Gordon H. Guyatt

Bio: Gordon H. Guyatt is an academic researcher from McMaster University. The author has contributed to research in topics: Randomized controlled trial & Evidence-based medicine. The author has an hindex of 231, co-authored 1620 publications receiving 228631 citations. Previous affiliations of Gordon H. Guyatt include Memorial Sloan Kettering Cancer Center & Cayetano Heredia University.

Decision Aids for Prostate Cancer Screening Choice: A Systematic Review and Meta-analysis

Abstract: Importance US guidelines recommend that physicians engage in shared decision-making with men considering prostate cancer screening. Objective To estimate the association of decision aids with decisional outcomes in prostate cancer screening. Data Sources MEDLINE, Embase, PsycINFO, CINAHL, and Cochrane CENTRAL were searched from inception through June 19, 2018. Study Selection Randomized trials comparing decision aids for prostate cancer screening with usual care. Data Extraction and Synthesis Independent duplicate assessment of eligibility and risk of bias, rating of quality of the decision aids, random-effects meta-analysis, and Grading of Recommendations, Assessment, Development and Evaluations rating of the quality of evidence. Main Outcomes and Measures Knowledge, decisional conflict, screening discussion, and screening choice. Results Of 19 eligible trials (12 781 men), 9 adequately concealed allocation and 8 blinded outcome assessment. Of 12 decision aids with available information, only 4 reported the likelihood of a true-negative test result, and 3 presented the likelihood of false-negative test results or the next step if the screening test result was negative. Decision aids are possibly associated with improvement in knowledge (risk ratio, 1.38; 95% CI, 1.09-1.73;I2 = 67%; risk difference, 12.1; low quality), are probably associated with a small decrease in decisional conflict (mean difference on a 100-point scale, −4.19; 95% CI, −7.06 to −1.33;I2 = 75%; moderate quality), and are possibly not associated with whether physicians and patients discuss prostate cancer screening (risk ratio, 1.12; 95% CI, 0.90-1.39;I2 = 60%; low quality) or with men’s decision to undergo prostate cancer screening (risk ratio, 0.95; 95% CI, 0.88-1.03;I2 = 36%; low quality). Conclusions and Relevance The results of this study provide moderate-quality evidence that decision aids compared with usual care are associated with a small decrease in decisional conflict and low-quality evidence that they are associated with an increase in knowledge but not with whether physicians and patients discussed prostate cancer screening or with screening choice. Results suggest that further progress in facilitating effective shared decision-making may require decision aids that not only provide education to patients but are specifically targeted to promote shared decision-making in the patient-physician encounter.

Reflections on meta-analyses involving trials stopped early for benefit: Is there a problem and if so, what is it?:

Abstract: We review controversies associated with randomized controlled trials (RCTs) stopped early for apparent benefit (truncated RCTs or tRCTs) and present our groups' perspective. Long-established theory, simulations and recent empirical evidence demonstrate that tRCTs will on average overestimate treatment effects, and this overestimation may be large, particularly when tRCTs have small number of events. Theoretical considerations and simulations demonstrate that on average, meta-analyses of RCTs with appropriate stopping rules will lead to only trivial overestimation of treatment effects. However, tRCTs will disproportionally contribute to meta-analytic estimates when tRCTs occur early in the sequence of trials with few subsequent studies, publication of nontruncated RCTs is delayed, there is publication bias, or tRCTs result in a 'freezing' effect in which 'correcting' trials are never undertaken. To avoid applying overestimates of effect to clinical decision-making, clinicians should view the results of individual tRCTs with small sample sizes and small number of events with skepticism. Pooled effects from meta-analyses including tRCTs are likely to overestimate effect when there is a substantial difference in effect estimates between the tRCTs and the nontruncated RCTs, and in which the tRCTs have a substantial weight in the meta-analysis despite themselves having a relatively small number of events. Such circumstances call for sensitivity analyses omitting tRCTs.

Reporting of financial and non-financial conflicts of interest by authors of systematic reviews: a methodological survey.

Abstract: Background Conflicts of interest may bias the findings of systematic reviews. The objective of this methodological survey was to assess the frequency and different types of conflicts of interest that authors of Cochrane and non-Cochrane systematic reviews report. Methods We searched for systematic reviews using the Cochrane Database of Systematic Reviews and Ovid MEDLINE (limited to the 119 Core Clinical Journals and the year 2015). We defined a conflict of interest disclosure as the reporting of whether a conflict of interest exists or not, and used a framework to classify conflicts of interest into individual (financial, professional and intellectual) and institutional (financial and advocatory) conflicts of interest. We conducted descriptive and regression analyses. Results Of the 200 systematic reviews, 194 (97%) reported authors9 conflicts of interest disclosures, typically in the main document, and in a few cases either online (2%) or on request (5%). Of the 194 Cochrane and non-Cochrane reviews, 49% and 33%, respectively, had at least one author reporting any type of conflict of interest (p=0.023). Institutional conflicts of interest were less frequently reported than individual conflicts of interest, and Cochrane reviews were more likely to report individual intellectual conflicts of interest compared with non-Cochrane reviews (19% and 5%, respectively, p=0.004). Regression analyses showed a positive association between reporting of conflicts of interest (at least one type of conflict of interest, individual financial conflict of interest, institutional financial conflict of interest) and journal impact factor and between reporting individual financial conflicts of interest and pharmacological versus non-pharmacological intervention. Conclusions Although close to half of the published systematic reviews report that authors (typically many) have conflicts of interest, more than half report that they do not. Authors reported individual conflicts of interest more frequently than institutional and non-financial conflicts of interest.

