-regression analysis showed that variables such as the country of study, income level of countries, study setting, study design, and risk of bias had statistically significant effects on OV. In addition, 40 risk factors and 14 protective factors were identified through narrative synthesis. This highlights the high prevalence of OV and the need to address the associated factors.

Humans

Meta-analysis of clinical trials: summary of an international conference.

An international conference of clinicians, clinical investigators and biostatisticians discussed meta-analysis in relation to clinical trials, i.e. the combination of data from separate studies for the purpose of obtaining information that cannot be derived from the individual studies. Meta-analysis can be a helpful tool for generating hypotheses for future trials, for studying the consistency of trials of the same or similar goals, and for generating more precise estimates of effect. There are still a number of unresolved questions about the methodology and interpretation of meta-analysis. Better and more uniform reporting of primary studies would increase the usefulness of meta-analysis.

Clinical Trials as Topic

Meta-analysis: a tool for medical and scientific discoveries.

Medicine has made increasing use of meta-analysis, largely as a quantitative procedure for combining results of clinical trials. Meta-analysis begins with a comprehensive review of the literature. The next step is a systematic analysis of the quality and content of each study. Finally, results are combined statistically and conclusions are drawn from this new overview of the data. This paper presents a brief historical perspective on the use of meta-analysis in medicine with emphasis on the medical library. The authors conclude that in the future, medical librarians will play a significant role in the application of this useful technique.

History, 20th Century

Association between pulse pressure and markers of cognitive function: a systematic review and meta-analysis.

Our aim was to systematically review and meta-analyse evidence on the association between pulse pressure (PP) and cognitive function using PubMed, PsycInfo, Embase and Scopus (inception-July 2025) publication databases. Studies were included if they reported an association between PP and cognitive function and summarized narratively and by performing fixed-effects meta-analysis. The search identified 4171 publications with 43 studies meeting inclusion criteria. Domains assessed included global cognition, memory, language, attention, executive function, processing speed and visuospatial ability. Meta-analysis suggests a positive association between PP and global cognition, and a negative association with memory in both cross-sectional and longitudinal studies with inconsistent findings from narratively summarized studies. Processing speed, executive function and language negatively associated with PP in cross-sectional studies with limited evidence provided by longitudinal studies or narratively summarized studies. There was limited evidence of an association with attention and visuospatial ability.

Humans

A general parametric approach to the meta-analysis of randomized clinical trials.

Meta-analysis provides a systematic and quantitative approach to the summary of results from randomized studies. Whilst many authors have published actual meta-analyses concerning specific therapeutic questions, less has been published about comprehensive methodology. This article presents a general parametric approach, which utilizes efficient score statistics and Fisher's information, and relates this to different methods suggested by previous authors. Normally distributed, binary, ordinal and survival data are considered. Both the fixed effects and random effects model for treatments are described.

Humans