Introduction
Methods
Study setting & ethical considerations
Participants
Data collection
Long-form 39-item Parkinson’s disease questionnaire (PDQ-39)
Short-form eight-item Parkinson’s disease questionnaire (PDQ-8)
Statistical analyses
I. Description
II. Exploratory factor analysis
III. Reliability
IV. Validity
Results
Baseline characteristics
Characteristics | Value |
---|---|
Age
(yr)
| |
Mean (SD) | 61.3 (11.0) |
Gender
NO. (%)
| |
Female | 25 (21.9) |
Male | 89 (78.1) |
Level of Education
NO. (%)
| |
Illiterate | 4 (3.5) |
Primary and/or Secondary | 32 (28.3) |
High School/Diploma | 34 (30.1) |
College and/or University | 43 (38.1) |
Duration of Disease
(yr)
| |
Mean (SD) | 6.3 (5.1) |
Co-morbidities
NO. (%)
| |
Depression | 25 (22.3) |
Cardiovascular Disease | 19 (17.1) |
Hypertension | 18 (16.1) |
Diabetes | 15 (13.5) |
Osteoarthritis | 10 (9.0) |
UPDRS Score
| |
Mean (SD) | 1.8 (2.0) |
Part I-mental | 11.3 (7.7) |
Part II-ADL | 14.7 (9.6) |
Part III-motor | 3.4 (2.8) |
Part IV-complications | 31.3 (18.1) |
Total | |
Hoehn & Yahr Stage
| |
Mean (SD) | 1.9 (0.9) |
Schwab and England activities of daily living score
(%)
| |
Mean (SD) | 81.7 (17.7) |
Daily levodopa dose
(mg)
| |
Mean (SD) | 850 (495) |
Duration of levodopa administration
(yr)
| |
Mean (SD) | 4.6 (4.5) |
Exploratory factor analysis
Internal consistency
Scale | Item | Spearman Rho | Corrected correlation |
Cronbach's α if item deleted
|
---|---|---|---|---|
Mobility
| Q1 | 0.648 | 0.674 | 0.916 |
Q2 | 0.722 | 0.743 | 0.913 | |
Q3 | 0.818 | 0.777 | 0.910 | |
Q4 | 0.842 | 0.773 | 0.910 | |
Q5 | 0.719 | 0.677 | 0.915 | |
Q6 | 0.719 | 0.649 | 0.917 | |
Q7*
| 0.768 | 0.757 | 0.911 | |
Q8 | 0.742 | 0.767 | 0.910 | |
Q9 | 0.606 | 0.566 | 0.921 | |
Q10 | 0.704 | 0.672 | 0.916 | |
PDQ-8-1
| 0.832 | - | Total = 0.922 (95% CI: 0.899-0.942) | |
Activity of daily living (ADL)
| Q11 | 0.748 | 0.773 | 0.858 |
Q12*
| 0.814 | 0.804 | 0.852 | |
Q13 | 0.857 | 0.767 | 0.858 | |
Q14 | 0.675 | 0.474 | 0.906 | |
Q15 | 0.738 | 0.707 | 0.867 | |
Q16 | 0.697 | 0.740 | 0.863 | |
PDQ-8-2
| 0.763 | - | Total = 0.888 (95% CI: 0.852-0.917) | |
Emotional well being
|
Q17*
| 0.764 | 0.665 | 0.820 |
Q18 | 0.618 | 0.587 | 0.834 | |
Q19 | 0.738 | 0.736 | 0.807 | |
Q20 | 0.604 | 0.512 | 0.848 | |
Q21 | 0.800 | 0.695 | 0.813 | |
Q22 | 0.764 | 0.623 | 0.828 | |
PDQ-8-3
| 0.758 | - | Total = 0.850 (95% CI: 0.803-0.889) | |
Stigma
| Q23 | 0.815 | 0.717 | 0.821 |
Q24 | 0.705 | 0.530 | 0.891 | |
Q25*
| 0.857 | 0.801 | 0.787 | |
Q26 | 0.874 | 0.803 | 0.783 | |
PDQ-8-8
| 0.831 | - | Total = 0.862 (95% CI: 0.815-0.899) | |
Social support
|
Q27*
| 0.853 | 0.408 | 0.745 |
Q28 | 0.660 | 0.543 | 0.505 | |
