Abstract
Background
Parkinson's disease (PD) is characterized by motor and nonmotor symptoms that progress with time, causing disability. The performance of a disease‐specific, self‐applied tool for assessing disability, the MDS‐UPDRS Part II, is tested against generic and rater‐based rating scales.
Methods
An international, cross‐sectional, observational study was performed. Patients were assessed with the Hoehn and Yahr (HY) and five disability measures: MDS‐UPDRS Part II, Schwab and England Scale (S&E), Clinical Impression of Severity Index‐PD (CISI‐PD) Disability item, Barthel Index (BI), and Rapid Assessment of Disability Scale (RADS). Data analysis included correlation coefficients, Mann‐Whitney and Kruskal‐Wallis tests, and intraclass‐correlation coefficient for concordance.
Results
The sample was composed of 451 patients, 55.2% men, with a mean age of 65.06 years (SD = 10.71). Disability rating scales correlated from |0.75| (CISI‐PD Disability with BI) to 0.87 (MDS‐UPDRS Part II with RADS). In general, MDS‐UPDRS Part II showed high correlation coefficients with clinical variables and satisfactory concordance with the rest of disability measures, with ICC ranging from 0.83 (with BI) to 0.93 (with RADS). All disability rating scales showed statistical significant differences in the sample grouped by sex, age, disease duration, and severity level.
Conclusions
The MDS‐UPDRS Part II showed an appropriate performance to assess disability in PD, even better than some rater‐based, generic or specific, scales applied in this study.
Keywords: Parkinson's disease, disability, assessment, rating scales, MDS‐UPDRS
Disability is defined by the World Health Organization as “the negative result of the dynamic interaction between a person's health condition, environmental factors, and personal factors.”1 It is a frequent consequence of Parkinson's disease (PD),2 and this disease is one of the conditions that contribute most to disability burden, particularly in women and older people.3 Motor features of PD (tremor, bradykinesia, and rigidity) have an impact on functional status, but the presence of nonmotor symptoms such as fatigue, orthostatism, and mood disorders may increase the risk of severe disability and loss of autonomy.4 Patients with PD have a higher prevalence of difficulties in self‐care, mobility, communication, memory and sensory issues, and, in addition, unmet needs related to the activities of daily living (ADL)5, 6 than the general population.
Rating scales used for assessing disability in PD differ in specificity, length, response options, mode of administration, and type of assessed activities: for example ADL, such as walking, dressing or toileting, or instrumental ADL (IADL), such as shopping, meal preparation, housework, and medication and money management. They can be classified as generic versus disease‐specific, or clinician‐based versus self‐assessed. Among the generic scales, the Barthel Index (BI) is widely used, despite the lack of full validation in PD.7 In a review, some PD‐specific scales were recommended for clinical practice and research, such as the Schwab and England Activities of Daily Living scale (S&E) or the Movement Disorders Society‐Unified Parkinson's Disease Rating Scale (MDS‐UPDRS) Part II.7 Examples of clinician‐based rating scales for assessing disability are the BI and the S&E. Between the self‐assessed disability rating scales commonly used in PD, the MDS‐UPDRS Part II and the Self‐Assessment Parkinson's Disease Disability Scale (SPDDS)8 can be found.
The advantages of applying disease‐specific versus generic, or rater‐based versus self‐assessed, disability rating scales are not always evident.7, 9, 10 This situation can present implications for ascertaining the outcomes of drug or rehabilitation interventions.2
The purpose of this study is to test the performance of the self‐assessed, disease‐specific MDS‐UPDRS part II in comparison with generic and rater‐based rating scales for assessing disability in a sample of PD patients.
Methods
Sample
The sample comprised consecutive patients, at any age or disease stage, diagnosed with PD according to international criteria by a neurologist with expertise in movements disorders.11 Exclusion criteria were: (1) parkinsonism other than PD, and (2) having any concomitant condition that impeded or interfered with the assessment of PD. Patients with difficulties in answering written questionnaires were helped by trained staff. Those with scores ≥3 in the MDS‐UPDRS item 1.1 and ≥4 in CISI‐PD Cognition were deemed to have moderate or severe cognitive impairment and were excluded from the analysis.
Patients were recruited from nine neurologic clinics located in Argentina, Chile, Colombia, Cuba, Ecuador, Mexico, and Spain. All of the included patients signed the informed consent before participating in the study. Each participating center obtained approval from their Local Ethics Committee or Institutional Review Board.
