Critical Care of the Surgical Patient: Principles of Study Design

2020 ◽  
Author(s):  
Hasan B Alam ◽  
Glenn Wakam ◽  
Michael T. Kemp

Conducting research in an intensive care unit (ICU) is both challenging and rewarding. ICU patients are heterogeneous, complex, and critically ill. Despite these challenges, the ICU is a data-rich research environment that lends itself to cutting-edge clinical investigation. To optimize research outcomes, investigators must carefully consider the principles of study design. This review discusses the most commonly used observational, experimental, and meta-analytic study designs, as well as the theoretical underpinnings of each study type. Published ICU-based research studies are used as examples to highlight key concepts.  This review contains 4 figures, 9 tables, and 33 references. Key words: clinical research, experimental studies, intensive care, meta-analyses, observational studies, study design

Author(s):  
Wolfgang Marx ◽  
Nicola Veronese ◽  
Jaimon T Kelly ◽  
Lee Smith ◽  
Meghan Hockey ◽  
...  

ABSTRACT Numerous observational studies have investigated the role of the Dietary Inflammatory Index (DII®) in chronic disease risk. The aims of this umbrella review and integrated meta-analyses were to systematically synthesize the observational evidence reporting on the associations between the DII and health outcomes based on meta-analyses, and to assess the quality and strength of the evidence for each associated outcome. This umbrella review with integrated meta-analyses investigated the association between the DII and a range of health outcomes based on meta-analyses of observational data. A credibility assessment was conducted for each outcome using the following criteria: statistical heterogeneity, 95% prediction intervals, evidence for small-study effect and/or excess significance bias, as well as effect sizes and P values using calculated random effects meta-analyses. In total, 15 meta-analyses reporting on 38 chronic disease-related outcomes were included, incorporating a total population of 4,360,111 subjects. Outcomes (n = 38) were examined through various study designs including case-control (n = 8), cross-sectional (n = 5), prospective (n = 5), and combination (n = 20) study designs. Adherence to a pro-inflammatory dietary pattern had a significant positive association with 27 (71%) of the included health outcomes (P value < 0.05). Using the credibility assessment, Class I (Convincing) evidence was identified for myocardial infarction only, Class II (Highly suggestive) evidence was identified for increased risk of all-cause mortality, overall risk of incident cancer, and risk of incident site-specific cancers (colorectal, pancreatic, respiratory, and oral cancers) with increasing (more pro-inflammatory) DII score. Most outcomes (n = 31) presented Class III (Suggestive) or lower evidence (Weak or No association). Pro-inflammatory dietary patterns were nominally associated with an increased risk of many chronic disease outcomes. However, the strength of evidence for most outcomes was limited. Further prospective studies are required to improve the precision of the effect size.


2021 ◽  
pp. 216770262110493
Author(s):  
Ioana A. Cristea ◽  
Raluca Georgescu ◽  
John P. A. Ioannidis

We assessed whether the most highly cited studies in emotion research reported larger effect sizes compared with meta-analyses and the largest studies on the same question. We screened all reports with at least 1,000 citations and identified matching meta-analyses for 40 highly cited observational studies and 25 highly cited experimental studies. Highly cited observational studies had effects greater on average by 1.42-fold (95% confidence interval [CI] = [1.09, 1.87]) compared with meta-analyses and 1.99-fold (95% CI = [1.33, 2.99]) compared with largest studies on the same questions. Highly cited experimental studies had increases of 1.29-fold (95% CI = [1.01, 1.63]) compared with meta-analyses and 2.02-fold (95% CI = [1.60, 2.57]) compared with the largest studies. There was substantial between-topics heterogeneity, more prominently for observational studies. Highly cited studies often did not have the largest weight in meta-analyses (12 of 65 topics, 18%) but were frequently the earliest ones published on the topic (31 of 65 topics, 48%). Highly cited studies may offer, on average, exaggerated estimates of effects in both observational and experimental designs.


2021 ◽  
Vol 5 (Supplement_1) ◽  
pp. A842-A842
Author(s):  
Raymond S Douglas ◽  
Ryan Batten ◽  
Rana A Qadeer ◽  
Chris Cameron

