Health status measurement in Parkinson's disease: validity of the PDQ-39 and Nottingham Health Profile

Is PDQ-39 a reliable measure of quality of life of patients at advanced stages of Parkinson's disease considered for Deep Brain Stimulation

Purpose

Parkinson's disease (PD) significantly impedes, especially at its advanced stages, the health-related quality of life (QoL) of patients. The Parkinson's disease questionnaire (PDQ-39) is a widely-used measure assessing the impact of the disease on the patients' QoL. To date, the reliability of PDQ-39 has not been selectively evaluated for patients at a particular delineated stage of the PD progression. Against this backdrop, the study aimed firstly to evaluate comprehensively the internal consistency reliability of PDQ-39 and the constituent scales specifically for patients at the advanced stages of PD who were candidates for Deep Brain Stimulation (DBS) surgery, and secondly, to compare the Cronbach's alpha coefficients with those reported in other studies conducted with patients across all stages of the PD progression.

Methods

The sample included 36 Bulgarian patients (29 men and 7 women) at advanced stages of PD (Hoehn and Yahr stage 4), PD duration, M = 11.06, SD = 3.50). The internal consistency reliability of the questionnaire and the constituent scales was assessed using three criteria: Cronbach's alpha coefficients, inter-item and item-total correlations.

Results

The internal consistency reliability indicators were satisfactory for the entire instrument and for most of the scales and similar to those reported in previous studies. None of the scales had low internal consistency reliability results across the three criteria. Except for the Communication scale, seven of the eight scales had Cronbach's alpha values that were satisfactory or marginally below the cut off score. All scales had acceptable inter-item correlations. Three of the scales (Emotional Well-Being, Cognition and Communication) contained more than one item with non-satisfactory item-total correlations. With minor exceptions, the removal of the items with low item-total correlations either did not improve or improved marginally or even decreased the Cronbach's alpha coefficients of the respective scale. The Communication scale was the only scale with a Cronbach's alpha coefficient that was both low and comparatively different to other studies and had as well low item-total correlations for all constituent items, thus showing non-satisfactory results on two of the three internal consistency reliability estimates. In contrast, the Mobility scale met all three internal consistency reliability criteria.

Conclusion

PDQ-39 is a reliable tool for assessing the QoL of patients at advanced stages of PD across multiple health-related domains. The questionnaire can be recommended for inclusion in the best practice guidelines for evaluating DBS candidacy and the efficacy of DBS treatment for patients' QoL.

Psychometric properties of the Parkinson's disease Questionnaire-39 and its short form Parkinson's disease Questionnaire-8: A systematic review and meta-analysis

Parkinson's disease (PD) affects Quality of Life (QoL), since it is responsible for cognitive impairment, non-motor, and motor symptoms. Outcome measures are fundamental for evaluating treatment's effect on QoL over time. This systematic review aimed to identify the psychometric properties of PDQ-39 and PDQ-8 in the different populations in which they were validated. The electronic databases systematically searched are MEDLINE (via PubMed), CINAHL, SCOPUS, and Web of Science; the research was conducted in July 2023. The psychometric properties considered were those of the COnsensus-based Standards for the selection of health Measurement Instruments (COSMIN) checklist. Risk of bias was assessed using the COSMIN checklist. The search identified 1306 articles. 398 duplicates were eliminated; 908 articles were analyzed reading title and abstract; 799 were finally excluded because used PDQ-39 and PDQ-8 as outcome measures or were not dealing with psychometric properties; 66 articles were excluded after reading the full text. 43 articles were included in the review; meta-analysis showed all the Cronbach's alpha values were statistically significant for all the subscales of PDQ-39 and PDQ-8. PDQ-39 demonstrated to be a specific HRQoL questionnaire that is correlated with generic HRQoL questionnaires, in fact in many studies included in the review, correlations with SF-36 were found. In the last studies about psychometric properties of PDQ-8 emerged that it is a practical and informative instrument that can be easily used in clinical settings, especially in busy ones, but also in large-scale studies in which a brief instrument would be preferred.

