Table 1.

Psychometric characteristics and quality scoring system to evaluate PRO measures (reprinted with adaptation from Terwee et al ⁵⁸)

Characteristic	Description	Positive	Intermediate	Poor
Content Validity	Is the domain of interest comprehensively represented by items in instrument	Clear description of: Measurement aim Target population Concepts measured Item selection in target population	Clear description is lacking or only target population involved or doubtful method	No target population involved
Internal consistency	Are the items in scale measuring same construct	Factor analysis on adequate sample and Cronbach’s alpha between 0.70 and 0.95 per dimension	No factor analysis or doubtful method	Cronbach’s alpha(s) <0.70 or >0.95, despite sound methods
Criterion validity	Are scores on questionnaire related to gold standard	Convincing argument for a gold standard and correlation with gold standard ≥0.70	No convincing arguments for gold standard or doubtful method	Correlation with gold standard <0.70, despite sound method
Construct validity	Do scores on questionnaire relate to other measures in a manner consistent with theoretically derived hypotheses about concepts measured; principal and confirmatory factor analyses	Specific hypotheses and at least 75% of results in support of hypotheses	Doubtful method (eg, no hypotheses)	<75% of hypotheses supported, despite sound methods
Agreement	is the score on repeated measure close (absolute measurement error)	MIC <SDC or MIC outside of LOA or convincing argument that agreement acceptable	Doubtful method or MIC undefined and agreement unacceptable	MIC ≥SDC or MIC outside of LOA, despite sound methods
Reliability	Are patients distinguished from each other, despite relative measurement errors	ICC or weighted Kappa ≥0.70	Doubtful method (eg, time interval not mentioned)	ICC or weighted Kappa <0.70, despite sound methods
Responsiveness	Ability of questionnaire to detect clinically important changes over time	SDC or SDC <MIC or MIC outside LOA or RR >1.96 or AUC ≥0.70	Doubtful design/method	SDC or SDC ≥MIC or MIC equals or inside LOA or RR ≤1.96 or AUC <0.70, despite sound methods
Floor and ceiling effects	No of respondents who achieved lowest and highest possible score	≤15% respondents achieved highest or lowest possible scores	Doubtful design/method	>15% respondents achieved highest or lowest scores despite sound methods
Interpretability	Can one assign qualitative meaning to quantitative scores	Mean/SD scores presented to >4 relevant patient subgroups and MIC defined	Doubtful method or <4 subgroups or MIC undefined	No information found on interpretation

Doubtful design or method=lacking clear description of study design or methods, sample <50 subjects or important methodological design weakness.

AUC, area under the curve; ICC, intraclass correlation; LOA, limits of agreement; MIC, minimally important change; PRO, patient-reported outcome; RR, relative risk; SD, Standard Deviation; SDC, smallest detectable change.