Table VI.

Quality Assessment of studies using SIGN guidelines

SIGN criteria	Chun et al., 2016	Chowers et al., 2015	Bessesen et al., 2013	Hassan et al., 2007	Montecalvo et al., 2001	van rijen et al., 2009	Wassenberg et al., 2011
1. Is the paper an economic study (i.e. assessing the cost effectiveness of something), or is it just a study of costs? REJECT IF THE LATTER IS TRUE.	Yes	Yes	Yes	Yes	Yes	Yes	Yes
2. Is the paper relevant to the key question? Analyse using PICO. IF NO REJECT (give reason below). IF YES complete the checklist.	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Section 1: internal validity
1.1. The study addresses an appropriate and clearly focused question	Yes	Yes	Yes	Yes	Yes	Yes	Yes
1.2. The economic importance of the question is clear	Yes	Yes	Yes	Yes	Yes	Yes	Yes
1.3. The choice of study design is justified	Yes	Yes	Yes	Yes	Yes	Yes	Yes
1.4. All costs that are relevant from the viewpoint of the study are included and are measured and valued appropriately	Yes	Yes	Yes	Yes	Yes	Yes	Yes
1.5. The outcome measures used to answer the study question are relevant to that purpose and are measured and valued appropriately	Yes	Moderate	Yes	Moderate	Yes	Moderate	Moderate
1.6 If discounting of future costs and outcomes is necessary, it has been performed correctly	No	No	No	No	No	No	No
1.7. Assumptions are made explicit and a sensitivity analysis performed	Yes	Yes	No	No	No	Moderate	No
1.8. The decision rule is made explicit and comparisons are made on the basis of incremental costs and outcomes	Yes	Yes	Yes	No	Moderate	Yes	Moderate
1.9. The results provide information of relevance to policy makers	Yes	Yes	Yes	Yes	Yes	Yes	Moderate
Section 2: overall assessment
High	10 (90.9%)	9 (81.8%)	9 (81.8%)	7 (63.6%)	8 (72.7%)	8 (72.7%)	6 (54.5%)
Moderate	0 (0%)	1 (9.1%)	0 (0%)	1 (9.1%)	1 (9.1%)	2 (18.2%)	3 (27.3%)
Low	1 (9.1%)	1 (9.1%)	2 (18.2%)	3 (27.3%)	2 (18.2%)	1 (9.1%)	2 (18.2%)

PICO, Patient or Population Intervention Comparison Outcome.