A pragmatic view on pragmatic trials

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Abstract

Clinical trials have been the main tool used by the health sciences community to test and evaluate interventions. Trials can fall into two broad categories: pragmatic and explanatory. Pragmatic trials are designed to evaluate the effectiveness of interventions in real-life routine practice conditions, whereas explanatory trials aim to test whether an intervention works under optimal situations. Pragmatic trials produce results that can be generalized and applied in routine practice settings. Since most results from exploratory trials fail to be broadly generalizable, the “pragmatic design” has gained momentum. This review describes the concept of pragmatism, and explains in particular that there is a continuum between pragmatic and explanatory trials, rather than a dichotomy. Special focus is put on the limitations of the pragmatic trials, while recognizing the importance for and impact of this design on medical practice.

Translated abstract

Los ensayos clínicos han sido la principal herramienta empleada por la comunidad de las ciencias de la salud para probar y evaluar las intervenciones. Los ensayos se pueden clasificar en dos grandes categorías: pragmáticos y explicatívos. Los ensayos pragmáticos están diseñados para evaluar la eficacia de las intervenciones en situaciones de la práctica rutinaria en la vida real, mientras que los ensayos explicativos tienen como objetivo probar si una intervención funciona en situaciones óptimas. Los ensayos pragmáticos generan resultados que pueden ser generalizables y aplicables en ambientes de la práctica habitual. Dado que la mayor parte de los resultados de los ensayos explicativos han dejado de ser amplíamente generalizables, el “diseño pragmático” ha cobrado fuerza. Esta revisión describe el concepto de pragmatismo y explica, en particular, que más que una dicotomía hay un continuo entre los ensayos pragmáticos y los explicatívos. Se pone especíal atención a las limitaciones de los ensayos pragmáticos, a la vez que se reconoce la importancia y el impacto de este diseño en la práctica médica.

Translated abstract

Les études cliniques ont été le principal outil utilisé dans la communauté scientifique médicale pour tester et évaluer les traitements. Les études se répartissent en deux grandes catégories: les études pragmatiques et les études explicatives. Les études pragmatiques sont conçues pour évaluer l'efficacité des traitements dans des conditions de pratique quotidienne de la vie réelle, alors que les études explicatives ont pour but de tester un traitement en conditions optimales. Les études pragmatiques fournissent des résultats qui peuvent être généralisés et appliqués en pratique quotidienne, ce qui n'est pas le cas pour la plupart des études explicatives, et le «schéma pragmatique» a donc le vent en poupe. Cet article décrit le concept de pragmatisme et explique en particulier qu'il existe un continuum entre les études pragmatiques et explicatives, plutôt qu'une dichotomie, il est porté un regard particulier sur les limites des études pragmatiques, tout en reconnaissant leur importance et leur impact sur la pratique médicale.

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Most cited references 25

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Major outcomes in high-risk hypertensive patients randomized to angiotensin-converting enzyme inhibitor or calcium channel blocker vs diuretic: The Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial (ALLHAT).

(2002)

Antihypertensive therapy is well established to reduce hypertension-related morbidity and mortality, but the optimal first-step therapy is unknown. To determine whether treatment with a calcium channel blocker or an angiotensin-converting enzyme inhibitor lowers the incidence of coronary heart disease (CHD) or other cardiovascular disease (CVD) events vs treatment with a diuretic. The Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial (ALLHAT), a randomized, double-blind, active-controlled clinical trial conducted from February 1994 through March 2002. A total of 33 357 participants aged 55 years or older with hypertension and at least 1 other CHD risk factor from 623 North American centers. Participants were randomly assigned to receive chlorthalidone, 12.5 to 25 mg/d (n = 15 255); amlodipine, 2.5 to 10 mg/d (n = 9048); or lisinopril, 10 to 40 mg/d (n = 9054) for planned follow-up of approximately 4 to 8 years. The primary outcome was combined fatal CHD or nonfatal myocardial infarction, analyzed by intent-to-treat. Secondary outcomes were all-cause mortality, stroke, combined CHD (primary outcome, coronary revascularization, or angina with hospitalization), and combined CVD (combined CHD, stroke, treated angina without hospitalization, heart failure [HF], and peripheral arterial disease). Mean follow-up was 4.9 years. The primary outcome occurred in 2956 participants, with no difference between treatments. Compared with chlorthalidone (6-year rate, 11.5%), the relative risks (RRs) were 0.98 (95% CI, 0.90-1.07) for amlodipine (6-year rate, 11.3%) and 0.99 (95% CI, 0.91-1.08) for lisinopril (6-year rate, 11.4%). Likewise, all-cause mortality did not differ between groups. Five-year systolic blood pressures were significantly higher in the amlodipine (0.8 mm Hg, P =.03) and lisinopril (2 mm Hg, P<.001) groups compared with chlorthalidone, and 5-year diastolic blood pressure was significantly lower with amlodipine (0.8 mm Hg, P<.001). For amlodipine vs chlorthalidone, secondary outcomes were similar except for a higher 6-year rate of HF with amlodipine (10.2% vs 7.7%; RR, 1.38; 95% CI, 1.25-1.52). For lisinopril vs chlorthalidone, lisinopril had higher 6-year rates of combined CVD (33.3% vs 30.9%; RR, 1.10; 95% CI, 1.05-1.16); stroke (6.3% vs 5.6%; RR, 1.15; 95% CI, 1.02-1.30); and HF (8.7% vs 7.7%; RR, 1.19; 95% CI, 1.07-1.31). Thiazide-type diuretics are superior in preventing 1 or more major forms of CVD and are less expensive. They should be preferred for first-step antihypertensive therapy.

