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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.