Exercise-Induced Functional Changes in People with Parkinson's Disease following External Cueing and Task-Based Intervention

Introduction

The purpose of this study was to evaluate change in motor function, gait speed, dynamic balance, balance confidence, and quality of life (QoL) in nine participants with Parkinson's disease (PwPD) completing Lee Silverman Voice Treatment BIG (LSVT-BIG), an external cueing and task-based intervention. Although supported as an efficacious treatment in PwPD, there is limited research examining clinically meaningful change in outcome measures related to external cueing and task-based interventions.

Materials and Methods

This was a case series of nine PwPD (age range 64-76 years, 55% male) who completed the LSVT-BIG protocol. Disease duration ranged from 1 to 17 years and was classified as moderate in all participants (Hoehn and Yahr = 2 or 3). Outcome measures included motor function (MDS-UPDRS Part III Motor), gait speed, dynamic balance (MiniBEST), Activities-specific Balance Confidence (ABC), and Summary Index for PD Quality of Life 39 (PDQ-SI). Assessments were completed at baseline (BASE), end of treatment (EOT), and 4 weeks after EOT (EOT+4).

Results

Minimal detectable change (MDC) or minimal clinical important difference (MCID) was observed in one or more outcome measures in 8 of 9 participants at EOT and EOT+4 across domains of motor function (67%, 78%), gait speed (78%, 67%), balance confidence (44%, 33%), quality of life (44%, 78%), and dynamic balance (22%, 22%). Discussion. In this case series, 8 of 9 participants showed MDC or MCID changes across multiple functional domains. Improvements were observed immediately post (EOT) and 4-week post-treatment (EOT+4) suggesting a temporal component of the LSVT-BIG impact on functional change. Future research should include clinical trials to examine additional external cueing and task-based intervention efficacy with consideration of intensity, frequency, and mode of delivery across disease severity.

Validation of the Swedish Patient-Reported Outcomes in Parkinson's Disease Scale in Outpatients

BACKGROUND

Successful treatment of Parkinson's disease (PD) requires symptom monitoring. Patient-Reported Outcomes in Parkinson's Disease (PRO-PD) is a broad scale that covers 35 motor and nonmotor symptoms, but its validation is limited.

OBJECTIVE

The aim was to validate PRO-PD in a random sample of outpatients with PD.

METHODS

Of 2123 PD patients who visited outpatient clinics in West Sweden over a 12-month period, 25% were randomly selected and invited to participate in a longitudinal observational study. Included patients were assessed at baseline, 1 year, and 3 years, with a subset also assessed at 3 to 6 months. The assessments included PRO-PD, other patient-reported scales, and Clinical Impression of Severity Index for Parkinson's Disease (CISI-PD).

RESULTS

The study included 286 PD patients. PRO-PD ratings were available from 716 (96%) of 747 study visits. All PRO-PD items exhibited positive skewness without ceiling effects. Internal consistency at baseline was excellent (Cronbach's α: 0.93). Six-month test-retest reliability was good (intraclass correlation coefficient: 0.87). Convergent validity was good, with correlation coefficients between total PRO-PD and the 8-Item Parkinson's Disease Questionnaire of 0.70, the Non-Motor Symptoms Questionnaire of 0.70, EuroQoL Five-Dimension Five-Level Scale of 0.71, and CISI-PD of 0.69. Median PRO-PD score at baseline was 995 (interquartile range: 613-1399), with a median yearly increase of 71 (interquartile range: -21 to 111). Items representing axial motor symptoms increased most over time. The minimal clinically important change in total score was 119.

CONCLUSIONS

PRO-PD was found reliable and valid for monitoring symptoms in a representative sample of outpatients with PD. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Using network analysis to explore the validity and influential items of the Parkinson's Disease Questionnaire-39

Quality of life (QoL) in people with Parkinson´s disease (PD) is commonly measured with the PD questionnaire-39 (PDQ-39), but its factor structure and construct validity have been questioned. To develop effective interventions to improve QoL, it is crucial to understand the connection between different PDQ-39 items and to assess the validity of PDQ-39 subscales. With a new approach based on network analysis using the extended Bayesian Information Criterion Graphical Least Absolute Shrinkage and Selection Operator (EBICglasso) followed by factor analysis, we mostly replicated the original PDQ-39 subscales in two samples of PD patients (total N = 977). However, model fit was better when the "ignored" item was categorized into the social support instead of the communication subscale. In both study cohorts, "depressive mood", "feeling isolated", "feeling embarrassed", and "having trouble getting around in public/needing company when going out" were identified as highly connected variables. This network approach can help to illustrate the relationship between different symptoms and direct interventional approaches in a more effective manner.

