Table 1. SIGN 50 Checklist for RCT Study Design.

Section 1: Internal validity
Each item in Section 1 is to be evaluated using these criteria: 1) Well Covered, 2) Adequately Addressed, 3) Poorly Addressed, and 4) Not Applicable (NA) only for question 1.10.
ITEM	DESCRIPTION
1.1	The study addresses appropriate and clearly focused question.
1.2	The assignment of subjects to treatment groups is randomized.
1.3	An adequate concealment method is used.
1.4	Subjects and investigators are kept blind about allocation.
1.5	The treatment and control groups are similar at the start of the trial.
1.6	The only difference between groups is the treatment under investigation.
1.7	All relevant outcomes are measured in a standard, valid and reliable way.
1.8	What percentage of subjects in each treatment arm dropped out before the study was completed?
1.9	All subjects are analyzed in the groups to which they were randomly allocated (intention to treat analysis).
1.10	Where the study is carried out at more than one site, results are comparable for all sites.

Note that only the RCT in Table 2 was assessed across all quality criteria in SIGN 50. For all CCT study designs in Tables 3 and 4, only criteria 1.1 appeared relevant to the focus of the study and therefore only scored for that criterion. See limitations section of the manuscript for a description of this challenge.

SIGN 50 Network: A Guideline Developer’s Handbook http://www.sign.ac.uk/guidelines/fulltext/50/checklist2.html