Assessments
Patients’ sociodemographic information and historical data of the disease were gathered. For clinical characterization of the PD, the Hoehn and Yahr staging,12 the MDS‐UPDRS,13 and the Clinical Impression of Severity Index for Parkinson's Disease (CISI‐PD)14 were applied. Mood disorders were assessed with the Hospital Anxiety and Depression Scale (HADS)15 with two subscales that included Anxiety (HADS‐A) and Depression (HADS‐D). Health‐related quality of life (HRQoL) was assessed by means of the Parkinson's Disease Questionnaire, 8 items (PDQ‐8),16 and the generic EQ‐5D (index and visual analogue scale, VAS).17
MDS‐UPDRS items were combined to obtain PD cardinal signs and phenotypes: tremor, rigidity, bradykinesia, axial and PIGD scores,18 and complications.
For assessing disability, the following five measures were applied:
S&E, which measures disability using a 0% (vegetative functions, bedridden) to 100% (completely independent) scale with 10% intervals. It has good psychometric properties and is a recommended scale by the International Parkinson and Movement Disorder Society (IPMDS).7
CISI‐PD disability item, rated by the clinician from 0 (normal) to 6 (severely disabled).
MDS‐UPDRS Part II (Motor Experiences of Daily Living),13, 19, 20 composed of 13 patient‐based items rated from 0 (normal) to 4 (severe), with total scores resulting from the sum of the items. It rates impairment (speech, salivation/drooling, chewing/swallowing, tremor and freezing) and difficulties in ADL and IADL (eating, dressing, hygiene, handwriting, doing hobbies/activities, turning in bed, getting out of bed/car/chair, walking, and balance). Cut‐off values were previously established and published20: 0–2, no disability; 3–16, mild; 17–31, moderate; and ≥32, severe. It has good psychometric properties and is a recommended scale by the IPMDS.7
BI, which assesses 10 ADL: feeding, grooming, bathing, dressing, transfers, toileting, bladder and bowel control, walking and stair climbing, with scores from 0 (very dependent) to 100 (very independent). Although it has been widely used in PD patients, it is a “recommended with further validation in PD required” scale.7
Rapid Assessment of Disability Scale (RADS),21 an interview‐based measure with five items extracted from the ADL part of the UPDRS22: speech, cutting food and handling utensils, dressing, hygiene, and walking. Items are scored from 0 (normal) to 4 (severe disability) and a total score results from the sum of the items. It has shown good clinimetric properties.20, 21
All scales were applied in their cross‐culturally adapted and validated Spanish version.
Data Analysis
Sociodemographic and clinical variables were analyzed with descriptive statistics. Variables did not fit normal distribution and, thus, nonparametric statistics (Spearman's rank correlation and Wilcoxon‐Mann‐Whitney and Kruskal‐Wallis tests) were applied to determine associations of disability with clinical and HRQoL rating scales, and with cardinal signs and subtypes. A correlation coefficient ≥0.60 was deemed as strong, with values 0.30–0.59 considered as moderate.23 In the case of the MDS‐UPDRS Part II, we also calculated the Spearman's correlation coefficients for the sample divided in two subgroups, according to the respondent: (1) patient alone, and (2) caregiver alone or caregiver and patient combined. After standardization of scores, the intraclass correlation coefficient (ICC) was calculated as a test of concordance between disability scales.
Mean and standard deviation (SD) of disability rating scales by sex, age, age at onset (≤44, 45–59, and ≥60 years old), disease duration (5‐year intervals: ≤4, 5–9, 10–14, and ≥15 years), HY stages and MDS‐UPDRS parts I, III, and IV severity levels24 were calculated.
Results
The sample was composed of 451 PD patients, 55.2% men, with a mean age of 65.06 years (SD = 10.71). HY stages distribution were as follows: 60 patients (15.3%) were in stage 1; 163 (36.1%) in stage 2; 133 (29.5%) in stage 3; 69 (15.3%) in stage 4; and 17 (3.8%) in stage 5. Mean age at PD onset was 56.55 years (SD = 11.23), and PD duration was 8.66 years (SD = 6.32). Table 1 summarizes sociodemographic, clinical, and HRQoL variables.
Table 1.
