Table 1

Issues that potentially affect external validity adapted to Rothwell (10).

Heading


Setting of the trial


Healthcare system


Country


Recruitment from primary, secondary, or tertiary care


Selection of participating centers


Selection of participating clinicians


Selection of patients


Eligibility criteria


Exclusion criteria


Random ratio


Patients declining randomization


Characteristics of randomized patients


Baseline clinical characteristics


Severity of disease


Comorbidity


Differences between trial protocol and routine praxis


Trial intervention


Therapeutic or diagnostic advances since the trial was completed


Outcome measures and follow-up


Who measured outcome


Frequency of follow-up


Adequate length of follow-up


Adverse effects of treatment


Completeness of reporting


Selection of trial centers/clinicians


Intensity of trial safety procedures


Fischer et al. BMC Surgery 2012 12:2   doi:10.1186/1471-2482-12-2

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