Table 6.
Data from the validation studies of the PDSS‐2
| Trenkwalder et al., 2011 | Arnaldi et al., 2016 | Kovács et al., 2016 | Present Study, 2018 | |
|---|---|---|---|---|
| Sample size (n) | 113 | 123 | 537 | 399 |
| Range of item scores covered | All, 0 to 4 | — | — | All, 0 to 4 |
| Data quality–missing values | — | — | 0% | 4.8% |
| Floor effect–total score | — | — | 1.70 | 0.26 |
| Ceiling effect–total score | — | — | 0.20 | 0.26 |
| Skewness–total score | — | — | 0.57 | 1.01 |
| Cronbach's alpha | 0.73 | 0.77 | 0.86 | 0.84 |
| Interitem correlation | — | — | — | 0.05 to 0.65 |
| Item homogeneity index | — | — | 0.49 | 0.27 |
| Item‐total correlation | 0.19 to 0.59 | 0.07 to 0.63 | —a | 0.28 to 0.61 |
| Factor analysis–factors (% variance) | 1 (22.8), or 3 (42.7) | 5 (59.4%) | 1 (28.9), or 3 (38.9) | 4 (57.0) |
| Test‐retest kappaw values (or ICC) | 0.44 to 0.76 | — | — | 0.62 to 0.82 |
| Test‐retest ICC | 0.80 | 0.94 | — | 0.83 |
| Precision (SEM value) | 3.98 | 2.14 | 2.46 | 5.84 |
| Convergent validity (with measures for nocturnal sleep) | >0.50 | — | >0.60 | >0.55 |
| Internal validity | — | — | 0.52 to 0.69 | — |
| Discriminative validity | Yes | — | Yes | Yes |
| Bed partners/roommates | Interview | — | PDSS‐2 by proxy |
a
Available for the three embedded PDSS‐2 domains identified by factor analysis, with the following ranges: Motor symptoms = 0.39 to 0.68; PD symptoms = 0.34 to 0.65; Disturbed sleep = 0.36 to 0.53.