Neurological Health: Not Merely the Absence of Disease: Current Wellbeing Instruments Across the Spectrum of Neurology

OBJECTIVE

Well-being and quality of life can vary independently of disease. Instruments measuring well-being and quality of life are commonly used in neurology, but there has been little investigation into the extent in which they accurately measure wellbeing/quality of life or if they merely reflect a diseased state of an individual.

DESIGN

Systematic searches, thematic analysis and narrative synthesis were undertaken. Individual items from instruments represented in ≥ 5 publications were categorised independently, without prior training, by five neurologists and one well-being researcher, as relating to 'disease-effect' or 'Well-being' with a study-created instrument. Items were additionally categorised into well-being domains.

DATA SOURCES

MEDLINE, EMBASE, EMCARE and PsycINFO from 1990 to 2020 were performed, across the 13 most prevalent neurological diseases.

RESULTS

301 unique instruments were identified. Multiple sclerosis had most unique instruments at 92. SF-36 was used most, in 66 studies. 22 instruments appeared in ≥ 5 publications: 19/22 'well-being' outcome instruments predominantly measured disease effect (Fleiss kappa = .60). Only 1/22 instruments was categorised unanimously as relating to well-being. Instruments predominantly measured mental, physical and activity domains, over social or spiritual.

CONCLUSIONS

Most neurological well-being or quality-of-life instruments predominantly measure disease effect, rather than disease-independent well-being. Instruments differed widely in well-being domains examined.

Outcome Measures for Disease-Modifying Trials in Parkinson's Disease: Consensus Paper by the EJS ACT-PD Multi-Arm Multi-Stage Trial Initiative

BACKGROUND

Multi-arm, multi-stage (MAMS) platform trials can accelerate the identification of disease-modifying treatments for Parkinson's disease (PD) but there is no current consensus on the optimal outcome measures (OM) for this approach.

OBJECTIVE

To provide an up-to-date inventory of OM for disease-modifying PD trials, and a framework for future selection of OM for such trials.

METHODS

As part of the Edmond J Safra Accelerating Clinical Trials in Parkinson Disease (EJS ACT-PD) initiative, an expert group with Patient and Public Involvement and Engagement (PPIE) representatives' input reviewed and evaluated available evidence on OM for potential use in trials to delay progression of PD. Each OM was ranked based on aspects such as validity, sensitivity to change, participant burden and practicality for a multi-site trial. Review of evidence and expert opinion led to the present inventory.

RESULTS

An extensive inventory of OM was created, divided into: general, motor and non-motor scales, diaries and fluctuation questionnaires, cognitive, disability and health-related quality of life, capability, quantitative motor, wearable and digital, combined, resource use, imaging and wet biomarkers, and milestone-based. A framework for evaluation of OM is presented to update the inventory in the future. PPIE input highlighted the need for OM which reflect their experience of disease progression and are applicable to diverse populations and disease stages.

CONCLUSION

We present a range of OM, classified according to a transparent framework, to aid selection of OM for disease-modifying PD trials, whilst allowing for inclusion or re-classification of relevant OM as new evidence emerges.

Using gait robotics to improve symptoms of Parkinson's disease: an open-label, pilot randomized controlled trial

BACKGROUND

People with Parkinson's Disease (PD) have difficulty participating in exercise.

AIM

The primary objective of this pilot randomized controlled trial (RCT) was to determine if 8 weeks (2x per week) of bilateral exoskeleton (Exo) exercise results in positive changes in cognition and participation in adults with PD compared to exercising without an exoskeleton (Nxo) or wait-list control (Con).

DESIGN

Open-label, parallel, pilot randomized controlled trial.

SETTING

Neurorehabilitation clinic in a large urban center.

POPULATION

Adults 50-85 years old with a confirmed diagnosis of PD.

