Table 2.
Feasibility, score distributions, and reliability of the Perform Questionnaire (N = 437)
| Physical limitations | Activities of daily living | Beliefs and attitudes | Global scorea | |
|---|---|---|---|---|
| Items (N) | 3 | 3 | 3 | 12 |
| Mean | 11.5 | 11.7 | 11.3 | 34.8 |
| SD | 4.7 | 3.9 | 4.5 | 12 |
| Time taken for administration, mean (SD) | – | – | – | 8.8 (8.9) |
| Easy or very easy to answer the questionnaire, N (%) | – | – | – | 343 (81.1) |
| Completion rateb, N (%) | 419 (95.88) | 417 (95.42) | 358 (81.92) | 351 (80.32) |
| Range of missing answers, N (%) | 2.5% (item 1)–3.7% (item 2) | 2.3% (item 6)–16.9% (item 8) | 2.3% (item 12)–3.7% (item 9) | 2.3% (items 6,12)–16.9% (item 8) |
| Theoretical rangea | 4–20 | 4–20 | 4–20 | 12–60 |
| Observed rangea | 4–20 | 4–20 | 4–20 | 12–60 |
| Floorc (%) | 8.6 | 2.1 | 6.9 | 1.7 |
| Ceilingd (%) | 4.3 | 0.9 | 1.6 | 0.3 |
| Internal consistency, CA | 0.90 | 0.80 | 0.85 | 0.94 |
| Test–retest reliability among stable patients (N = 64)e | ||||
| Mean score (SD) at visit 1 | 11.9 (4.6) | 11.7 (3.8) | 11.7 (4.4) | 35.5 (12.1) |
| Mean score (SD) at visit 2 | 11.5 (4.3) | 11.5 (3.5) | 11.0 (44.4) | 34.3 (11.5) |
| ICC | 0.77 | 0.76 | 0.84 | 0.83 |
CA Cronbach’s alpha, ICC intraclass correlation coefficient, SD standard deviation
aLow scores indicate worse patient perception of CRF
bPercentage of respondents with no missing data in any of the 12 items
cPercentage of patients with the worst possible score
dPercentage of patients with the best possible score
eStability defined as a change <5 mm in the VAS fatigue between study visits