Descriptive Statistics of Sociodemographic and Clinical Variables
| Sociodemographic | Mean | SD | Min | Max |
|---|---|---|---|---|
| Age | 65.06 | 10.71 | 22 | 91 |
| Years of education | 11.66 | 5.43 | 0 | 36 |
| Age at onset | 56.55 | 11.23 | 17 | 80 |
| Duration of disease | 8.66 | 6.32 | 0 | 40 |
| LEDD total | 757.59 | 490.19 | 0.00 | 4000.00 |
| PD evaluations | ||||
| MDS‐UPDRS I | 11.10 | 7.04 | 0 | 34 |
| MDS‐UPDRS III | 35.22 | 21.23 | 0 | 97 |
| MDS‐UPDRS IV | 4.64 | 4.97 | 0 | 18 |
| CISI‐PD total | 8.40 | 5.13 | 0 | 21 |
| HADS‐A | 7.32 | 3.97 | 0 | 20 |
| HADS‐D | 6.33 | 4.31 | 0 | 20 |
| PDQ‐8 | 29.18 | 22.11 | 0.00 | 100.00 |
| EQ‐5D index | 0.63 | 0.33 | ‐0.65 | 1.00 |
| EQ‐5D VAS | 64.45 | 23.21 | 0 | 100 |
| Cardinal signs/subtypes/motor complications | ||||
| Tremor score | 7.31 | 6.53 | 0 | 26 |
| Rigidity | 6.23 | 4.03 | 0 | 17 |
| Bradykinesia | 15.44 | 9.05 | 0 | 43 |
| Axial (≠ PIGD score) | 7.23 | 5.48 | 0 | 28 |
| PIGD score | 5.85 | 5.32 | 0 | 20 |
| Dyskinesias | 1.43 | 1.96 | 0 | 8 |
| Fluctuations | 3.20 | 3.49 | 0 | 13 |
| Disability scales | ||||
| Schwab and England | 74.15 | 21.27 | 10 | 100 |
| CISI‐PD disability | 2.52 | 1.65 | 0 | 6 |
| MDS‐UPDRS II | 15.35 | 11.41 | 0 | 49 |
| Barthel index | 85.07 | 22.47 | 0 | 100 |
| RADS | 6.14 | 4.73 | 0 | 20 |
Tremor score: MDS‐UPDRS items 2.10, 3.15a–b, 3.16a–b, 3.17a–e, 3.18; Rigidity: MDS‐UPDRS items 3.3a–e; Bradykinesia: MDS‐UPDRS items 3.4a–b, 3.5a–b, 3.6a–b, 3.7a–b, 3.8a–b, 3.14; Axial (≠ PIGD score): MDS‐UPDRS items 2.1, 2.2, 2.3, 3.1, 3.2, 3.9, 3.13; PIGD score: MDS‐UPDRS items 2.12, 2.13, 3.10, 3.11, 3.12; Dyskinesias: MDS‐UPDRS items 4.1, 4.2; Fluctuations: MDS‐UPDRS items 4.3, 4.4, 4.5, 4.6.
Table 2 shows Spearman's rank correlation coefficients of disability measures and the rest of rating scales. Correlation coefficients between disability rating scales ranged from ǀ0.75ǀ (CISI‐PD Disability with BI) to 0.87 (MDS‐UPDRS Part II with RADS). The lowest correlation coefficients were found between BI and the rest of clinical and QoL measures, ranging from ǀ0.48ǀ (with HADS‐A) to 0.72 (with CISI‐PD total). Regarding cardinal signs and phenotypes, axial and PIGD scores reached the highest correlations with disability scales, with correlation coefficients of 0.88 (axial score) and 0.88 (PIGD) with MDS‐UPDRS Part II. As a whole, MDS‐UPDRS Part II tended to show slightly higher correlation coefficient values than the other scales. ICC ranged between 0.72 (CISI‐PD disability and BI) and 0.93 (MDS‐UPDRS Part II and RADS) (Table 2). The distribution of respondents in MDS‐UPDRS Part II was as follows: 60.3% (272 interviews) by the patient alone, and 39.7% (179) by the patient and caregiver combined or by the caregiver alone. Those patients who needed help for answering from the caregiver were in more advanced stages of the disease, as per the HY (P < 0.0001). MDS‐UPDRS Part II showed significantly higher correlation coefficients with S&E, BI, PDQ‐8, EQ‐5D VAS, and axial no‐PIGD symptoms (P < 0.001) when the respondent was the caregiver or was the patient helped by the caregiver than when the informant was the patient alone (Table 3).
