Validation study of the Parkinson’s Fatigue Scale in advanced Parkinson’s disease

Figures & data

Table 1 Clinical and socio-demographic characteristics of patients at baseline

Baseline characteristics (n=61)
Age, years (mean ± SD) LL-UL	68.02±7.43 50–81
Sex, male (%)	60.7
Duration of the disease, years (mean ± SD) LL-UL	12.57±5.97 4–37
Marital status
Married/Partnered (%)	77.1
Level of education Basic or lesser (%)	77.0
Employment status (%) Retired Never worked before Off sick Others	78.7 13.0 4.9 3.3
Hoehn & Yahr, median (IQR) Stage 1 (%) Stage 2 (%) Stage 3 (%) Stage 4 (%)	2 (1–2) 44.26 42.62 11.48 1.64
CGI-S (median) Score 1 (%) Score 2 (%) Score 3 (%) Score 4 (%)	3 1.64 8.20 75.41 14.75

Abbreviations: LL, lower limit; UL, upper limit: SD, standard deviation; IQR, interquartile range.

Table 2 Descriptive statistics of measures in the study

Measures	Mean	SD	Min	Max
UPDRS – Motor Examination	30.05	14.06	4	58
UPDRS – Complications	8.62	2.87	3	15
Schwab and England Scale (ON)	69.84	23.77	10	100
Non-Motor Symptoms Scale–Total Score	83.05	32.07	29	167
Cardiovascular (including falls)	2.41	3.53	0	14
Sleep/fatigue	16.87	7.63	0	40
Mood/cognition	15.69	13.93	0	56
Perceptual problems/hallucinations	3.08	5.53	0	25
Attention/memory	5.80	6.11	0	24
Gastrointestinal tract	7.44	6.23	0	24
Urinary	12.44	9.59	0	36
Sexual function	7.80	8.16	0	24
Miscellaneous	11.51	8.68	0	36
Beck Anxiety Inventory	19.77	9.24	0	41
Beck Depression Inventory	18.11	9.34	1	46
Apathy Scale	11.69	6.67	1	24
PDQ-39–Summary Index	46.13	13.81	10.90	85.90
Mobility	66.88	22.31	2.50	100.00
Activities of daily living	54.65	24.48	4.17	95.83
Emotional well-being	47.92	21.70	4.17	100.00
Stigma	20.10	22.61	0	93.75
Social support	18.89	24.49	0	100.00
Cognitions	36.35	20.89	0	93.75
Communication	31.81	24.67	0	100.00
Bodily discomfort	45.69	20.73	0	100.00
Zarit Burden Interview	25.30	13.47	4	64
Levodopa equivalent daily dose	1455.98	456.00	478.00	3110.00

Abbreviations: Max, maximum; Min, minimum; PDQ-39, Parkinson’s Disease Questionnaire-39 items; SD, standard deviation; UPDRS, Unified Parkinson’s Disease Rating Scale.

Table 3 Acceptability data of the Parkinson’s Fatigue Scale

Item	Min	Max	Mean	SD	Median	Floor	Ceiling	Skewness
1. I have to rest during the day	1	5	4.02	1.08	4.00	3.4%	40.7%	−1.07
2. My life is restricted by fatigue	1	5	3.64	1.26	4.00	8.5%	27.1%	−0.80
3. I get tired more quickly	2	5	4.25	0.82	4.00	0.0%	44.1%	−1.09
4. One of my three worst symptoms	1	5	3.63	1.16	4.00	5.1%	25.4%	−0.60
5. I feel completely exhausted	1	5	3.16	1.11	3.00	5.2%	10.3%	−0.08
6. Makes me reluctant to socialize	1	5	3.34	1.31	4.00	12.1%	19.0%	−0.48
7. It takes me longer to do things	1	5	3.80	1.18	4.00	8.6%	27.6%	−1.17
8. I have a feeling of heaviness	1	5	3.74	1.09	4.00	5.2%	24.1%	−0.91
9. If I wasn’t tired, I could do more	1	5	4.24	0.94	4.00	1.7%	45.8%	−1.55
10. Everything I do is an effort	1	5	3.76	0.99	4.00	3.4%	22.0%	−0.83
11. I feel tired for much of the time	1	5	3.92	1.02	4.00	1.7%	30.5%	−0.93
12. I feel totally drained	1	5	2.90	1.28	3.00	16.9%	10.2%	−0.01
13. Difficult coping w/daily activities	1	5	3.71	0.99	4.00	3.4%	17.2%	−0.94
14. Tired but I haven’t done anything	1	5	3.55	1.11	4.00	6.9%	15.5%	−0.85
15. I do less than I would like	1	5	4.00	0.99	4.00	1.7%	36.2%	−0.90
16. Want to lay down wherever I am	1	5	3.12	1.24	3.00	10.3%	15.5%	−0.07
Total score	18	78	58.71	12.43	61.00	1.7%	1.7%	−0.84

Abbreviations: Max, maximum; Min, minimum; SD, standard deviation.

