How to assess the external validity of therapeutic trials: a conceptual approach

Dekkers, O M; von Elm, E; Algra, A; Romijn, J A; Vandenbroucke, J P (2010). How to assess the external validity of therapeutic trials: a conceptual approach. International journal of epidemiology, 39(1), pp. 89-94. Oxford: Oxford University Press 10.1093/ije/dyp174

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Background External validity of study results is an important issue from a clinical point of view. From a methodological point of view, however, the concept of external validity is more complex than it seems to be at first glance. Methods Methodological review to address the concept of external validity. Results External validity refers to the question whether results are generalizable to persons other than the population in the original study. The only formal way to establish the external validity would be to repeat the study for that specific target population. We propose a three-way approach for assessing the external validity for specified target populations. (i) The study population might not be representative for the eligibility criteria that were intended. It should be addressed whether the study population differs from the intended source population with respect to characteristics that influence outcome. (ii) The target population will, by definition, differ from the study population with respect to geographical, temporal and ethnical conditions. Pondering external validity means asking the question whether these differences may influence study results. (iii) It should be assessed whether the study's conclusions can be generalized to target populations that do not meet all the eligibility criteria. Conclusion Judging the external validity of study results cannot be done by applying given eligibility criteria to a single target population. Rather, it is a complex reflection in which prior knowledge, statistical considerations, biological plausibility and eligibility criteria all have place.

Item Type:

Journal Article (Original Article)


04 Faculty of Medicine > Pre-clinic Human Medicine > Institute of Social and Preventive Medicine (ISPM)

UniBE Contributor:

von Elm, Erik Björn


600 Technology > 610 Medicine & health
300 Social sciences, sociology & anthropology > 360 Social problems & social services




Oxford University Press




Factscience Import

Date Deposited:

04 Oct 2013 14:07

Last Modified:

23 Oct 2019 16:14

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URI: (FactScience: 194893)

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