Table 2.
Spearman Correlation Coefficients of Applied Rating Scales and Intraclass Correlation Coefficient Between Disability Rating Scales
| S&E | CISI‐PD Disability | MDS‐UPDRS Part II | Barthel Index | RADS | |
|---|---|---|---|---|---|
| Disability rating scales | |||||
| CISI‐PD disability | −0.85 (0.81) | ||||
| MDS‐UPDRS Part II | −0.82 (0.85) | 0.84 (0.89) | |||
| Barthel index | 0.76 (0.92) | −0.75 (0.72) | −0.77 (0.83) | ||
| RADS | −0.82 (0.85) | 0.83 (0.89) | 0.87 (0.93) | −0.77 (0.84) | — |
| PD evaluations | |||||
| HY | −0.81 | 0.80 | 0.77 | −0.67 | 0.77 |
| MDS‐UPDRS Part I | −0.61 | 0.62 | 0.73 | −0.57 | 0.65 |
| MDS‐UPDRS Part III | −0.70 | 0.73 | 0.75 | −0.62 | 0.78 |
| MDS‐UPDRS Part IV | −0.70 | 0.68 | 0.70 | −0.58 | 0.68 |
| CISI‐PD total | −0.85 | — | 0.85 | −0.72 | 0.82 |
| HADS‐A | −0.45 | 0.47 | 0.53 | −0.48 | 0.48 |
| HADS‐D | −0.55 | 0.56 | 0.61 | −0.51 | 0.55 |
| PDQ‐8 | −0.75 | 0.73 | 0.83 | −0.66 | 0.78 |
| EQ‐5D index | 0.72 | −0.72 | −0.79 | 0.67 | −0.73 |
| EQ‐5D VAS | 0.63 | −0.62 | −0.64 | 0.54 | −0.60 |
| Cardinal signs/subtypes/motor complications | |||||
| Tremor scorea | −0.26 | 0.28 | 0.34 | −0.25 | 0.31 |
| Rigidity | −0.48 | 0.47 | 0.54 | −0.38 | 0.56 |
| Bradykinesia | −0.68 | 0.72 | 0.72 | −0.60 | 0.75 |
| Axial (≠ PIGD score)a | −0.76 | 0.79 | 0.88 | −0.69 | 0.83 |
| PIGD scorea | −0.84 | 0.86 | 0.88 | −0.78 | 0.84 |
| Dyskinesias | −0.49 | 0.44 | 0.46 | −0.34 | 0.44 |
| Fluctuations | −0.70 | 0.69 | 0.71 | −0.60 | 0.68 |
All correlation coefficients are significant, P < 0.001. In parentheses and italic, intraclass correlation coefficients (ICC).
Combined scores include items of the MDS‐UPDRS Part II.
Table 3.
Correlation Coefficients of MDS‐UPDRS Part II with the Rest of Measures According to the Informant
| Patient (n = 272) | Caregiver or Patient and Caregiver (n = 179) | P a | |
|---|---|---|---|
| Disability rating scales | |||
| S&E | −0.76 | −0.87 | 0.0005 |
| CISI‐PD cisability | 0.80 | 0.85 | 0.1 |
| Barthel index | −0.62 | −0.86 | <0.0001 |
| RADS | 0.83 | 0.89 | 0.016 |
| PD evaluations | |||
| HY | 0.71 | 0.78 | 0.10 |
| MDS‐UPDRS I | 0.65 | 0.72 | 0.17 |
| MDS‐UPDRS III | 0.67 | 0.78 | 0.016 |
| MDS‐UPDRS IV | 0.61 | 0.70 | 0.10 |
| CISI‐PD | 0.80 | 0.85 | 0.10 |
| HADS‐ANX | 0.49 | 0.45 | 0.60 |
| HADS‐DEP | 0.56 | 0.55 | 0.88 |
| PDQ‐8 | 0.75 | 0.86 | 0.001 |
| EQ‐5D index | −0.74 | −0.80 | 0.13 |
| EQ‐5D VAS | −0.50 | −0.70 | 0.001 |
Comparison of correlation coefficients, Fisher r‐to‐z transformation test. Bonferroni correction, P < 0.0035.
