| MEASUREMENT PROPERTIES | |
| Limitations | |
| Observations |
According to a systematic review following the COSMIN criteria, the validation study was found to have “very good” methodological quality of internal consistency, reliability and validity. |
| 1. RELIABILITY | |
| A. Internal Consistency | Tested |
| Cronbach's (Describe) |
Cronbach's alpha for CASQ-QoL 0.966. |
| B. Reliability intraobserver or test-retest | Tested |
| Continuous scores: intraclass correlation coefficient (ICC) Dichotomus: Cohen kappa (Describe) |
ICC for agreement demonstrated a quite good reliability of CASQ-QoL (ICC 0.96). |
| C. Reliability interobserver or Measurement error | Not Tested |
| Standard error of measurement (SEM), smallest detectable change (SDC) or Limits of agreement (LoA) (Describe) |
|
| 2. VALIDITY | |
| A. Content validity: face validity | Tested |
| Expert opinion (relevance and comprehensiveness) (Describe) |
After reviewing the literature, a random sample of 102 patients were interviewed to identify the effect of AS on their daily living. Items pool generated after literature review and patient interviews. In total, 71 items were initially identified including 42 items expressing functional impairment and 29 items for quality of life. After development of the new questionnaire, the instrument was pretested for acceptability and feasibility as a selfadministered questionnaire in a random sample of 30 AS patients. Questionnaire completion was followed by semi-structured interviews to identify any difficulty with instrument completion. |
| B. Construct Validity: Structural validity |
Tested |
| Hypotheses-testing | Tested |
| Cross-cultural validity | Tested |
| Brief Description |
Rasch analysis was used to: 1) remove misfitting items, 2) maximise scale length, 3) eliminate items with overlapping difficulties, and 4) remove gaps along the disability difficulty continuum. CASQ-QoL questionnaire: 10 items displayed adequate fit to the Rasch model. |
| C. Criterion validity | Tested |
| Comparison with a 'gold standard' Continuous scores: correlations, ROC curves Dichotomus: Sensitivity & Specificity (Describe) |
Compared to HAQS and ASQoL, the CASQ-QoL was as well or better correlated with clinical and outcome measures. |