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Table 3 Quality criteria for measurement properties adapted from [11] and [15]

From: Measurement properties of adult quality-of-life measurement instruments for eczema: protocol for a systematic review

Property

Rating

Quality criteria

Reliability

  

Internal consistency

+

Cronbach’s alpha(s) ≥ 0.70

?

Dimensionality not known OR Cronbach’s alpha not determined

Cronbach’s alpha(s) < 0.70

+

MIC > SDC OR MIC outside the LOA

?

MIC not defined

MIC ≤ SDC OR MIC equals or inside LOA

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

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

Structural validity (IRT methods applied)

+

Residual correlations among the items after controlling for the dominant factor <0.20 OR Q3′s < 0.37, item scalability >0.30, IRT model fit: G2 > 0.01, no DIF for important subject characteristics (such as age, gender, education): McFadden’s R2 < 0.02

?

Important characteristics not reported

 

Residual correlations among the items after controlling for the dominant factor ≥0.20 OR Q3′s ≥ 0.37, item scalability ≤0.30, IRT model fit: G2 ≤ 0.01, important DIF for important subject characteristics (such as age, gender, education): McFadden’s R2 ≥ 0.02

Hypothesis testing

+

Correlation with an instrument measuring the same construct ≥0.50 OR at least 75% of the results are in accordance with the hypotheses, AND correlation with related constructs is higher than with unrelated constructs

?

Solely correlations determined with unrelated constructs

 

Correlation with an instrument measuring the same construct <0.50 OR <75% of the results are in accordance with the hypotheses OR correlation with related constructs is 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

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

Interpretability

+

MIC calculated and anchor questions clearly described

?

MIC calculated but anchor questions not clearly labelled

 

MIC not reported

  1. MIC: minimal important change, SDC: smallest detectable change, LOA: limits of agreement, ICC: intraclass correlation coefficient, AUC: area under the curve. +positive rating, ? indeterminate rating, −negative rating.