Abstract Background: The European Group on Graves’ Orbitopathy (EUGOGO) recommends intravenous methylprednisolone (IVMP) as the first line treatment for moderate-to-severe active thyroid eye disease (TED). While many studies with varying doses of IVMP have reported improvements in inflammation, via clinical activity score (CAS) reduction, the reported improvements in the major progressive outcome of TED, proptosis, vary widely. A reduction in proptosis of ≥2 millimeter (mm) is considered by clinicians and EUGOGO as clinically meaningful. A meta-analysis of existing literature on use of IVMP in TED management, specifically proptosis response, was conducted. Methods: PubMed and Embase were searched for relevant randomized controlled trials (RCTs) and observational studies that included patients with moderate-to-severe active TED receiving treatment with the EUGOGO recommended dose of IVMP (4.5-5g over 12 weeks) from the inception of the databases to date of search (October 2020); regular alerts were established to capture any recent studies. The outcome of interest was change from baseline to week 12 in proptosis in mms. Single-arm meta-analyses were conducted for IVMP using the DerSimonian-Laird random-effects models and forest plots were generated. Pooled means and corresponding 95% confidence intervals (CIs) were calculated. The primary analysis included all identified studies. Sensitivity analyses were conducted based on study design, study characteristics (smoking status), and methodologies (weighted Bayesian meta-analyses based on study design). Results: The search retrieved 12 studies (10 single-center, 8 RCTs, 4 observational studies: 7 from China, 4 from EU, 1 from Turkey), reporting proptosis for 498 patients that were used for the meta-analysis. No placebo-controlled study with the EUGOGO recommended dose of IVMP was found. All studies included patients who were 18 years or older with moderate-to-severe TED and most (n=11) studies included patients with CAS of ≥3. For studies that reported this data, the mean or median (if mean not reported) age ranged from 35 to 52 years and duration of TED symptoms ranged from 4 to 13.6 months. Treatment with IVMP resulted in a reduction of 0.94 mm (95% CI: -1.57 to -0.32) in proptosis from baseline to week 12. The results from the sensitivity analyses were aligned with those from the primary analysis. Conclusions: Among patients with moderate-to-severe TED, this meta-analysis found the EUGOGO-recommended dose of IVMP may result in modest, but not clinically meaningful, improvements in proptosis. However, these results should be interpreted with caution given the paucity of published data and the lack of risk/benefit analyses with glucocorticoid use as compared to the recently FDA-approved therapy, teprotumumab, for the treatment of TED.


2020 ◽  
Author(s):  
Miho Kimachi ◽  
Akira Onishi ◽  
Aran Tajika ◽  
Kimihiko Kimachi ◽  
Toshi Furukawa

Abstract The limited availability of randomized controlled trials (RCTs) in nephrology undermines causal inferences in meta-analyses. Systematic reviews of observational studies have grown more common under such circumstances. We conducted systematic reviews of all comparative observational studies in nephrology from 2006 to 2016 to assess the trends in the past decade. We then focused on the meta-analyses combining observational studies and RCTs to evaluate the systematic differences in effect estimates between study designs using two statistical methods: by estimating the ratio of odds ratios (ROR) of the pooled OR obtained from observational studies versus those from RCTs and by examining the discrepancies in their statistical significance. The number of systematic reviews of observational studies in nephrology had grown by 11.7-fold in the past decade. Among 56 records combining observational studies and RCTs, ROR suggested that the estimates between study designs agreed well (ROR: 1.05, 95% confidence interval: 0.90-1.23). However, almost half of the reviews led to discrepant interpretations in terms of statistical significance. In conclusion, the findings based on ROR might encourage researchers to justify the inclusion of observational studies in meta-analyses. However, caution is needed as the interpretations based on statistical significance were less concordant than those based on ROR.


2021 ◽  
Author(s):  
Isabelle Bray ◽  
Rebecca Reece ◽  
Danielle Sinnett ◽  
Faith Martin ◽  
Robert Hayward

Abstract Background Despite the growing problem of anxiety and depression amongst young people aged 14-24 years living in urban settings, reviews about the role of exposure to green space or nature in preventing anxiety and depression tend to focus on children, adults or sometimes adolescents. This review aims to explore whether, and if so how, exposure to green space reduces the risk of anxiety and depression among young people aged 14-24 living in urban settings.MethodsCINAHL plus, Global Health, MEDLINE, ProQuest: Dissertations and Theses, PsycINFO, Scopus and OpenGrey were searched for research published in English between January 2000 and June 2020, including all study designs. Results 9,208 sources were identified and 48 were included. Experimental studies provided evidence that walking or being in a green space improves mood and state anxiety immediately following the intervention. Observational studies suggest that social interaction, physical activity, and mindfulness mediate the relationship between exposure to green space and mental health. We propose that the absence of noise and traffic and the presence of nature promotes mindfulness and restoration.ConclusionsThis review provides evidence to clinicians about the value of green social prescribing, and to policymakers about the value of bringing the benefits of forests, vegetation and nature into cities, and ensuring that these spaces are accessible and safe for young people to use.