METHODS

Eight weeks of twice-weekly combined aerobic, strength and mobility exercise or wait-list control. Participants were randomly assigned to exercise with no exoskeleton (Nxo), exercise with the exoskeleton (Exo), or waitlist control (Con). Primary endpoints were change in cognitive function (SCOPA-COG) and mood. Secondary endpoints were change in gait speed, six-minute walk test (6MWT), freezing of gait, balance, and PD-specific health and quality of life outcomes. Safety endpoint was analysis of adverse events (AE).

RESULTS

Forty participated in the trial (Exo, N.=13; Nxo, N.=14; Con, N.=13). Significant improvement in the Memory & Learning domain of the SCOPA-COG (P=0.014) and 6MWT (P=0.008) were detected for the Exo group compared to the Nxo and/or Con group. No other statistically significant between-groups effects were found. There were no serious or unanticipated AE.

CONCLUSIONS

Functional exercise with a low-profile overground exoskeleton showed promising results for improving memory and gait endurance in people with PD across HY stages I-IV.

CLINICAL REHABILITATION IMPACT

Exoskeletons can improve participation in high-intensity exercise.

Correlation between depression and quality of life in patients with Parkinson's disease

OBJECTIVE

To understand the distribution of Parkinson's disease questionnaire-39 (PDQ-39) scores in Parkinson's disease (PD) patients with or without depression, and to analyze the factors that influence the quality of life of PD patients.

MATERIALS AND METHODS

300 PD patients were enrolled. Patients' general information and the results of assessments including UPDRS, H-Y, HAMD, HAMA, ADL and PDQ-39 were collected. They were divided into depression group and non-depression group according to HAMD score. The relationship between PD-related depression and quality of life and the factors that influence the quality of life of PD patients were analyzed based on PDQ-39 score.

RESULTS

111 patients with depression (37.0 %) and 189 patients without depression (63.0 %) were enrolled. The scores of PDQ-39 summary index (PDQ-39 SI) in the depression group were significantly higher than those in the non-depression group in all domains (P < 0.05). Patients in the depression group had a longer disease duration (6.89 ± 4.70 vs. 5.52 ± 4.12, P < 0.038), a higher UPDRS-III score (30.1 ± 13.55 vs. 25.2 ± 11.73, P < 0.001), and a higher H-Y stage level (2.41 ± 0.853 vs. 2.13 ± 0.707, P < 0.001), compared with patients in the non-depression group. All factors including age, disease duration, UPDRS-III, H-Y stage, HAMD score and HAMA score, may independently affected PDQ-39SI in PD patients, among which HAMD had the greatest effect. HAMD and HAMA were correlated with PDQ-39 in its all eight domains.

CONCLUSION

PD patients with psychological problems such as anxiety and depression may lead to a significant decline in the quality of life of patients in all domains.

Tools to assess the quality of life in patients with Parkinson's disease: a systematic review

INTRODUCTION

The clinical, social, and economic implications of Parkinson's disease (PD) are significant; disability occurs leading to a low quality of life (QoL). Information on the QoL of patients with PD and studies on the relationship between QoL and motor and cognitive function are necessary for both research and clinical use to make informed decisions in healthcare and rehabilitation. The aim of this study was to determine which scales are most used to assess QoL in patients with PD.

AREA COVERED

A literature search was conducted in MEDLINE, Scopus, CINAHL, PsycINFO, and Web of Science. Two authors independently identified eligible studies based on predefined inclusion criteria and extracted the data. Study quality and the risk of bias were assessed using the COSMIN checklist.

EXPERT OPINION

116 suitable studies were included, and 42 different instruments were identified. The most frequently used scales were the 39-items and 8-items Parkinson's Disease Questionnaire (PDQ-39) (PDQ-8). These findings suggest further investigation of existing PD outcome measures would benefit patients, researchers, and clinicians. Validated, universal outcome measures are required to allow comparisons across practice; therefore, we recommend that future researchers use a common set of outcome assessments based on the results of this review.

Evaluation of upper limb function with digitizing tablet-based tests: reliability and discriminative validity in healthy persons and patients with neurological disorders

PURPOSE

To evaluate discriminative validity, relative reliability and absolute reliability of four tablet-based tests for the evaluation of upper limb motor function in healthy persons and patients with neurological disorders.

