Pragmatische Studien

In Ergänzung zu dem bereits eingestellten Artikel zum Thema "externe Validität" stellen wir hier zwei Leserbriefe aus dem Journal for Clinical Epidemiology (JCE) zur Verfügung, die das Thema "pragmatische Studien" diskutieren.

Deutlich wird, dass es sich bei sogenannten pragmatischen Studien nicht um einen "neuen und anderen" Studientyp handelt, sondern um Studien, die einen besonderen Fokus auf die möglichst breite Anwendbarkeit der Ergebnisse legen, anders als sogenannte explanatorische Studien.

Hinsichtlich der methodischen Validität gelten die allgemein konsentierten Qualitätskriterien für die jeweiligen Studientypen, in diesem Zusammenhang überwiegend RCTs.

Die Freigabe der Texte wurde dem DNEbM durch das JCE erteilt, hierfür bedanken wir uns ganz explizit.

 
It is "the noise of practice"

Jürgen Windeler

published online 22 February 2010.
Volume 63, Issue 6, Page 694 (June 2010)


To the Editor:

I greatly appreciate the work of the pragmatic–explanatory continuum indicator summary (PRECIS) group in framing, structuring, and illustrating the pragmatic–explanatory continuum [1]. In complete support and hopefully correct interpretation, I would like to sharpen the arguments by three short comments: 

  1. It is implicit from the presentation but should be made explicit: there is no such thing as “a pragmatic trial” or “an explanatory trial.” Schwartz and Lellouch's notion of “attitudes” was well chosen, and from the continuum and the illustrative wheel, it is clear that every trial will be positioned somewhere between the extremes and has its pragmatic and explanatory elements.
  2. From the context, it is quite obvious what the authors have in mind while stating "explanatory trials test causal research hypotheses." However, it should be made very clear that answers "that help users choose between options of care" of course are answers to questions of causal relationships—in a way that A changes the risk of B (by an amount of X). It is the "noise of practice" that differs pragmatic from explanatory trials, not the general aim of identifying and quantifying causal effects.
  3. The point mentioned above is of major importance because design follows question and purpose. For causal questions, the randomized trial is the standard and this is not questioned by the term "pragmatic." At least in Germany we are confronted with suggestions that "pragmatic" means the use of other research designs, nonrandomized observational research, or registers. By not mentioning such design aspects as one of the 10 items, the PRECIS-authors seem to share my position that such interpretations are misleading. A clear statement that such suggestions have nothing to do with "pragmatism" in the Schwartz/Lellouch sense would be useful.

Finally, the progress of work should address the use of placebo groups in a "pragmatic trial." There is still much nonsense in "usual" or "standard" care, which can only be identified by placebo-controlled trials. A finding from a "pragmatic trial" that a new treatment is as good as usual care is logically correct but hardly of value for decision makers as long as they cannot be sure that usual care actually is effective. At least in such situations, placebos may have their place also on the pragmatic side of the continuum.

Reference
[1]. Thorpe KE, Zwarenstein M, Oxman AD, Treweek S, Furberg CD, Altman DG, et al. A pragmaticeexplanatory continuum indicator summary (PRECIS): a tool to help trial designers. J Clin Epidemiol. 2009;62:464–75. 
Abstract | Full Text | Full-Text PDF (540 KB) | CrossRef


Pragmatic trials are randomized and may use a placebo

Kevin E. Thorpe, PRECIS writing group
Andrew D. Oxman, PRECIS writing group
Shaun Treweek, PRECIS writing group
Curt D. Furberg, PRECIS writing group

Volume 63, Issue 6, Pages 694-695 (June 2010)
published online 22 February 2010.

In reply:
We would like to thank Prof. Windeler for his thoughtful letter and the editors of the journal for the invitation to respond to his comments.

  1. As we previously said [1], the labels “pragmatic trial” and “explanatory trial” are indeed oversimplifications that imply a simple dichotomy when there is, in fact, a multidimensional continuum. However, the labels are not without value for the planning of a trial. We think that it is important for trialists to consider the "ideal" (or, more specifically, the extremes for each relevant dimension) to make the design decisions that best support their primary goal in doing a trial.
  2. We agree that trials of all kinds are concerned with questions of causal relationships. It is the design decisions with regard to patients, setting, application of treatment, and outcome, among other things, that distinguish the explanatory and pragmatic approaches and thereby affect how the trial results are interpreted and used.
  3. Prof. Windeler is correct that our (and Schwartz and Lellouch's [2]) use of "pragmatism" does not suggest nonrandomized designs. Random allocation is common to the full multidimensional continuum of explanatory and pragmatic trials.