2020 ◽  
Vol 8 (4_suppl3) ◽  
pp. 2325967120S0013
Author(s):  
Drake G. LeBrun ◽  
Mininder S. Kocher ◽  
Keith D. Baldwin ◽  
Neeraj M. Patel

Background: Observational studies are the most commonly employed study designs in the pediatric orthopaedic literature. The differences between observational study designs are important but not widely understood, leading to potential discrepancies between the reported and actual study design. Study design misclassification is associated with a potential for misreporting level of evidence (LOE). Purpose: To determine the degree of study design and LOE misclassification in the pediatric orthopaedic literature. Methods: The Institute for Scientific Information (ISI) Web of Science was queried to identify all pediatric orthopaedic observational studies published from 2014-2017. Reported study design and LOE were recorded for each study. The actual study design and LOE were determined based on established clinical epidemiological criteria by reviewers with advanced epidemiological training. Studies with a discrepancy between reported and actual study design and LOE were identified. The following covariates were recorded for each study: subspecialty, inclusion of a statistician coauthor, sample size, journal, and journal impact factor. Chi-square analysis was used to identify factors associated with study design and LOE misreporting. Results: One thousand articles were screened, yielding 647 observational studies. Three hundred thirty-five publications (52%) did not clearly report a study design in either the abstract or manuscript text. Of those that did, 59/312 (19%) reported the incorrect study design (Figure 1). The largest discrepancy was in the 109 studies that were reported to be case series, among which 30 (27.5%) were actually retrospective cohort studies. Three hundred thirteen publications (48%) did not report a LOE. Of those that did, 95/334 (28%) reported the incorrect LOE (Figure 2). Thirty-three studies (19%) reported a LOE that was higher than the actual LOE and 62 (35%) under-reported the LOE. Conclusion: The majority of observational pediatric orthopaedic studies either did not report a study design or reported the wrong study design. Similarly, the majority of studies did not report or misreported their LOE. Greater epidemiological rigor in classifying and evaluating observational studies is required on the part of investigators, reviewers, and journal editors. [Figure: see text][Figure: see text]


2021 ◽  
Author(s):  
Ioana Cristea ◽  
john Ioannidis ◽  
Raluca Georgescu

We assessed whether the most highly-cited studies in emotion research report larger effect sizes compared with meta-analyses and the largest studies on the same questions. We screened all reports with at least 1000 citations and identified matching meta-analyses for 40 highly-cited observational and 25 highly-cited experimental studies. Observational studies had on average 1.42-fold (95% CI 1.09 to 1.87) larger effects than meta-analyses and 1.99-fold (95% CI 1.33 to 2.99) larger effects than largest studies on the same questions. Experimental studies had fold-increases of 1.29 (95% CI 1.01 to 1.63) versus meta-analyses and 2.02 (95% CI 1.60 to 2.57) versus largest studies. There was substantial between-topic heterogeneity, more prominently for observational studies. Highly-cited studies were uncommonly (12/65 topics, 18%) the largest ones, but they were frequently (31/65 topics, 48%) the earliest published on the topic. Highly-cited studies may offer, on average, exaggerated estimates of effects in both observational and experimental designs.


Author(s):  
Janet L. Peacock ◽  
Philip J. Peacock

This chapter describes the statistical issues involved in performing meta-analyses. It discusses the sources and effects of publication bias and considers ways of correcting for it. It also discusses statistical and clinical heterogeneity and considers how these can be addressed in meta-analyses. Finally, it describes individual patient meta-analysis. Throughout, the chapter includes both trials and observational studies, discussing the challenges that each study design brings and giving examples.


2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Miho Kimachi ◽  
Akira Onishi ◽  
Aran Tajika ◽  
Kimihiko Kimachi ◽  
Toshi A. Furukawa

AbstractThe limited availability of randomized controlled trials (RCTs) in nephrology undermines causal inferences in meta-analyses. Systematic reviews of observational studies have grown more common under such circumstances. We conducted systematic reviews of all comparative observational studies in nephrology from 2006 to 2016 to assess the trends in the past decade. We then focused on the meta-analyses combining observational studies and RCTs to evaluate the systematic differences in effect estimates between study designs using two statistical methods: by estimating the ratio of odds ratios (ROR) of the pooled OR obtained from observational studies versus those from RCTs and by examining the discrepancies in their statistical significance. The number of systematic reviews of observational studies in nephrology had grown by 11.7-fold in the past decade. Among 56 records combining observational studies and RCTs, ROR suggested that the estimates between study designs agreed well (ROR 1.05, 95% confidence interval 0.90–1.23). However, almost half of the reviews led to discrepant interpretations in terms of statistical significance. In conclusion, the findings based on ROR might encourage researchers to justify the inclusion of observational studies in meta-analyses. However, caution is needed, as the interpretations based on statistical significance were less concordant than those based on ROR.


2021 ◽  
pp. 38-80
Author(s):  
Seth J. Schwartz

This chapter covers planning studies; choosing a study design based on one’s hypotheses; the distinctions among association, prediction, and causation and the study designs needed to evaluate each of these levels of relationship; recruiting and retaining hard-to-reach populations; conducting rigorous experimental studies; managing research teams; drawing samples; and conducting secondary data analyses. The material covered in this chapter helps to ensure that authors generate data from rigorous and airtight studies so that the results of such research can be published in the best possible journals. Pitfalls involved in each of the principles covered in the chapter are also discussed, along with the potential consequences of each of the pitfalls.


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