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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.


Papers
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Journal ArticleDOI
TL;DR: In this article, the authors describe how to include considerations about resource utilization when making recommendations according to the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach, and they focus on challenges with rating the confidence in effect estimates (quality of evidence) and incorporating resource use into evidence profiles and Summary of Findings (SoF) tables.

184 citations

Journal ArticleDOI
TL;DR: It is shown that EBM refers to making medical decisions that are consistent with evidence, as a reliable sign, symptom, or mark to enhance reasonableness or truthfulness of some particular claim ("evidence as a guide to truth"), and to serve as a neutral arbiter among competing views.
Abstract: Background: Since the term “evidence-based medicine” (EBM) first appeared in the scientific literature in 1991, the concept has had considerable influence in many parts of the world. Most professional societies, the public, and funding agencies have accepted EBM with remarkable enthusiasm. The concept of evidence-based practice is now applied in management, education, criminology, and social work. Yet, EBM has attracted controversy: its critics allege that EBM uses a narrow concept of evidence and a naive conception of the relationships between evidence, theory, and practice. They also contend that EBM presents itself as a radical restructuring of medical knowledge that discredits more traditional ways of knowing in medicine, largely in the interests of people with a particular investment in the enterprise of large-scale clinical trials. Because EBM proposes a specific relationship between theory, evidence, and knowledge, its theoretical basis can be understood as an epistemological system. Undertaking epistemological inquiry is important because the adoption of a particular epistemological view defines how science is conducted. Methods: In this paper, we challenge this critical view of EBM by examining how EBM fits into broad epistemological debates within the philosophy of science. We consider how EBM relates to some classical debates regarding the nature of science and knowledge. We investigate EBM from the perspective of major epistemological theories (logical-positivism/inductivism, deductivism/falsificationism/theory-ladeness of observations, explanationism/holism, instrumentalism, underdetermination theory by evidence). Results: We first explore the relationship between evidence and knowledge and discuss philosophical support for the main way that evidence is used in medicine: (1) in the philosophical tradition that “rational thinkers respect their evidence,” we show that EBM refers to making medical decisions that are consistent with evidence, (2) as a reliable sign, symptom, or mark to enhance reasonableness or truthfulness of some particular claim (“evidence as a guide to truth”), and (3) to serve as a neutral arbiter among competing views. Our analysis indicates that EBM does not have a rigorous epistemological stance. In fact, EBM enthusiastically draws on all major traditions of philosophical theories of scientific evidence. Conclusions: Our findings indicate that EBM should not be construed as a new scientific or philosophical theory that changes the nature of medicine or our understanding thereof. Rather, we should consider EBM as a continuously evolving heuristic structure for optimizing clinical practice.

184 citations

Journal ArticleDOI
02 Jun 1999-JAMA
TL;DR: It is unsure whether screening relatively young, asymptomatic people at average risk of bowel cancer is likely to do more good than harm, and whether guidelines or recommendations about screening for CRC that might help you are checked.
Abstract: CLINICAL SCENARIO You are a family physician seeing a 47year-old woman and her husband of the same age. They are concerned because a friend recently found out that she had bowel cancer and has urged them both to undergo screening with fecal occult blood tests (FOBTs) because, she says, prevention is much better than the cure she is now undergoing. Both your patients have no family history of bowel cancer and no change in bowel habit. They ask whether you agree that they should be screened. You know that trials of FOBT screening have demonstrated that screening can reduce mortality from colorectal cancer (CRC), but you also recall that FOBTs can have a high false-positive rate that then requires investigation by colonoscopy. You are unsure whether screening these relatively young, asymptomatic people at average risk of bowel cancer is likely to do more good than harm. You decide to check the literature to see if there are any guidelines or recommendations about screening for CRC that might help you.

180 citations

Journal ArticleDOI
24 Oct 2018-BMJ
TL;DR: This guideline aims to promptly and transparently translate potentially practice-changing evidence to usable recommendations for clinicians and patients.
Abstract: ### What you need to know What is the best way to use oxygen therapy for patients with an acute medical illness? A systematic review published in the Lancet in April 2018 found that supplemental oxygen in inpatients with normal oxygen saturation increases mortality.1 Its authors concluded that oxygen should be administered conservatively, but they did not make specific recommendations on how to do it. An international expert panel used that review to inform this guideline. It aims to promptly and transparently translate potentially practice-changing evidence to usable recommendations for clinicians and patients.2 The panel used the GRADE framework and following standards for trustworthy guidelines.3 The panel asked; The panel makes a strong recommendation for maintaining an oxygen saturation of no more than 96% in acutely ill medical patients (upper limit). The panel did not make a recommendation on when to start (the lower limit) for …