Recognizing and investigating iron-deficiency anemia in hospitalized elderly people

Abstract: OBJECTIVE: To determine whether anemia is documented and appropriately investigated for iron deficiency in hospitalized elderly people. DESIGN: Retrospective chart review. SETTING: Medical clinical teaching unit (CTU) in secondary care hospital in Hamilton, Ont. PARTICIPANTS: Consecutive patients 65 years of age or older admitted between April 1992 and March 1993. OUTCOME MEASURES: Proportion of anemic patients for whom documentation was adequate (included in problem list in patient chart) and for whom adequate investigations were performed (measurement of serum ferritin level in anemic patients in whom iron deficiency was suspected, bone-marrow aspiration for those with intermediate probability of iron deficiency after determination of serum ferritin level, and endoscopy of upper or lower gastrointestinal tract, or both, in patients with iron deficiency). RESULTS: Of 183 eligible patients admitted to the CTU 66 (36%) had anemia, in 47 cases (71%) the anemia was documented by house staff or attending physicians. Of the 66 anemic patients 49 had a non-macrocytic anemia of unknown cause: 26 had their serum ferritin level measured, 5 underwent bone-marrow aspiration, and 21 were referred for gastrointestinal endoscopy. Six of eight patients with probable iron deficiency (i.e., a serum ferritin level that was diagnostic [less than 18 micrograms/L] or suggestive [18 to 45 micrograms/L]) underwent endoscopy, two were found to have cancer of the stomach or cecum. Only 26 of the 49 patients had adequate investigation. CONCLUSIONS: Anemia is common among elderly patients in hospital. However, iron deficiency is underrecognized and underinvestigated.

Preferred reporting items for systematic reviews and meta-analyses: the PRISMA statement

Abstract: David Moher and colleagues introduce PRISMA, an update of the QUOROM guidelines for reporting systematic reviews and meta-analyses

Preferred reporting items for systematic reviews and meta-analyses: the PRISMA Statement.

Abstract: Systematic reviews and meta-analyses have become increasingly important in health care. Clinicians read them to keep up to date with their field,1,2 and they are often used as a starting point for developing clinical practice guidelines. Granting agencies may require a systematic review to ensure there is justification for further research,3 and some health care journals are moving in this direction.4 As with all research, the value of a systematic review depends on what was done, what was found, and the clarity of reporting. As with other publications, the reporting quality of systematic reviews varies, limiting readers' ability to assess the strengths and weaknesses of those reviews. Several early studies evaluated the quality of review reports. In 1987, Mulrow examined 50 review articles published in 4 leading medical journals in 1985 and 1986 and found that none met all 8 explicit scientific criteria, such as a quality assessment of included studies.5 In 1987, Sacks and colleagues6 evaluated the adequacy of reporting of 83 meta-analyses on 23 characteristics in 6 domains. Reporting was generally poor; between 1 and 14 characteristics were adequately reported (mean = 7.7; standard deviation = 2.7). A 1996 update of this study found little improvement.7 In 1996, to address the suboptimal reporting of meta-analyses, an international group developed a guidance called the QUOROM Statement (QUality Of Reporting Of Meta-analyses), which focused on the reporting of meta-analyses of randomized controlled trials.8 In this article, we summarize a revision of these guidelines, renamed PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses), which have been updated to address several conceptual and practical advances in the science of systematic reviews (Box 1). Box 1 Conceptual issues in the evolution from QUOROM to PRISMA