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Impact of allocation concealment on conclusions drawn from meta-analyses of randomized trials.

J Pildal, A Hróbjartsson, K Jørgensen … (2007)

Randomized trials without reported adequate allocation concealment have been shown to overestimate the benefit of experimental interventions. We investigated the robustness of conclusions drawn from meta-analyses to exclusion of such trials. Random sample of 38 reviews from The Cochrane Library 2003, issue 2 and 32 other reviews from PubMed accessed in 2002. Eligible reviews presented a binary effect estimate from a meta-analysis of randomized controlled trials as the first statistically significant result that supported a conclusion in favour of one of the interventions. We assessed the methods sections of the trials in each included meta-analysis for adequacy of allocation concealment. We replicated each meta-analysis using the authors' methods but included only trials that had adequate allocation concealment. Conclusions were defined as not supported if our result was not statistically significant. Thirty-four of the 70 meta-analyses contained a mixture of trials with unclear or inadequate concealment as well as trials with adequate allocation concealment. Four meta-analyses only contained trials with adequate concealment, and 32, only trials with unclear or inadequate concealment. When only trials with adequate concealment were included, 48 of 70 conclusions (69%; 95% confidence interval: 56-79%) lost support. The loss of support mainly reflected loss of power (the total number of patients was reduced by 49%) but also a shift in the point estimate towards a less beneficial effect. Two-thirds of conclusions in favour of one of the interventions were no longer supported if only trials with adequate allocation concealment were included.

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Making trials matter: pragmatic and explanatory trials and the problem of applicability

Shaun Treweek, Merrick Zwarenstein (2009)

Randomised controlled trials are the best research design for decisions about the effect of different interventions but randomisation does not, of itself, promote the applicability of a trial's results to situations other than the precise one in which the trial was done. While methodologists and trialists have rightly paid great attention to internal validity, much less has been given to applicability. This narrative review is aimed at those planning to conduct trials, and those aiming to use the information in them. It is intended to help the former group make their trials more widely useful and to help the latter group make more informed decisions about the wider use of existing trials. We review the differences between the design of most randomised trials (which have an explanatory attitude) and the design of trials more able to inform decision making (which have a pragmatic attitude) and discuss approaches used to assert applicability of trial results. If we want evidence from trials to be used in clinical practice and policy, trialists should make every effort to make their trial widely applicable, which means that more trials should be pragmatic in attitude.

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Contributors

Division of Genetics, Department of Medicine, Brigham & Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA; Program in Translational Neuropsychiatrie Genomics, Institute for the Neurosciences, Department of Neurology, Brigham & Women's Hospital, Boston, Massachusetts, USA; Program in Medical and Population Genetics, Broad Institute of Harvard and Massachusetts Institute of Technology, Cambridge, Massachusetts, USA

Journal

Journal ID (nlm-ta): Dialogues Clin Neurosci

Journal ID (pmc): Dialogues Clin Neurosci

Title: Dialogues in Clinical Neuroscience

Publisher: Les Laboratoires Servier (France )

ISSN (Print): 1294-8322

ISSN (Electronic): 1958-5969

Publication date (Print): June 2011

Volume: 13

Issue: 2

Pages: 217-224

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[* ] E-mail: npatsopoulos@ 123456rics.bwh.harvard.edu

Article

DOI: 10.31887/DCNS.2011.13.2/npatsopoulos

PMC ID: 3181997

PubMed ID: 21842619

SO-VID: d254a8b0-571e-4f77-b47b-24093ff7030f

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This is an open-access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by-nc-nd/3.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

A pragmatic view on pragmatic trials Translated title: Una perspectiva pragmática de Ios ensayos pragmáticos Translated title: Un point de vue pragmatique sur les études pragmatiques

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Most cited references 25

Major outcomes in high-risk hypertensive patients randomized to angiotensin-converting enzyme inhibitor or calcium channel blocker vs diuretic: The Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial (ALLHAT).

Impact of allocation concealment on conclusions drawn from meta-analyses of randomized trials.

Making trials matter: pragmatic and explanatory trials and the problem of applicability

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