Clinical Epidemiology

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BACKGROUND: Risk of the outcome is a mathematical determinant of the absolute treatment benefit of an intervention, yet this can vary substantially within a trial population, complicating the interpretation of trial results. METHODS: We developed risk models using Cox or logistic regression on a set of large publicly available randomized controlled trials (RCTs). We evaluated risk heterogeneity using the extreme quartile risk ratio (EQRR, the ratio of outcome rates in the lowest risk quartile to that in the highest) and skewness using the median to mean risk ratio (MMRR, the ratio of risk in the median risk patient to the average)...

OBJECTIVES: The objective of our article is to show how "quality of evidence" and "imprecision," as they are defined in Grading of Recommendations Assessment, Development, and Evaluation (GRADE) articles, may lead to confusion. We focus only on the context of systematic reviews. STUDY DESIGN AND SETTING: We analyze, with the aid of standard probabilistic and statistical concepts, the concepts of quality of evidence and imprecision as used in the GRADE framework...

Biomedical laboratory experiments routinely use negative controls to identify possible sources of bias, but epidemiologic studies have infrequently used this type of control in their design or measurement approach. Recently, epidemiologists proposed the routine use of negative controls in observational studies and defined the structure of negative controls to detect bias due to unmeasured confounding. We extend this previous study and define the structure of negative controls to detect selection bias and measurement bias in both observational studies and randomized trials...

Standardization of medical care through protocols, order sets, and other tools is increasingly a part of efforts to improve quality. The authors, a physician beginning a new position as director of a community hospital quality program and the chief quality officer of a health care system and director of a course in health care delivery improvement, discuss the benefits and risks of standardization in health care. Recommendations for responsible standardization are presented.

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OBJECTIVES: In randomized controlled clinical trials, continuous outcomes are typically measured at both baseline and follow-up, and mean difference could be estimated using the change scores from baseline or the follow-up scores. This study assesses the impact of using change score vs. follow-up score on the conclusions of meta-analyses. STUDY DESIGN AND SETTING: A total of 63 meta-analyses from six comparative effectiveness reviews were included. The combined mean difference was estimated using a random-effects model, and we also evaluated whether the impact qualitatively varied by alternative random-effects estimates...

This is a confession building on a conversation with David Sackett in 2004 when I shared with him some personal adventures in evidence-based medicine (EBM), the movement that he had spearheaded. The narrative is expanded with what ensued in the subsequent 12 years. EBM has become far more recognized and adopted in many places, but not everywhere, for example, it never acquired much influence in the USA. As EBM became more influential, it was also hijacked to serve agendas different from what it originally aimed for...

BACKGROUND AND OBJECTIVE: Prediction of medical outcomes may potentially benefit from using modern statistical modeling techniques. We aimed to externally validate modeling strategies for prediction of 6-month mortality of patients suffering from traumatic brain injury (TBI) with predictor sets of increasing complexity. METHODS: We analyzed individual patient data from 15 different studies including 11,026 TBI patients. We consecutively considered a core set of predictors (age, motor score, and pupillary reactivity), an extended set with computed tomography scan characteristics, and a further extension with two laboratory measurements (glucose and hemoglobin)...

OBJECTIVE: To develop an evidence-based guideline for Peer Review of Electronic Search Strategies (PRESS) for systematic reviews (SRs), health technology assessments, and other evidence syntheses. STUDY DESIGN AND SETTING: An SR, Web-based survey of experts, and consensus development forum were undertaken to identify checklists that evaluated or validated electronic literature search strategies and to determine which of their elements related to search quality or errors...

Network meta-analysis is an extension of the conventional pair wise meta-analysis to include treatments that have not been compared head to head. It has in recent years caught the interest of clinical investigators in comparative effectiveness research. While allowing a simultaneous comparison of a large number of treatment effects, an inclusion of indirect effects (i.e., estimating effects using treatments that have not been randomized head to head) may introduce bias. This bias occurs from not accounting for covariates differences in the analysis, in a way that allows transfer of causal information across trials...

OBJECTIVE: To assess the effect of antihypertensive treatment on mortality and cardiovascular morbidity in people with diabetes mellitus, at different blood pressure levels. DESIGN: Systematic review and meta-analyses of randomised controlled trials. DATA SOURCES: CENTRAL, Medline, Embase, and BIOSIS were searched using highly sensitive search strategies. When data required according to the protocol were missing but trials were potentially eligible, we contacted researchers, pharmaceutical companies, and authorities...

OBJECTIVES: The Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) is a widely used methodology for the development of clinical practice guideline. Although its reproducibility is good for evaluating the quality of evidence, it has not been tested in context of developing recommendations. The objective of this study was to assess the reproducibility of all GRADE factors that determine the direction and strength of a recommendation among the guideline panel members with limited exposure to GRADE methodology...

OBJECTIVE: To assess differences in estimated treatment effects for mortality between observational studies with routinely collected health data (RCD; that are published before trials are available) and subsequent evidence from randomized controlled trials on the same clinical question. DESIGN: Meta-epidemiological survey. DATA SOURCES: PubMed searched up to November 2014. METHODS: Eligible RCD studies were published up to 2010 that used propensity scores to address confounding bias and reported comparative effects of interventions for mortality...

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INTRODUCTION: For any health intervention, accurate knowledge of both benefits and harms is needed. Systematic reviews often compound poor reporting of harms in primary studies by failing to report harms or doing so inadequately. While the PRISMA statement (Preferred Reporting Items for Systematic reviews and Meta-Analyses) helps systematic review authors ensure complete and transparent reporting, it is focused mainly on efficacy. Thus, a PRISMA harms checklist has been developed to improve harms reporting in systematic reviews, promoting a more balanced assessment of benefits and harms...

OBJECTIVES: We aimed to (1) identify and classify spin (i.e., a description that overstates efficacy and/or understates harm) in systematic reviews and (2) rank spin in abstracts of systematic reviews according to their severity (i.e., the likelihood of distorting readers' interpretation of the results). STUDY DESIGN: First, we used a four-phase consensus process to develop a classification of different types of spin. Second, we ranked the types of spin in abstracts according to their severity using a Q-sort survey with members of the Cochrane Collaboration...

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OBJECTIVES: To examine compliance with International Committee of Medical Journal Editors' (ICMJE) policy on prospective trial registration along with predictors of compliance. STUDY DESIGN AND SETTING: Cross-sectional analysis of all articles reporting trial results published in the six highest-impact general medicine journals in January-June 2014 that were registered in a public trial registry. The main outcome measure was compliance with ICMJE policy. The time frame for trial primary end point ascertainment was used to assess whether retrospective registration could have allowed changing of primary end points following an interim analysis...

Causal inference based on a restricted version of the potential outcomes approach reasoning is assuming an increasingly prominent place in the teaching and practice of epidemiology. The proposed concepts and methods are useful for particular problems, but it would be of concern if the theory and practice of the complete field of epidemiology were to become restricted to this single approach to causal inference. Our concerns are that this theory restricts the questions that epidemiologists may ask and the study designs that they may consider...