METHODS

Cross-sectional study in 54 participants: 29 patients with upper limb movement impairment due to a neurological condition recruited from an inpatient rehabilitation centre and 25 healthy persons. Accuracy, speed and path length were analysed for four tablet-based tests: "Spiral drawings," "Tapping," "Follow the dot" and "Trace a star." The area under the receiver operating characteristic curve (AUC) was used to evaluate discriminative validity. Relative reliability was analysed with the intra-class correlation coefficient (ICC), and absolute reliability by limits of agreement (LoA) and minimal detectable difference (MDD).

RESULTS

All four tests showed excellent discriminative validity for the parameter accuracy (AUC 0.93-0.98). Tapping was the best test for discriminating patients from healthy persons. Test-retest reliability was good for accuracy in all tests (ICC = 0.76-0.88), but poor to moderate for speed and path length (ICC = 0.20-0.69). The MDD varied between 14% and 38%. Performance on the four tablet-based tests was stable between sessions, indicating that there was no learning effect.

CONCLUSION

The parameter accuracy showed excellent discriminative validity and reliability in all four tablet-based tests. Discriminative validity was excellent for all three parameters in the Tapping test. In the other tasks speed showed good to poor reliability, while the reliability of path-length was poor in all tasks. Results were comparable for the dominant and non-dominant hand. Tablet-based tests have the advantage that patients can use them for self-monitoring of upper limb motor function.Implications for rehabilitationFour tablet-based tests for the assessment of upper limb motor function in patients with upper limb neurological dysfunction were evaluated: "Spiral drawings", "Tapping", "Follow the dot" and "Trace a star". The parameter accuracy in these four tests had excellent discriminative validity and good reliability.Patients can perform the tests independently at home for self-monitoring of progress. This may increase patients' motivation to exercise at home.The results can be sent to physicians, enabling the earlier detection of deterioration, which may require medical attention.

Clinical Progression of Parkinson's Disease: Insights from the NINDS Common Data Elements

BACKGROUND/OBJECTIVE

To synchronize data collection, the National Institute of Neurological Disorders and Stroke (NINDS) recommended Common Data Elements (CDEs) for use in Parkinson's disease (PD) research. This study delineated the progression patterns of these CDEs in a cohort of PD patients.

METHODS

One hundred-twenty-five PD patients participated in the PD Biomarker Program (PDBP) at Penn State. CDEs, including MDS-Unified PD Rating Scale (UPDRS)-total, questionnaire-based non-motor (-I) and motor (-II), and rater-based motor (-III) subscales; Montreal Cognitive Assessment (MoCA); Hamilton Depression Rating Scale (HDRS); University of Pennsylvania Smell Identification Test (UPSIT); and PD Questionnaire (PDQ-39) were obtained at baseline and three annual follow-ups. Annual change was delineated for PD or subgroups [early = PDE, disease duration (DD) <1 y; middle = PDM, DD = 1-5 y; and late = PDL, DD > 5 y] using mixed effects model analyses.

RESULTS

UPDRS-total, -II, and PDQ-39 scores increased significantly, and UPSIT decreased, whereas UPDRS-I, -III, MoCA, and HDRS did not change, over 36 months in the overall PD cohort. In the PDE subgroup, UPDRS-II increased and UPSIT decreased significantly, whereas MoCA and UPSIT decreased significantly in the PDM subgroup. In the PDL subgroup, UPDRS-II and PDQ-39 increased significantly. Other metrics within each individual subgroup did not change. Sensitivity analyses using subjects with complete data confirmed these findings.

CONCLUSION

Among CDEs, UPDRS-total, -II, PDQ-39, and UPSIT all are sensitive metrics to track PD progression. Subgroup analyses revealed that these CDEs have distinct stage-dependent sensitivities, with UPSIT for DD < 5 y, PDQ-39 for DD > 5 y, UPDRS-II for early (DD < 1) or later stages (DD > 5).

