Table 2

Quality criteria for measurement properties

Property	Rating	Quality criteria
Reliability
Internal consistency	+	Cronbach’s alpha(s) ≥0.70
	?	Cronbach’s alpha not determined or unidimensionality unknown
	−	Cronbach’s alpha(s) <0.70
Reliability	+	ICC/weighted Kappa ≥0.70 OR Pearson’s r ≥0.80
	?	Neither ICC/weighted Kappa, nor Pearson’s r determined
	−	ICC/weighted Kappa <0.70 OR Pearson’s r <0.80
Measurement error	+	MIC>SDC OR MIC outside the LoA
	?	MIC not defined
	−	MIC≤SDC OR MIC equals or inside LoA
Validity
Content validity	+	All items are considered to be relevant for the construct to be measured, for the target population and for the purpose of the measurement AND the questionnaire is considered to be comprehensive
	?	Not enough information available
	−	Not all items are considered to be relevant for the construct to be measured, for the target population and for the purpose of the measurement OR the questionnaire is considered not to be comprehensive
Construct validity Structural validity	+	Factors should explain at least 50% of the variance
	?	Explained variance not mentioned
	−	Factors explain <50% of the variance
Hypothesis testing	+	Correlations with instruments measuring the same construct≥0.50 OR at least 75% of the results are in accordance with the hypotheses AND correlations with related constructs are higher than with unrelated constructs
	?	Solely correlations determined with unrelated constructs
	−	Correlations with instruments measuring the same construct<0.50 OR <75% of the results are in accordance with the hypotheses OR correlations with related constructs are lower than with unrelated constructs
Cross-cultural validity	+	No differences in factor structure OR no important DIF between language versions
	?	Multiple group factor analysis not applied AND DIF not assessed
	−	Differences in factor structure OR important DIF between language versions
Criterion validity	+	Convincing arguments that gold standard is ‘gold’ AND correlation with gold standard≥0.70
	?	No convincing arguments that gold standard is ‘gold’
	−	Correlation with gold standard<0.70
Responsiveness
Responsiveness	+	Correlation with changes on instruments measuring the same construct≥0.50 OR at least 75% of the results are in accordance with the hypotheses OR AUC≥0.70 AND correlations with changes in related constructs are higher than with unrelated constructs
	?	Solely correlations determined with unrelated constructs
	−	Correlations with changes on instruments measuring the same construct<0.50 OR <75% of the results are in accordance with the hypotheses OR AUC<0.70 OR correlations with changes in related constructs are lower than with unrelated constructs

+, positive rating; −, negative rating; ?, indeterminate rating; AUC, area under the curve; DIF, differential item functioning; ICC, intraclass correlation coefficient; LoA, limits of agreement; MIC, minimal important change; SDC, smallest detectable change.