Disability rating scales scores were significantly different by gender, indicating a worse functional state for women. Older patients, those with longer disease duration, and those in advanced stages of the disease, as measured by HY and MDS‐UPDRS Parts I, III, and IV, also showed significantly worse scores in disability rating scales. No significant differences in disability scores were found in the sample grouped by age at onset (Table 4).
Table 4.
Disability Rating Scales Scores by Groups of Interest
| S&E | CISI‐PD Disability | MDS‐UPDRS II | Barthel Index | RADS | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Mean | SD | Mean | SD | Mean | SD | Mean | SD | Mean | SD | |
| Sex | ||||||||||
| Men | 77.35 | 18.84 | 2.29 | 1.58 | 13.97 | 10.52 | 88.73 | 19.06 | 5.57 | 4.36 |
| Women | 70.20 | 23.37 | 2.82 | 1.70 | 17.04 | 12.24 | 80.54 | 25.41 | 6.83 | 5.07 |
| P a | 0.001 | 0.001 | 0.011 | <0.001 | 0.013 | |||||
| Age | ||||||||||
| ≤66 y.o. | 79.00 | 17.96 | 2.26 | 1.58 | 12.89 | 10.13 | 90.83 | 16.08 | 5.30 | 4.29 |
| 67+ y.o. | 69.10 | 23.22 | 2.80 | 1.69 | 17.90 | 12.11 | 79.07 | 26.33 | 7.01 | 5.01 |
| P a | <0.001 | 0.001 | <0.001 | <0.001 | <0.001 | |||||
| Age at onset | ||||||||||
| ≤44 y.o. | 76.18 | 20.68 | 2.60 | 1.64 | 15.75 | 11.74 | 86.18 | 21.34 | 6.47 | 4.68 |
| 45–59 y.o. | 74.09 | 19.74 | 2.54 | 1.57 | 15.24 | 10.55 | 87.51 | 18.65 | 6.17 | 4.45 |
| ≥60 y.o. | 73.63 | 22.99 | 2.49 | 1.75 | 15.35 | 12.22 | 82.18 | 25.97 | 6.01 | 5.03 |
| P b | 0.659 | 0.831 | 0.796 | 0.497 | 0.528 | |||||
| Disease duration | ||||||||||
| ≤4 years | 88.27 | 10.49 | 1.37 | 1.25 | 7.50 | 7.42 | 96.62 | 8.69 | 3.07 | 3.07 |
| 5–9 years | 73.51 | 20.76 | 2.59 | 1.55 | 15.32 | 9.84 | 84.36 | 23.19 | 6.11 | 4.35 |
| 10–14 years | 68.04 | 18.77 | 3.10 | 1.37 | 19.38 | 9.77 | 82.93 | 19.59 | 7.49 | 4.17 |
| ≥15 years | 55.97 | 23.11 | 3.88 | 1.42 | 25.40 | 12.30 | 66.94 | 29.12 | 10.39 | 4.76 |
| P b | <0.001 | <0.001 | <0.001 | <0.001 | <0.001 | |||||
| HY | ||||||||||
| 1 | 93.33 | 6.10 | 0.77 | 0.86 | 4.20 | 3.96 | 98.12 | 4.86 | 1.78 | 2.49 |
| 2 | 86.63 | 8.69 | 1.58 | 0.99 | 9.72 | 6.45 | 96.56 | 6.63 | 3.75 | 2.38 |
| 3 | 69.10 | 13.57 | 3.27 | 1.05 | 18.11 | 7.67 | 86.92 | 15.78 | 6.60 | 2.76 |
| 4 | 46.38 | 15.34 | 4.42 | 0.99 | 29.20 | 9.69 | 56.30 | 19.26 | 12.75 | 2.98 |
| 5 | 28.82 | 19.65 | 5.12 | 0.93 | 36.65 | 7.66 | 24.12 | 20.10 | 16.18 | 2.58 |
| P b | <0.001 | <0.001 | <0.001 | <0.001 | <0.001 | |||||
| MDS‐UPDRS I levels | ||||||||||
| Mild | 83.90 | 13.87 | 1.75 | 1.33 | 9.20 | 7.15 | 94.66 | 12.21 | 3.84 | 3.35 |
| Moderate | 66.67 | 21.09 | 3.19 | 1.47 | 20.09 | 9.82 | 79.38 | 23.16 | 7.97 | 4.35 |
| Severe | 43.75 | 19.31 | 4.68 | 1.00 | 34.40 | 8.53 | 48.38 | 23.76 | 13.03 | 3.43 |
| P b | <0.001 | <0.001 | <0.001 | <0.001 | <0.001 | |||||
| MDS‐UPDRS III Levels | ||||||||||
| Mild | 85.40 | 12.67 | 1.58 | 1.27 | 8.95 | 7.46 | 95.25 | 10.44 | 3.38 | 2.97 |
| Moderate | 70.33 | 17.78 | 3.13 | 1.31 | 18.00 | 8.54 | 82.87 | 21.00 | 7.55 | 3.74 |
| Severe | 41.41 | 16.80 | 4.58 | 0.92 | 32.83 | 8.25 | 52.50 | 26.02 | 13.06 | 3.37 |
| P b | <0.001 | <0.001 | <0.001 | <0.001 | <0.001 | |||||
| MDS‐UPDRS IV Levels | ||||||||||
| Mild | 85.38 | 14.01 | 1.62 | 1.28 | 9.54 | 7.97 | 94.82 | 11.87 | 3.71 | 3.28 |
| Moderate | 64.36 | 20.01 | 3.47 | 1.38 | 20.26 | 10.48 | 76.28 | 26.86 | 8.37 | 4.51 |