Satisfaction with Care in Late Stage Parkinson's Disease

In late stage Parkinson's disease (PD) (i.e., Hoehn and Yahr (HY) stages IV-V), both motor and nonmotor symptoms (NMS) are pronounced, and the patients become increasingly dependent on help in their daily life. Consequently, there is an increasing demand on health-care and social care resources for these patients and support for their informal caregivers. The aim of this study was to assess satisfaction with care in late stage PD patients and to identify factors associated with satisfaction with care. Moreover, to assess their informal caregivers' satisfaction with support and to identify factors associated with caregivers' satisfaction with support. Factors potentially associated with satisfaction with care/support were assessed in 107 late stage PD patients and their informal caregivers (n=76) and entered into multivariable logistic regression analyses. Fifty-eight (59%) of the patients and 45 (59%) of the informal caregivers reported satisfaction with their overall care/support. Patients satisfied with their care reported higher independence in activities of daily living (ADL) (Katz ADL index; P=0.044), less depressive symptoms (Geriatric Depression Scale, GDS-30; P=0.005), and higher individual quality of life (QoL) (Schedule for the Evaluation of Individual Quality of Life Questionnaire, SEIQoL-Q; P=0.036). Multivariable logistic regression analyses identified depressive symptoms (P=0.015) and independence in ADL (P=0.025) as independently associated with satisfaction with care. For informal caregivers, the analyses identified patients' HY stage (P=0.005) and caregivers' QoL (Alzheimer's Carers Quality of Life Inventory, ACQLI; P=0.012) as independently associated with satisfaction with caregiver support. The results indicate that an effective both pharmacological and nonpharmacological PD therapy is important, to adequately treat motor and NMS (e.g., depressive symptoms) in order to improve depressive symptoms and patient independence in ADL. This may benefit not only the patients, but also their informal caregivers.

Validation of a Questionnaire to Delineate the Clinical Trial Nursing Roles in Korea

BACKGROUND

In clinical trials, research nurses play a particularly important role in promoting cancer care best practices. However, no Korean questionnaire has been developed to define the clinical trial nursing roles based on Good Clinical Practice standards.

OBJECTIVE

The aim of this study was to cross-culturally evaluate the reliability and validity of a Korean version of the Clinical Trials Nursing Questionnaire (CTNQ) among Korean clinical research nurses.

METHODS

Cross-cultural adaptation was performed, with forward and backward translation, a pilot test (linguistic validation), and a field test. Validation was performed by questioning 53 clinical research nurses who were working in clinical cancer centers at 5 tertiary university hospitals. The distribution of the item responses and internal consistency reliability were assessed using the ceiling and floor effects, Cronbach's α, and the item-total correlation. Construct validity was assessed using Spearman correlation analysis and principal-component factor analysis.

RESULTS

The distributions of the item responses and the item-total correlation were generally appropriate. The Cronbach's α values for the frequency scale and the importance scale were 0.852 and 0.899, respectively. Eight sections of the Korean CTNQ were generally correlated with each other. The frequency subscale loaded on 1 factor, and the importance subscale loaded on 2 factors, with broadly similar factor loadings.

CONCLUSION

The Korean version of the CTNQ is reliable, valid, and interchangeable with the original CTNQ.

IMPLICATIONS FOR PRACTICE

The Korean version of the CTNQ can be used to validly and reliably assess the clinical trial nursing roles in Korea.

Measuring Anxiety in Patients With Early-Stage Parkinson's Disease: Rasch Analysis of the State-Trait Anxiety Inventory

The State-Trait Anxiety Inventory (STAI), composed of two 20-item subscales (STAI-state and STAI-trait), has been increasingly used to assess anxiety symptoms in patients with Parkinson's disease (PD). However, the clinimetric attributes of the STAI under the statistical framework of the item-response theory (IRT) have not been fully elucidated within this population to date. We performed an IRT-based Rasch analysis of the STAI outcomes of patients with de novo PD from the Parkinson's Progression Markers Initiative database. The unidimensionality, Rasch model fit, scale targeting, separation reliability, differential item functioning, and response category utility of the STAI were statistically evaluated. A total of 326 (209 males, 117 females) patients without cognitive dysfunction were enrolled in our study. The original versions of the STAI-state and STAI-trait had acceptable separation reliability but lacked appropriate response category functioning, exhibited scale off-targeting, and several items demonstrated poor fit to the Rasch model. The response categories were reduced from four to three, and the rescored three-point TASI-trait demonstrated a marked improvement in clinimetric properties without a significant impact on unidimensionality and separation reliability. The rescored three-point version of the STAI-state required the additional removal of four misfitting items in order to improve the Rasch model fit. To our knowledge, this is the first study to assess the measurement properties based on the IRT of the STAI in patients with PD. Our Rasch analysis identified the components requiring possible amendments in order to improve the clinimetric attributes of the STAI.