Measuring inconsistency in meta-analyses

Abstract: Cochrane Reviews have recently started including the quantity I 2 to help readers assess the consistency of the results of studies in meta-analyses. What does this new quantity mean, and why is assessment of heterogeneity so important to clinical practice? Systematic reviews and meta-analyses can provide convincing and reliable evidence relevant to many aspects of medicine and health care.1 Their value is especially clear when the results of the studies they include show clinically important effects of similar magnitude. However, the conclusions are less clear when the included studies have differing results. In an attempt to establish whether studies are consistent, reports of meta-analyses commonly present a statistical test of heterogeneity. The test seeks to determine whether there are genuine differences underlying the results of the studies (heterogeneity), or whether the variation in findings is compatible with chance alone (homogeneity). However, the test is susceptible to the number of trials included in the meta-analysis. We have developed a new quantity, I 2, which we believe gives a better measure of the consistency between trials in a meta-analysis. Assessment of the consistency of effects across studies is an essential part of meta-analysis. Unless we know how consistent the results of studies are, we cannot determine the generalisability of the findings of the meta-analysis. Indeed, several hierarchical systems for grading evidence state that the results of studies must be consistent or homogeneous to obtain the highest grading.2–4 Tests for heterogeneity are commonly used to decide on methods for combining studies and for concluding consistency or inconsistency of findings.5 6 But what does the test achieve in practice, and how should the resulting P values be interpreted? A test for heterogeneity examines the null hypothesis that all studies are evaluating the same effect. The usual test statistic …

Bias in meta-analysis detected by a simple, graphical test

Abstract: Objective: Funnel plots (plots of effect estimates against sample size) may be useful to detect bias in meta-analyses that were later contradicted by large trials. We examined whether a simple test of asymmetry of funnel plots predicts discordance of results when meta-analyses are compared to large trials, and we assessed the prevalence of bias in published meta-analyses. Design: Medline search to identify pairs consisting of a meta-analysis and a single large trial (concordance of results was assumed if effects were in the same direction and the meta-analytic estimate was within 30% of the trial); analysis of funnel plots from 37 meta-analyses identified from a hand search of four leading general medicine journals 1993-6 and 38 meta-analyses from the second 1996 issue of the Cochrane Database of Systematic Reviews . Main outcome measure: Degree of funnel plot asymmetry as measured by the intercept from regression of standard normal deviates against precision. Results: In the eight pairs of meta-analysis and large trial that were identified (five from cardiovascular medicine, one from diabetic medicine, one from geriatric medicine, one from perinatal medicine) there were four concordant and four discordant pairs. In all cases discordance was due to meta-analyses showing larger effects. Funnel plot asymmetry was present in three out of four discordant pairs but in none of concordant pairs. In 14 (38%) journal meta-analyses and 5 (13%) Cochrane reviews, funnel plot asymmetry indicated that there was bias. Conclusions: A simple analysis of funnel plots provides a useful test for the likely presence of bias in meta-analyses, but as the capacity to detect bias will be limited when meta-analyses are based on a limited number of small trials the results from such analyses should be treated with considerable caution. Key messages Systematic reviews of randomised trials are the best strategy for appraising evidence; however, the findings of some meta-analyses were later contradicted by large trials Funnel plots, plots of the trials9 effect estimates against sample size, are skewed and asymmetrical in the presence of publication bias and other biases Funnel plot asymmetry, measured by regression analysis, predicts discordance of results when meta-analyses are compared with single large trials Funnel plot asymmetry was found in 38% of meta-analyses published in leading general medicine journals and in 13% of reviews from the Cochrane Database of Systematic Reviews Critical examination of systematic reviews for publication and related biases should be considered a routine procedure

Global Cancer Statistics 2020: GLOBOCAN Estimates of Incidence and Mortality Worldwide for 36 Cancers in 185 Countries.

Abstract: This article provides an update on the global cancer burden using the GLOBOCAN 2020 estimates of cancer incidence and mortality produced by the International Agency for Research on Cancer. Worldwide, an estimated 19.3 million new cancer cases (18.1 million excluding nonmelanoma skin cancer) and almost 10.0 million cancer deaths (9.9 million excluding nonmelanoma skin cancer) occurred in 2020. Female breast cancer has surpassed lung cancer as the most commonly diagnosed cancer, with an estimated 2.3 million new cases (11.7%), followed by lung (11.4%), colorectal (10.0 %), prostate (7.3%), and stomach (5.6%) cancers. Lung cancer remained the leading cause of cancer death, with an estimated 1.8 million deaths (18%), followed by colorectal (9.4%), liver (8.3%), stomach (7.7%), and female breast (6.9%) cancers. Overall incidence was from 2-fold to 3-fold higher in transitioned versus transitioning countries for both sexes, whereas mortality varied <2-fold for men and little for women. Death rates for female breast and cervical cancers, however, were considerably higher in transitioning versus transitioned countries (15.0 vs 12.8 per 100,000 and 12.4 vs 5.2 per 100,000, respectively). The global cancer burden is expected to be 28.4 million cases in 2040, a 47% rise from 2020, with a larger increase in transitioning (64% to 95%) versus transitioned (32% to 56%) countries due to demographic changes, although this may be further exacerbated by increasing risk factors associated with globalization and a growing economy. Efforts to build a sustainable infrastructure for the dissemination of cancer prevention measures and provision of cancer care in transitioning countries is critical for global cancer control.