Lastly, Prof. Windeler points out that placebos can be used in both pragmatic and explanatory trials. We agree that the use of a placebo is not a defining feature of explanatory trials. Consequently, we did not say much about this. We do not, however, agree that a finding from a "pragmatic trial" that a new treatment is as good as usual care is never of value to decision makers, when the effects of usual care are uncertain. If the new treatment costs less, and one was confident that it was not worse than usual care, one would likely use it. If it costs more, one would likely not use it unless there was some other advantage, such as less risk of adverse effects. If it costs the same and there were no other advantages, one would likely continue with usual care. Although important uncertainty about the effects of usual care should lead trialists to consider the use of a placebo when their goal is pragmatic, there may sometimes be good reasons for not doing so.


References
[1]. Thorpe KE, Zwarenstein M, Oxman AD, Treweek S, Furberg CD, Altman DG, et al. A pragmatic–explanatory continuum indicator summary (PRECIS): a tool to help trial designers. J Clin Epidemiol. 2009;62:464–475.
Abstract | Full Text | Full-Text PDF (540 KB) | CrossRef

[2]. Schwartz D, Lellouch J. Explanatory and pragmatic attitudes in therapeutical trials. J Chron Dis. 1967;20:637–648[reprinted in J Clin Epidemiol 2009;62:498–504]. 


"Pragmatische Studien" waren 2008 auch ein inhaltlicher Schwerpunkt der jährliche stattfindenden gemeinsamen Tagung des IQWiG mit dem Gesundheitsforschungsrat.

Hierzu sei insbesondere auf den Vortrag von Prof. Norbert Donner-Banzhoff und die zusammenfassende Darstellung der sich anschließenden Diskussion durch Prof. Köbberling verwiesen.

Discussion on the introductory hearings. Part 3: Following the speech of Professor Donner-Banzhoff

Köbberling J.
Z Evid Fortbild Qual Gesundhwes. 2009;103(6):410-1. German. No abstract available. PMID: 19839219 [PubMed - indexed for MEDLINE]
Related citations

Pragmatic trials in a routine care setting

Donner-Banzhoff N.
Z Evid Fortbild Qual Gesundhwes. 2009;103(6):404-9. German. PMID: 19839218 [PubMed - indexed for MEDLINE]
Related citations
 

Externe Validität

Aus Anlass der Übernahme der Leitung des IQWiG durch unseren Past-Präsidenten Prof. Jürgen Windeler starten wir mit dem Thema "Externe Validität".

Der freie Zugang zum Übersichtsartikel aus der ZEFQ wurde dankenswerterweise durch Herrn B. Rolle ermöglicht.


Externe Validität

Jürgen Windeler

Zusammenfassung

Neben der üblichen Qualitätsbewertung von klinischen Studien, die Aspekte der internen Validität betrifft, ist ein anderes Qualitätsmerkmal von Studien, inwieweit ihre Ergebnisse in die Praxis übertragbar sind. Für diesen Aspekt der "externen Validität" gibt es keine ähnlich ausgearbeiteten Prüfinstrumente und Checklisten. Wesentliches Kriterium dieser Qualitätsbewertung ist, ob sich durch die Änderung der Anwendungssituation, die sich entsprechend dem PICO-Schema in verschiedene Aspekte unterteilen lässt, die Effekte einer Therapie ändern. Externe Validität ist also kein Studien-, sondern ein Situationskriterium. Bei der Bewertung geht es nicht darum festzustellen, dass Patienten außerhalb von Studien anders sind als Patienten innerhalb von Studien. Dies ist sicher. Es geht vielmehr darum, ob die Effekte im Sinne eines Unterschieds zwischen zwei Behandlungsgruppen unterschiedlich sind, was man als Effektmodifikation bezeichnet. Generell wird die Beurteilung dadurch erschwert, dass über Effektmodifikationen und deren Einflussfaktoren wenig bekannt ist. Die Bewertung der externen Validität ist daher eher eine Frage fachlichen Ermessens, gestützt auch auf pharmakologische und biologische Informationen.

 
Abstract

It is widely accepted that clinical trials have to be carefully reviewed for internal validity. In addition, aspects of external validity, which is also known as 'generalizability' or 'directness', must be considered. The question of whether the study results can be applied to clinical practice under different conditions than the study itself is of major importance. In contrast to internal validity, external validity has to be viewed as an aspect of the situation, not of a study per se. Assessment of external validity addresses the question of whether effects (comparisons between treatments) are different between patient groups or clinical situations. It is not sufficient and may even not be important whether the patients differ. In epidemiology this situation is well known as 'effect modification.' External validity can be assessed according to the PICO scheme. However, empirical data about effect modifiers are scarce. Consequently, external validity is merely a matter of clinical judgement.

 

 

 

  

Bookmarks
Zuletzt verändert: 23.03.2011