A randomized, controlled pilot study of the effects of vitamin D supplementation on balance in Parkinson's disease: Does age matter?

Objectives

To explore if short term, high dose vitamin D supplementation is safe and improves balance in persons with Parkinson's disease (PD).

Methods

A pilot randomized, double-blind intervention trial to measure the effects of 16 weeks of high dose vitamin D (10,000 IU/day) on balance as well as other motor and non-motor features of PD. We measured balance, gait, strength, falls, cognition, mood, PD severity, and quality of life before and after 16 weeks of high dose vitamin D supplementation or placebo. All participants also received 1000 mg calcium once daily.

Results

Fifty-one randomized participants completed sixteen weeks of high dose vitamin D supplementation or placebo. The intervention resulted in a rise in serum concentrations of vitamin D (25-OH) (30.2 ng/ml to 61.1 ng/ml) and was well tolerated with no serious adverse events. Serum vitamin D (25-OH) levels rose steadily and did not suggest a leveling off at the end of the 16 weeks. There was not an improvement in the primary endpoint, balance as measured by the Sensory Organization Test (p = 0.43). A post hoc analysis examining treatment effects in younger (ages 52–66) versus older (ages 67–86) participants found a significant improvement in the SOT of 10.6 points in the younger half of the cohort (p = 0.012).

Conclusions

Short term, high dose vitamin D supplementation appears safe in persons with PD, but did not significantly improve balance as measured with the Sensory Organization Test in this pilot study population. A post hoc analysis suggests that vitamin D may have potential for improving balance in a younger population with PD. High dose vitamin D supplementation in PD needs further study especially in light of new research suggesting that mega doses and even moderate doses (as low as 4000IU a day) may increase falls in an older populations.

Trial registration

ClinicalTrials.gov: NCT01119131.

Analyzing differential item functioning of the Nottingham Health Profile by Mixed Rasch Model

Objectives

This study aims to evaluate whether items in the Turkish version of the Nottingham Health Profile (NHP) function differently according to age, sex, and duration of pain using the Mixed Rasch Model (MRM).

Patients and methods

The NHP data of patients with low back pain from a previous study was analyzed. To analyze differential item functioning (DIF) within the items of the NHP, the MRM was used. Age, sex, and duration of pain were considered factors which could cause DIF. The most powerful factor to define latent classes derived from the MRM was estimated using the Rasch tree method.

Results

The two-class mixture version of the nominal response model was identified as the best fitting model for the physical mobility, sleep, and social isolation sections. For the physical mobility dimension, some items showed DIF by age and for the social isolation dimension some items showed DIF by sex. For the sleep dimension, latent classes were unable to be explained by age, sex, and duration of pain. Items in other dimensions of the NHP were DIF-free and no items showed DIF according to age, sex, and duration of pain.

Conclusion

The results of this study may shed light on explaining the different response behavior of patients on the items of the NHP. Age and sex were found to be variables affecting item responses of NHP. Contrary to expectations, duration of pain did not cause DIF for any item. From the perspective of DIF, it can be concluded that NHP scale is a robust scale in terms of validity.

Evaluation of PDQ-8 and its relationship with PDQ-39 in China: a three-year longitudinal study

Background

Parkinson’s disease is characterized by motor and non-motor symptoms with wide ranging impacts on the health-related quality of life. The 39-item Parkinson’s disease Questionnaire (PDQ-39) is the most widely used PD-specific health-related quality-of-life questionnaire. The short-form 8-item Parkinson’s disease Questionnaire (PDQ-8) was found to produce results similar to that of the PDQ-39 cross-culturally. However, there is no evaluation of the PDQ-8 in the mainland of China.