Q29 | 0.566 | 0.598 | 0.521 | |
PDQ-8-4
| 0.680 | - | Total = 0.675 (95% CI: 0.556-0.766) | |
Cognition
| Q30 | 0.645 | 0.334 | 0.696 |
Q31*
| 0.689 | 0.575 | 0.540 | |
Q32 | 0.699 | 0.568 | 0.542 | |
Q33 | 0.680 | 0.393 | 0.656 | |
PDQ-8-5
| 0.668 | - | Total = 0.677 (95% CI: 0.568-0.764) | |
Communication
| Q34 | 0.833 | 0.424 | 0.691 |
Q35*
| 0.727 | 0.579 | 0.413 | |
Q36 | 0.584 | 0.518 | 0.590 | |
PDQ-8-6
| 0.649 | - | Total = 0.662 (95% CI: 0.539-0.757) | |
Bodily discomfort
|
Q37*
| 0.809 | 0.520 | 0.458 |
Q38 | 0.813 | 0.477 | 0.524 | |
Q39 | 0.583 | 0.383 | 0.640 | |
PDQ-7
| 0.806 | - | Total = 0.646 (95% CI: 0.516-0.745) |
Item | Spearman Rho | Corrected Correlation |
Cronbach's α if Item Deleted
|
---|---|---|---|
PDQ-8-Q1
| 0.688 | 0.457 | 0.710 |
PDQ-8-Q2
| 0.547 | 0.349 | 0.740 |
PDQ-8-Q3
| 0.697 | 0.541 | 0.691 |
PDQ-8-Q4
| 0.494 | 0.483 | 0.708 |
PDQ-8-Q5
| 0.462 | 0.401 | 0.720 |
PDQ-8-Q6
| 0.506 | 0.486 | 0.707 |
PDQ-8-Q7
| 0.623 | 0.523 | 0.697 |
PDQ-8-Q8
| 0.468 | 0.330 | 0.733 |
Criterion validity
Scale/Variable | PDQ-39 | PDQ-8 | ||
---|---|---|---|---|
Spearman Rho | P-value | Spearman Rho | P-value | |
Age
| .078 | 0.407 | 0.024 | 0.803 |
Duration of disease
| 0.396 |
<0.001*
| 0.342 |
<0.001*
|
UPDRS score
| ||||
Part I-mental | 0.572 |
<0.001*
| 0.607 |
<0.001*
|
Part II-ADL | 0.653 |
<0.001*
| 0.613 |
<0.001*
|
Part III-motor | 0.447 |
<0.001*
| 0.386 |
<0.001*
|
Part IV-complications | 0.275 |
0.003*
| 0.288 |
0.002*
|
Total | 0.635 |
<0.001*
| 0.591 |
<0.001*
|
Hoehn & Yahr stage
| 0.442 |
<0.001*
| 0.376 |
<0.001*
|
Schwab & England ADL scale
| -0.598 |
<0.001*
| -0.503 |
<0.001*
|
Daily levodopa dose
| 0.313 |
0.001*
| 0.270 |
0.004*
|
Duration of levodopa administration
| 0.302 |
0.001*
| 0.258 |
0.006*
|
Discussion
NO. | Author, year | Sample size | Language | Cronbach’s alpha | Internal consistency (item-to-scale) |
---|---|---|---|---|---|
1 | Katsarou et al., 2004[10] | 228 | Greek | 0.72 | - |
2 |
Martines-Martin et al., 2004
| 64 (patient) | Spanish | 0.842-0.843 | - |
59 (caregiver) | |||||
3 | Tan et al., 2004[9] | 88 | English (in Singapore) | 0.75 | - |
4 | Tan et al., 2007[27] | 104 (English) | English and Chinese | 0.81 | 0.44-0.68 |
79 (Chinese) | 0.87 | ||||
5 | Jenkinson & Fitzpatrick, 2007[7] | 812 | English (USA), English (Canada), Spanish, Italian, Japanese | 0.73-0.88 | 0.28-0.94 |
6 | Franchignoni et al., 2008[24] | 200 | Italian | 0.72 | 0.24-0.59 |
7 | Huang et al., 2011[28] | 100 | Chinese (Taiwan) | 0.81 | 0.37-0.76 |
8 | Dal Bello-Haas et al., 2011[[25] | 24 | English (Canada) | 0.72 | - |
9 |
Present Study, 2013
| 114 | Persian | 0.74 | 0.46-0.70 |