Table 1 Definition and criteria of good measurement properties, as defined by the COSMIN guidelines [18]

Validity

Structural validity

Degree to which PROM is an adequate reflection of the dimensionality of the construct to be measured

CFA: (CFI or TFLI or comparable measure > 0.95 OR RMSEA < 0.06 OR SRMR < 0.08

Hypotheses testing

Convergent or discriminant: degree to which expected similar domains between measurement tools are in fact similar or degree to which expected different domains between measurement tools are in fact different

 ≥ 75% in accordance with hypothesis

Cross‐cultural validity

Degree to which the performance of the items on a translated or culturally adapted PROM are an adequate reflection of the performance of the original PROM

No important differences found between group factors (such as age, gender, language) in multiple group factor analysis OR no important DIF for group factors (McFadden’s R² < 0.02)

Criterion validity

The degree to which the scores of a PROM are an adequate reflection of a gold standard

Correlation with gold standard ≥ 0.70 OR area under curve (AUC) ≥ 0.70

Reliability

Internal consistency

Degree of interrelatedness among the items in a PROM

Cronbach's alpha ≥ 0.70

Reliability

Proportion of the total variance in the measurements which is due to true different between patients (test–retest, inter–rater, or intra–rater)

Intraclass correlation coefficient (ICC) or weighted Kappa ≥ 0.70

Measurement error

The degree to which the scores of a PROM are attributed to true changes in the construct being measured

Smallest detectable change (SDC) or limits of agreement (LoA) < minimal important change (MIC)

Responsiveness

Responsiveness

The ability of a PROM to detect change over time

The result is in accordance with the hypothesis OR area under curve (AUC) ≥ 0.70