Table 4 Corrected item-total correlations

Item	Coefficient^a
1. I have to rest during the day	0.53
2. My life is restricted by fatigue	0.61
3. I get tired more quickly than others	0.50
4. One of my three worst symptoms	0.78
5. I feel completely exhausted	0.67
6. Makes me reluctant to socialize	0.55
7. It takes me longer to do things	0.76
8. I have a feeling of heaviness	0.57
9. If I wasn’t so tired, I could do more	0.59
10. Everything I do is an effort	0.70
11. I feel tired for much of the time	0.69
12. I feel totally drained	0.52
13. Difficulty coping w/daily activities	0.78
14. Tired but I haven’t done anything	0.84
15. I do less than I would like	0.80
16. I want to lay down wherever I am	0.65

Note: ^aSpearman’s rank correlation coefficient.

Table 5 Correlation between the Parkinson Fatigue Scale and other measures

	Coefficient^a
Unified Parkinson’s Disease Rating Scale III	−0.03
Unified Parkinson’s Disease Rating Scale IV	0.12
Schwab and England Scale (ON)	0.04
Item 4 of the Non-Motor Symptoms Scale^b	0.33
Non-Motor Symptoms Scale – Total Score	0.18
Cardiovascular (including falls)	0.20
Sleep/fatigue	0.21
Mood/apathy	0.08
Perceptual problems/hallucinations	0.15
Attention/memory	0.25
Gastrointestinal tract	0.03
Urinary	0.06
Sexual function	0.01
Miscellaneous	0.05
Beck Anxiety Inventory	0.30
Item 20 of the Beck Depression Inventory^b	0.65
Beck Depression Inventory	0.48
Apathy Scale	0.13
PDQ-39 – Summary Index	0.36
Zarit Burden Interview	0.04
Levodopa equivalent daily dose	0.23

Notes: ^aSpearman’s rank correlation coefficient. ^bFatigue-specific items.

Abbreviations: PDQ-39, Parkinson’s Disease Questionnaire-39 items.

Table 6 Differences in assessments between baseline and follow-up

Total score	Baseline				Follow-up
	Mean	SD	Min	Max	Mean	SD	Min	Max	p-value^a
PFS-16	60.17	11.48	32	78	49.60	14.40	16	76	<0.001
UPDRS III	29.04	13.82	4	55	22.89	11.55	2	44	0.001
UPDRS IV	8.56	2.66	3	13	4.36	2.42	0	11	<0.001
Non-Motor Symptoms Scale	83.83	33.35	29	167	48.13	29.79	3	124	<0.001
Beck Anxiety Inventory	20.12	9.72	0	41	13.60	10.39	1	42	<0.001
Beck Depression Inventory	18.45	9.71	1	46	12.64	10.31	0	49	0.003
Apathy Scale	11.69	6.67	1	24	12.34	6.52	1	25	0.460
PDQ-39	46.74	13.59	10.9	85.9	33.66	16.87	4.49	72.44	<0.001
Zarit Burden Interview	24.27	13.67	4	64	24.40	14.28	1	61	0.603

Note: ^aWilcoxon test.

Abbreviations: PDQ-39, Parkinson’s Disease Questionnaire-39 items; PFS-16, Parkinson’s Fatigue Scale; UPDRS, Unified Parkinson’s Disease Rating Scale.

Table 7 Summary of the clinimetric attributes explored for the PFS-16*

	Brown 2005	Kummer 2011	Hagell 2012	Fu 2017	Ozturk 2018	Çilga 2018	Dagklis 2019	Present 2019
Reference	18	19	20	21	22	23	24	–
Missing data		No		No	No			0.3%
Scaling assumptions			S	S
Feasibility/Acceptability
Floor effect		No	No	No				No
Ceiling effect		No	No	No				No
Skewness					S			S
Structure - Factors	1				1	1		2
Internal Consistency
Cronbach’s alpha	S	S		S	S	S	S	S
Inter-item correlation		S			S			S
Item-total correlation			S	S	S	S		S
Convergent Validity
Fatiga	H		H	H	H	H	H	M/H
UPDRS, HY		M	L	L	L	L/M		L
Depression		H	H	M	L			M
Anxiety		H		M	L			M
Apathy								L
Sleep (ESS)		M			L
Cognition		L	L	L	L
Quality of Life					M		H	M
Correlation or Known-groups validity
Age		L	L	L	L	L		No
Sex								No
PD duration			L	L	L	L		No
Education level				L	L			No
LEDD			L	L	L			L
Sensitivity to change								S

Note: *Test-retest reliability has also been analyzed and found satisfactory in several of these studies.

Abbreviations: UPDRS, Unified Parkinson’s Disease Rating Scale; HY, Hoehn and Yahr staging; ESS, Epworth Sleep Scale; PD, Parkinson’s disease; LEDD, Levodopa equivalent daily dose; S, Satisfactory; L, Low; M, Moderate; H, High.