| MEASUREMENT PROPERTIES | |
| Limitations | >=5 European languages (English) |
| Observations | |
| 1. RELIABILITY | |
| A. Internal Consistency | Tested |
| Cronbach's (Describe) |
Cronbach's alpha=0.87–0.93 (before and after the operation) |
| B. Reliability intraobserver or test-retest | Tested |
| Continuous scores: intraclass correlation coefficient (ICC) Dichotomus: Cohen kappa (Describe) |
ICC=0.91–0.94; The coefficient of reliability was calculated as 6.45 using the Bland and Altman method. |
| C. Reliability interobserver or Measurement error | Tested |
| Standard error of measurement (SEM), smallest detectable change (SDC) or Limits of agreement (LoA) (Describe) |
Minimal important change in cohort studies is aprox 9p and in individual patients aprox 7p. Smallest detectable change is 4points. (Beard, 2015) |
| 2. VALIDITY | |
| A. Content validity: face validity | Tested |
| Expert opinion (relevance and comprehensiveness) (Describe) |
Generating and reducing the number of itmes was performed by interviewing patients. |
| B. Construct Validity: Structural validity |
Tested |
| Hypotheses-testing | Tested |
| Cross-cultural validity | Tested |
| Brief Description |
Data from the OKS were fitted to the Rasch measurement model. The validity of the item scoring functions was examined, also the presence of item bias or differential item functioning, the fit of data to model expectations, and whether or not the item set formed a unidimensional scale, thus giving a valid summed score. After rescoring some items, the scale showed good fit to the Rasch model, with a chi-square interaction statistic of 42.663 (36 df, P = 0.206)(Conaghan, 2007). Factor analysis confirmed the original conceptual basis of the OKS but offered an option to perform additional analyses using pain and functional subscales (Harris, 2013) |
| C. Criterion validity | Not Tested |
| Comparison with a 'gold standard' Continuous scores: correlations, ROC curves Dichotomus: Sensitivity & Specificity (Describe) |
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