Redefining Treatment Success in Patients With Parkinson’s Disease
VALIDATED PD QUALITY-OF-LIFE MEASURES
Health-related quality of life is recognized as an important outcome measure in clinical studies of patients with chronic diseases.32 Parkinson’s disease is a complex, chronic illness that causes progressive disability and substantially impaired HRQOL.8,9,17 Motor, behavioral, and social function, in addition to the effects of treatment, are significant contributors to HRQOL in patients with PD. Measures that assess HRQOL provide a method of evaluating the overall efficacy of a specific treatment or the impact of the disease on the individual as a whole. These measures complement objective assessments by evaluating physical, emotional, and social functioning from the individual patient’s perspective.
Numerous assessment scales are available to evaluate HRQOL in patients with PD, including the PD Questionnaire (PDQ)-39 and PDQ-8, PD Quality of Life Scale, PD Quality of Life Questionnaire (PDQL), and Parkinson’s Impact Scale (PIMS).33-37 The Parkinson Quality of Life Questionnaire (PLQ) is also available to assess HRQOL in patients with PD but is validated only in German.32 Overall, the scales vary considerably in their focus on different quality-of-life measures and in the time required to conduct the assessment (Table 3). A systematic review evaluated the clinimetric properties of HRQOL instruments in clinical studies of PD published between 1965 and 2000.32 The authors identified 20 studies that assessed the characteristics of the PDQ-39, PDQL, PIMS, and PLQ and reported that all scales had acceptable internal consistency. The content validity was adequate for the PDQ-39, PDQL, and PLQ but was insufficient for the PIMS. The authors concluded that the selection of an HRQOL instrument depends on the factors to be assessed in the course of a clinical study. However, the PDQ-39 was highlighted as the most valuable HRQOL instrument overall because of its validity, satisfactory clinimetric characteristics, and availability in multiple languages. In contrast, the authors found the PIMS to be inadequate, as it consists of broad categories, does not assess cognitive functioning, and provides the least thorough evaluation of physical functioning.
Table 3. HRQOL Measures for Parkinson's disease
| Measure | Number of items in questionnaire | Description of items addressed |
|---|---|---|
| PDQ-3935 | 39 | Mobility, ADL, emotional well-being, stigma, social support, cognition, communication, physical discomfort |
| PDQ-836 | 8 | Mobility, ADL, emotional well-being, stigma, social support, cognition, communication, physical discomfort |
| PDQUALIF37 | 33 | Social function, self-image, sexuality, sleep patterns, outlook, physical function, independence, urinary function, plus 1 item of global HRQOL |
| PDQL34 | 37 | Parkinsonian symptoms, systemic symptoms, emotional function, social function |
| PIMS33a | 10 | Self-image, family relationships, community relationships, work, leisure, travel, safety, financial security, sexuality |
ADL, activities of daily living; HRQOL, health-related quality of life; PD, Parkinson’s disease; PDQ, Parkinson’s Disease Questionnaire; PDQL, Parkinson’s Disease Quality of Life Questionnaire; PDQUALIF, Parkinson’s Disease Quality of Life Scale; PIMS, Parkinson’s Impact Scale.
a Scale must be completed 3 times, 1 month apart.
A population-based study evaluated the relationship between HRQOL (as assessed by the PDQ-39) and clinical features of PD.17 Patients were rated with the Hoehn and Yahr scale and the motor section (part 3) of the UPDRS. Of 124 individuals identified as having probable PD, 97 study participants responded to the questionnaire, for an overall response rate of 78%. Patients with moderate-to-severe depression (based on Beck Depression Inventory scores), postural instability (as defined by the UPDRS), and a history of falls or gait difficulties had significantly worse PDQ-39 summary scores compared with patients without these features (P<0.001 for each comparison; Figure 3). The most substantial predictor of poor HRQOL was depression. This association between the presence of depression and poor HRQOL has been reported in other clinical studies evaluating HRQOL in patients with PD (up to 60% impairment in PDQ-39 scores).38,39
Figure 3. Clinical features of PD associated with significant reductions in HRQOL. HRQOL, health-related quality of life; PD, Parkinson’s disease; PDQ, PD Questionnaire.a Defined as Beck Depression Inventory Score <17.b Based on patient report upon interview. P<0.001 for comparisons of depression, history of falls, postural instability, and gait impairment.17
In summary, findings from multiple clinical studies demonstrate that psychological and social factors contribute substantially to an individual’s HRQOL.17,32,38,39 Depression is a common neuropsychiatric feature of PD, with an estimated prevalence of 11% to 44% and when present, is often associated with increased physical disability.8 Because nonmotor clinical features can be as disabling to patients with PD as the hallmark motor symptoms, focusing on only motor symptoms is imprudent. Effective management of motor and nonmotor symptoms through an individualized, patient-focused perspective is crucial to minimize disability, improve HRQOL, and ultimately achieve treatment success.
