Table 1.

Quality Criteria for Psychometric Properties of Instruments According to Terwee and Associates (2007)

Psychometric property	Quality criteriaa,b
1. Content validity	+A clear description is provided of the measurement aim, the target population, the concepts that are being measured, and the item selection AND target population and (investigators OR experts) were involved in item selection
	? A clear description of above-mentioned aspects is lacking OR only target population involved OR doubtful design or method
	−No target population involvement
	0 No information found on target population involvement
2. Internal consistency	+Factor analyses performed on adequate sample size (7 * # items and ≥100) AND Cronbach's alpha(s) calculated per dimension AND Cronbach's alpha(s) between 0.70 and 0.95
	? No factor analysis OR doubtful design or method
	−Cronbach's alpha(s) <0.70 or >0.95, despite adequate design and method
	0 No information found on internal consistency
3. Criterion validity	+Convincing arguments that gold standard is “gold” AND correlation with gold standard ≥0.70? No convincing arguments that gold standard is “gold” OR doubtful design or method −Correlation with gold standard <0.70, despite adequate design and method
	0 No information found on criterion validity
4. Construct validity	+Specific hypotheses were formulated AND at least 75% of the results are in accordance with these hypotheses
	? Doubtful design or method (e.g., no hypotheses)
	−Less than 75% of hypotheses were confirmed, despite adequate design and methods
	0 No information found on construct validity
5. Reproducibility	+MIC <SDC OR MIC outside the LOA OR convincing arguments that agreement is acceptable
5.1. Agreement	? Doubtful design or method OR (MIC not defined AND no convincing arguments that agreement is acceptable)
	−MIC ≥SDC OR MIC equals or inside LOA, despite adequate design and method
	0 No information found on agreement
5.2. Reliability	+ICC or weighted Kappa ≥0.70
	? Doubtful design or method (e.g., time interval not mentioned)
	−ICC or weighted Kappa <0.70, despite adequate design and method
	0 No information found on reliability
6. Responsiveness	+SDC or SDC <MIC OR MIC outside the LOA OR RRO1.96 OR AUC ≥0.70
	? Doubtful design or method
	−SDC or SDC ≥MIC OR MIC equals or inside LOA OR RR ≤1.96 OR AUC <0.70, despite adequate design and methods
	0 No information found on responsiveness
7. Floor and ceiling effects	+≤15% of the respondents achieved the highest or lowest possible scores
	? Doubtful design or method
	≥15% of the respondents achieved the highest or lowest possible scores, despite adequate design and methods
	0 No information found on interpretation
8. Interpretability	+Mean and SD scores presented of at least four relevant subgroups of patients and MIC defined
	? Doubtful design or method OR less than four subgroups OR no MIC defined
	0 No information found on interpretation

MIC, minimal important change; SDC, smallest detectable change; LOA, limits of agreement; ICC, Intraclass correlation; SD, standard deviation.

^a+ = positive rating; ? = indeterminate rating; − = negative rating; 0 = no information available.

^bDoubtful design or method: lacking of a clear description of the design or methods of the study, sample size smaller than 50 subjects (should be at least 50 in every [subgroup] analysis), or any important methodological weakness in the design or execution of the study.