A subset of patients, who were predicted to be clinically stable, completed the questionnaires again 1 week later (test retest analysis) and a different subset, predicted to have a different clinical status, completed the questionnaires again 3 months after baseline (response to change analysis, RCA).
The test-retest reliability for the total MIDAS score was 0.73, indicating that the MIDAS-M questionnaire is stable; for the five disability questions, the test-retest values ranged from 0.77 to 0.87.
Test-retest reliability in the smaller survey was measured to analyse the degree to which the questionnaire yields stable scores over a short period of time (assuming there is no underlying change).
Test-retest reliability, a measure of the degree to which the questionnaire yields stable scores over a short period of time (assuming there is no underlying change), was measured by the intra-class correlation coefficient (ICC) [ 24, 25].
The QLQ-HCC18 scales correlated with scales measuring similar items in the FACT-Hep and the questionnaire was stable over time with an intra-class correlation score of 0.70 for almost all scales.
Scores of physical well-being, social well-being, emotional well-being, functional well-being, as well as PC subscale scores of FACT questionnaire, were stable during the follow-up period and not statistically different among the three groups (Fig. 4b– f).
This study showed that the test retest reliability of the Swedish version of the LLFDI was very good in healthy older adults with balance deficits and fear of falling, for both the function and the disability components, indicating that the questionnaire is stable over time.
Eighty two clinically stable patients repeated the questionnaires 1 week later (test retest analysis) and 107 others, with an expected change in clinical status, repeated the questionnaires 3 months later (response to change analysis, RCA).
Quality of life has physical, psychological, social and functional domains; although ultra-short and single-item measures have been validated, they are less reliable (stable) than multi-domain questionnaires, and their ambiguity limits their value as screening aids (Sloan et al, 2002).
The test-retest scores showed no significant difference for 26 out of the 28 items, indicating that the questionnaire has achieved stable reliability.
