Table 1 Quality criteria for rating the measurement properties in accordance with Terwee et al. 2007, and deviations from COSMIN criteria for methodological quality
Measurement propertya | Definition | Deviations from COSMIN checklist | Threshold for positive rating |
|---|---|---|---|
Score reliability (single administration) | Classical test theory based estimate of overall proportion of true score variance, calculated from the interitem covariance matrix. | Following Sijtsma et al. 2009, the term “internal consistency” was replaced by single administration reliability. Single administration reliability coefficients were considered to provide information about score reliability. | Reliability coefficient ≥ 0.70. |
Score reliability (test-retest) | Classical test theory based estimate of overall proportion of true score variance, obtained from the correlation between repeated measures with same instrument in stable patients. | None, but single administration and test-retest reliability categories were merged in the measurement properties appraisal. | ICC ≥ 0.70. |
Construct Validity | The degree to which PRO scores are related to scores of other validated measures in a way that is consistent with theories about how the constructs the measures presume to assess, are related. | None. | At least 75% of the results are in accordance with the hypotheses. |
Floor and Ceiling effects | The number of respondents who achieved the lowest or highest possible score. | None. | ≤15% of the respondents achieved the highest or lowest possible score. |
Responsiveness | The extent to which a PROM can detect changes in the construct being measured over time. | Following the ISOQOL recommendations and Revicky et al. 2008, favorable rating for responsiveness required empirical evidence of changes in scores consistent with a priori expectations of researchers; Either evidenced by score improvement following intervention with known efficacy, or score changes in accordance with expectations derived from external anchors of change (e.g. patient-reported changed overall health status). | Standardized change scores of at least moderate magnitude (e.g., ES / SRM ≥ 0.30 in the expected direction if changes were expected). |