180 citations

Journal ArticleDOI
TL;DR: Moderate-quality evidence suggests that daily use of oral finasteride increases hair count and improves patient and investigator assessment of hair appearance, while increasing the risk of sexual dysfunction.
Abstract: Context Androgenetic alopecia is the most common form of alopecia in men. Objective To determine the efficacy and safety of finasteride therapy for patients with androgenetic alopecia. Data Sources MEDLINE, EMBASE, CINAHL, Cochrane Registers, and LILACS were searched for randomized controlled trials reported in any language that evaluated the efficacy and safety of finasteride therapy in comparison to treatment with placebo in adults with androgenetic alopecia. Study Selection and Data Extraction Two reviewers independently evaluated eligibility and collected the data, including assessment of methodological quality (Jadad score). Outcome measures included patient self-assessment, hair count, investigator clinical assessment, global photographic assessment, and adverse effects at short term (≤12 months) and long term (≥24 months). Heterogeneity was explored by testing a priori hypotheses. Data Synthesis Twelve studies fulfilled the eligibility criteria (3927 male patients), 10 of which demonstrated a Jadad score of 3 or more. The proportion of patients reporting an improvement in scalp hair was greater with finasteride therapy than with placebo treatment in the short term (relative risk [RR], 1.81 [95% confidence interval (CI), 1.42-2.32]; I 2 , 64%) and in the long term (RR, 1.71 [95% CI, 1.15-2.53]; I 2 , 16%); both results were considered to have moderate-quality evidence. The number needed to treat for 1 patient to perceive himself as improved was 5.6 (95% CI, 4.6-7.0) in the short term and 3.4 (95% CI, 2.6-5.1) in the long term. Moderate-quality evidence suggested that finasteride therapy increased the mean hair count from baseline in comparison to placebo treatment, expressed as a percentage of the initial count in each individual, at short term (mean difference [MD], 9.42% [95% CI, 7.95%-10.90%]; I 2 , 50%) and at long term (MD, 24.3% [95% CI, 17.92%-30.60%]; I 2 , 0%). Also, the proportion of patients reported as improved by investigator assessment was greater in the short term (RR, 1.80 [95% CI, 1.43-2.26]; number needed to treat, 3.7 [95% CI, 3.2-4.3]; I 2 , 82%) (moderate-quality evidence). Moderate-quality evidence suggested an increase in erectile dysfunction (RR, 2.22 [95% CI, 1.03-4.78]; I 2 , 1%; number needed to harm, 82.1 [95% CI, 56-231]) and a possible increase in the risk of any sexual disturbances (RR, 1.39 [95% CI, 0.99-1.95]; I 2 , 0%). The risk of discontinuing treatment because of sexual adverse effects was similar to that of placebo (RR, 0.88 [95% CI, 0.51-1.49]; I 2 , 5%) (moderate-quality evidence). Conclusion Moderate-quality evidence suggests that daily use of oral finasteride increases hair count and improves patient and investigator assessment of hair appearance, while increasing the risk of sexual dysfunction.

180 citations


Cited by
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Journal ArticleDOI
TL;DR: Moher et al. as mentioned in this paper introduce PRISMA, an update of the QUOROM guidelines for reporting systematic reviews and meta-analyses, which is used in this paper.
Abstract: David Moher and colleagues introduce PRISMA, an update of the QUOROM guidelines for reporting systematic reviews and meta-analyses

62,157 citations

Journal Article
TL;DR: The QUOROM Statement (QUality Of Reporting Of Meta-analyses) as mentioned in this paper was developed to address the suboptimal reporting of systematic reviews and meta-analysis of randomized controlled trials.
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

46,935 citations

Journal ArticleDOI
04 Sep 2003-BMJ
TL;DR: A new quantity is developed, I 2, which the authors believe gives a better measure of the consistency between trials in a meta-analysis, which is susceptible to the number of trials included in the meta- analysis.
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 …

45,105 citations

Journal ArticleDOI
13 Sep 1997-BMJ
TL;DR: Funnel plots, plots of the trials' 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.
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

37,989 citations

Journal ArticleDOI
TL;DR: The GLOBOCAN 2020 estimates of cancer incidence and mortality produced by the International Agency for Research on Cancer (IARC) as mentioned in this paper show that 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 cancer, colorectal (11 4.4%), liver (8.3%), stomach (7.7%) and female breast (6.9%), and cervical cancer (5.6%) cancers.
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.

35,190 citations