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.

Treatment of acute Achilles tendon ruptures: a systematic overview and metaanalysis.

Abstract: A quantitative systematic review of randomized and quasirandomized trials was conducted to determine the effect of surgical versus conservative treatment of acute Achilles tendon ruptures on rates of rerupture. Secondary outcomes included deep infection rates, return to normal function, and minor complaints. A search of computerized databases was conducted to locate clinical studies published from 1969 to 2000. Additional studies were located through hand searches of major orthopaedic journals, bibliographies of major orthopaedic texts, and personal files. Of the 273 citations initially identified, 11 proved potentially eligible, and six met all eligibility criteria. Three investigators independently graded study quality and abstracted relevant data. Among the studies, surgical repair revealed a significant reduction in the risk of rerupture when compared with conservative treatment. Alternatively, the risk of infection with surgical repair was significantly increased. Pooled analysis of studies did not reveal any difference in the risk of minor complaints or return to normal function between surgical repair and conservatively treated groups. Surgical treatment significantly reduces the risk of Achilles tendon rerupture, but increases the risk of infection, when compared with conservative therapy. Wide confidence intervals around the estimates of risk reduction suggest a large trial is needed to establish risks and benefits.

Questionnaire for measuring oral health-related quality of life in eight- to ten-year-old children.

Abstract: Purpose This study measured oral health-related quality of life for children, which involved the construction of child perceptions questionnaires (CPQs) for ages 6 to 7, 8 to 10, and 11 to 14. The purpose of this study was to present the development and evaluation of the CPQ for 8- to 10-year-olds (CPQ8-10). Methods Questions (N=25) were selected from the CPQ for 11- to 14-year-olds based on the child development literature and input from parents, child psychologist, and teacher of grades 3 and 4. Validity and reliability were evaluated on 68 and 33 children, respectively. Results There was a positive moderate correlation between the CPQ8-10 score and overall well-being rating (R=.45). The level of impact was slightly higher in the orofacial than in the pediatric dentistry group (mean score=19.1 vs 18.4, respectively). Hypotheses concerning the relationship between the CPQ8-10 score and number of decayed surfaces were confirmed with R=.29, and the mean score higher in caries-afflicted than caries-free children (21.1 vs 14.7). The Cronbach's alpha and intraclass correlation coefficients were 0.89 and 0.75, respectively. Conclusions Results suggest good construct validity, internal consistency, reliability and test-retest reliability, but do not demonstrate discriminative validity. This is consistent, however, with theoretical models of oral disease and its consequences. Further research is required, as these are preliminary findings based on convenience sampling.

Users' Guides to the Medical Literature: Essentials of Evidence-Based Clinical Practice

Abstract: "Users' Guide to the Medical Literature: Essentials of Evidence-Based Clinical Practice" will help you develop the core knowledge you need to take control of the medical literature - to uncover the relevant information, assess its validity and determine whether it applies to your patient. The pocketsized Essentials is succinct yet thorough in its exposition of the concepts, making it the ideal text to tote along on the wards. Affordably priced, the book offers: a thorough, comprehensive and clinician-friendly evidence-based medicine toolkit; why framing the right question is so important; how to find and distinguish between strong and weak evidence; what's needed to critically appraise the best evidence; how to weigh the risks and benefits that precede medical management decisions; how to individualize evidence to each patient; and, a CD-ROM to enable intuitive, nonlinear learning experiences in coordination with the text.Also available is the "Manual for Evidence-Based Clinical Practice", which together with "Essentials of Evidence-Based Clinical Practice" provide the most detailed yet clinical-friendly exposition of the concepts necessary to use the medical literature to solve patient problems.

Development of a Health-Related Quality-of-Life Questionnaire (PCOSQ) for Women with Polycystic Ovary Syndrome (PCOS)

Abstract: Objective: To develop a self-administered questionnaire for measuring health-related quality of life (HRQL) in women with polycystic ovary syndrome (PCOS). Methods: We identified a pool of 182 items potentially relevant to women with PCOS through semistructured interviews with PCOS patients, a survey of health professionals who worked closely with PCOS women, and a literature review. One hundred women with PCOS completed a questionnaire in which they told us whether the 182 items were relevant to them and, if so, how important the issue was in their daily lives. We included items endorsed by at least 50% of women in the analysis plus additional items considered crucial by clinicians and an important subgroup of patients in a factor analysis. We chose items for the final questionnaire taking into account both item impact (the frequency and importance of the items) and the results of the factor analysis. Results: Over 50% of the women with PCOS labelled 47 items as important to them. Clinicians chose 5 addi...

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.