| Severe | 44.77 | 13.55 | 4.32 | 0.96 | 31.07 | 7.75 | 60.57 | 20.44 | 12.05 | 3.13 |
| P b | <0.001 | <0.001 | <0.001 | <0.001 | <0.001 | |||||
Mann‐Whitney test.
Kruskal‐Wallis test.
S&E, Schwab and England scale; CISI‐PD, Clinical Impression of Severity Index for Parkinson's disease; MDS‐UPDRS, Movement Disorders Society—Unified Parkinson's Disease Rating Scale; RADS, Rapid assessment of disability scale; y.o., years old; SD, standard deviation.
Discussion
In this study, the performance of self‐rated MDS‐UPDRS Part II, PD‐specific rating scale for assessing disability, in comparison with other interview‐based, generic, or disease‐specific tools, was analyzed. Accurate assessment of disability in PD is relevant for clinical issues, such as adjustment of medication, and evaluating caregiver strain and the need for referral to specialized care.7 To achieve this, Shulman et al.7 recommend the use of multiple sources (examination, questionnaires, and patient and caregiver reports) for gathering suitable information on disability in PD patients.
In previous studies, the MDS‐UPDRS Part II has demonstrated good psychometric properties and has shown its usefulness for assessing disability,19, 20 and it is recommended by the IPMDS.7 However, the accuracy of self‐reported data may be limited by many factors (memory, emotional state, environmental aspects), which may lead to discordance between different types of assessments and informants in PD disability.2, 25 This is particularly evident in the associations between MDS‐UPDRS Part II when answered with caregivers’ involvement and Barthel index and Schwab and England, two scales assessing dependence in which the caregivers’ point of view is relevant (Table 3). Patients tend to evaluate their ability better than it really is, whereas caregivers tend to evaluate patients’ ability in the contrary sense.26, 27 This tendency could be the explanation for the significant differences observed between correlations of the MDS‐UPDRS Part II with quality of life (PDQ‐8) and health state (EQ‐5D VAS) according to the respondent.
Nevertheless, in the present study, the MDS‐UPDRS Part II answered by the total sample reached high correlation and concordance coefficients with the rest of the disability rating scales, despite their differences in content, scoring, and structure. Previous studies support this result, reporting that patients’ self‐assessments of disability are reliable and accurate.25, 28
In general, the MDS‐UPDRS Part II obtained higher correlation coefficients with clinical and HRQoL measures than the other disability rating scales. In particular, disability, as measured by the MDS‐UPDRS Part II, was strongly associated to nonmotor features of PD (MDS‐UPDRS Part I and HADS‐D), with the clinician's global impression of severity (CISI‐PD), and with a disease‐specific HRQoL rating scale (PDQ‐8).19, 20 The MDS‐UPDRS Part II also reached high correlation coefficients with bradykinesia, axial manifestations, and motor fluctuations. The impact that some nonmotor symptoms (depression, fatigue, etc.) have on disability in PD,29, 30 and the negative effect that disability has on QoL of PD patients,2, 31 have been previously demonstrated. These findings highlight the need for implementing effective treatments for motor and nonmotor features to prevent the appearance of disability and dependence.
