Sonja Mensch

29 A systematic review of the literature Table 2. (continued) Psychometric property Rating Quality criteria Responsiveness + Correlation with an instrument measuring the same construct > .50 OR at least 75% of the results are in accordance with the hypotheses OR AUC > 0.70 AND correlation with related constructs is higher than with unrelated constructs - Correlation with an instrument measuring the same construct < .50 OR < 75% of the results are in accordance with the hypotheses or AUC < 0.70 OR correlation with related constructs is lower than with unrelated constructs ? Solely correlations determined with unrelated constructs ICC = intraclass correlation coefficient, r = Cohen (weighted) kappa, SDC = smallest detectable change, MIC = minimal important change, MID = minimal important difference, LoA = limits of agreement, DIF = differential item functioning, AUC = area under the receiver operating characteristic curve Rating: + = positive rating, - = negative rating, ? = indeterminate rating Two reviewers independently rated the included studies, after which consensus was obtained. Determining of overall level of evidence of each psychometric property per instrument The method of acquiring evidence for each studied psychometric property of an instrument was based on the strategy of the Cochrane Back Review Group. The overall level of evidence was scored as strong (consistent findings in multiple studies of good methodological quality or in one study of excellent methodological quality), moderate (consistent findings in multiple studies of fair methodological quality or in one study of good methodological quality), limited (one study of fair methodological quality), conflicting (conflicting findings), or unknown (only studies of poor methodological quality) (Dobson et al., 2012; Tulder van, Furlan, Bombardier & Bouter, 2003). RESULTS Search and article selection The results of the literature search and selection of instruments are shown in the flow chart in Figure 1. Quality assessment of methodology and outcomes The investigated psychometric properties, methodological quality of the studies, and rating of their statistical outcomes are listed in Table 4.