All disability ratings showed significant differences in scores between categories of patients grouped by sex, age, disease duration, HY, and MDS‐UPDRS Parts I, III, and IV cut‐offs (Table 3). In particular, women, older patients, and those with higher disease duration and more severe motor and nonmotor manifestations showed worse disability scores, as expected.30, 32, 33 Some studies have shown different severity levels in motor and nonmotor manifestations according to age at onset.34 However, in our study, there is a lack of significant differences in disability scores by age at onset, suggesting that those variations in severity do not translate into an impact on disability.
This study has several limitations. The sample was enrolled in specialized movement disorders units, not randomly selected, and the cross‐sectional design of the study does not allow for conclusions on causality and course of disability. In addition, we could not explore the comparative responsiveness of the scales in the study. However, the present study allowed the direct comparison of several disability assessments with different sources of information and structure, which is an infrequent scenario in PD.
In conclusion, assessment of disability in PD patients is adequately performed using a self‐assessed, specific tool such as the MDS‐UPDRS Part II. In the present study, this scale showed equivalence with or even better performance than some generic or specific rater‐based scales used for disability evaluation in PD.
Author Roles
1. Research project: A. Conception, B. Organization, C. Execution; 2. Statistical Analysis: A. Design, B. Execution, C. Review and Critique; 3. Manuscript: A. Writing of the first draft, B. Review and Critique.
C.R.‐B.: 1C, 2A, 2B, 3A
M.A.: 1C, 3B
T.A.: 1C, 3B
V.C.A.: 1C, 3B
P.C.: 1C, 3B
W.F.: 1C, 3B
N.G.: 1C, 3B
J.C.M.‐C.: 1C, 3B
M.R.‐V.: 1C, 3B
M.S.‐D.: 1C, 3B
D.B.: 1C, 3B
J.M.R.‐A.: 1C, 3B
K.R.C.: 1A, 1C, 3B
M.M.: 1A, 1B, 3B
P.M.‐M.: 1A, 1B, 2A, 2B, 2C, 3B
Disclosures
Ethical Compliance Statement: We confirm that we have read the Journal's position on issues involved in ethical publication and affirm that this work is consistent with those guidelines.
Funding Sources and Conflicts of Interest: This research did not receive any specific grant from funding agencies in the public, commercial, or not‐for‐profit sectors.
Financial Disclosures for the previous 12 months: V.C.A. received honoraria from UCB Pharma. N.G. received a grant from Boehringer Ingelheim (Program Tango and Parkinson's disease) and has participated in Advisory Boards for UCB and Allergan. J.C.M.‐C. received honoraria for speaking at meetings sponsored by AbbVie, UCB, Allergan, Merz, Italfarmaco, BIAL, and KRKA. M.R.‐V. received honoraria from Boehringer‐Ingelheim, Ever Neuro Pharma, UCB, Vanquish, Medtronic, and MedLearning. She participated in Advisory Boards for UCB Latin America and Teva. M.S.‐D. received an honorarium from Editorial Viguera as professor of a master course, and he received speaking honoraria from Abbot, Novartis, and Biopas. He received a grant from Boehringer Ingelheim and Biopas for a workshop. K.R.C. received honoraria from UCB, Abbvie, Britannia, US Worldmeds, Mundipharma, Medtronic, Napp, and Otsuka Pharmaceuticals in the last 3 years, and he acted as a consultant for UCB, Abbvie, Britannia, Medtronic, and Mundipharma. He received funding from Parkinson's UK, NIHR, European Commission, as well as educational grants from UCB, Britannia, Abbvie, and Medtronic. M.M. received royalties from Springer‐Verlag, Random House, Cambridge University Press, and Demos, and honoraria from Wiley/MDS. He participated in an Advisory Board for TEVA. He received grants from GSK, Allergan Honoraria: Lundbeck, and Boeheringer. He is Coeditor‐in‐Chief for Movement Disorders Clinical Practice. P.M.‐M. received an honorarium from the Editorial Viguera and Movement Disorder Society for lecturing in respective courses, and from AbbVie for participating on the Advisory Board for an epidemiological study. He received a grant from the International Parkinson and Movement Disorder Society for the Pilot Study of the MDS‐Non‐Motor Symptoms Scale. C.R.‐B., M.A., T.A., P.C., W.F., D.B., and J.M.R.‐A. report no sources of funding and no conflicts of interest.
Relevant disclosures and conflicts of interest are listed at the end of this article.
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