Methods

In this longitudinal study, 283 patients with Parkinson’s disease were recruited. The PDQ-39, the PDQ-8 and other scales were administered. Patients attended the clinic once annually for three years to complete the scales.

Results

The PDQ-8 was found to have good validity and reliability. There was a strong correlation between the summary indices of the PDQ-8 and the PDQ-39 (r=0.93, P<0.001). Results suggested that the PDQ-8 was also associated with other clinical scales of mobility, depression and cognition. The convergent validity and discriminant validity of the PDQ-8 were demonstrated by item-to-dimension correlations. There was acceptable internal consistency of the PDQ-8 (Cronbach’s α: 0.80; Item-scale correlation efficient: 0.56–0.72). The PDQ-8 replicated the results of the PDQ-39 well at all follow-up time points (intraclass correlation coefficient: 0.96–0.98). In addition, there was good test-retest reliability of the PDQ-8.

Conclusion

The PDQ-8 is a valid and reliable instrument assessing health-related quality of life for PD patients in the mainland of China.

Electronic supplementary material

The online version of this article (doi:10.1186/s12955-017-0742-5) contains supplementary material, which is available to authorized users.

Factors associated with life satisfaction in Parkinson's disease

OBJECTIVES

To identify factors associated with life satisfaction (LS) in people with Parkinson's disease (PD), including a specific focus on those with late-stage PD.

MATERIAL AND METHODS

The study included 251 persons with PD (median age 70 years; PD duration 8 years). Analyses involved the total sample and a subsample with late-stage PD, that is Hoehn and Yahr stages IV and V (n=62). LS was assessed with item 1 of the Life Satisfaction Questionnaire (LiSat-11). Simple logistic regression analyses were performed for both the total sample and for the subsample with late-stage PD. For the total sample, a multivariable logistic regression analysis was also performed.

RESULTS

In the total sample, 12 of the 20 independent variables were significantly associated with LS: need of help with ADL; walking difficulties; number of non-motor symptoms (NMS); fatigue; depressive symptoms; general self-efficacy; motor symptoms; pain; PD severity; freezing episodes; gender (woman); and fluctuations. When controlling for age and gender in the multivariable logistic regression model, depressive symptoms were negatively associated with high LS and general self-efficacy was positively associated with high LS. In late-stage PD, simple logistic regression analyses (controlling for age and gender) identified the following factors as associated with LS: number of NMS, general self-efficacy, walking difficulties and fatigue.

CONCLUSIONS

This study provides new knowledge on factors associated with LS in a PD sample, including those with late-stage PD. As the ultimate goal for PD care should be improvement in LS, the results have direct clinical implication.

Potential of APDM mobility lab for the monitoring of the progression of Parkinson's disease

APDM's Mobility Lab system provides portable, validated, reliable, objective measures of balance and gait that are sensitive to Parkinson's disease (PD). In this review, we describe the potential of objective measures collected with the Mobility Lab system for tracking longitudinal progression of PD. Balance and gait are among the most important motor impairments influencing quality of life for people with PD. Mobility Lab uses body-worn, Opal sensors on the legs, trunk and arms during prescribed tasks, such as the instrumented Get Up and Go test or quiet stance, to quickly quantify the quality of balance and gait in the clinical environment. The same Opal sensors can be sent home with patients to continuously monitor the quality of their daily activities. Objective measures have the potential to monitor progression of mobility impairments in PD throughout its course to improve patient care and accelerate clinical trials.

The Rationale for Exercise in the Management of Pain in Parkinson's Disease

Pain is a distressing non-motor symptom experienced by up to 85% of people with Parkinson’s disease (PD), yet it is often untreated. This pain is likely to be influenced by many factors, including the disease process, PD impairments as well as co-existing musculoskeletal and/or neuropathic pain conditions. Expert opinion recommends that exercise is included as one component of pain management programs; however, the effect of exercise on pain in this population is unclear. This review presents evidence describing the potential influence of exercise on the pain-related pathophysiological processes present in PD. Emerging evidence from both animal and human studies suggests that exercise might contribute to neuroplasticity and neuro-restoration by increasing brain neurotrophic factors, synaptic strength and angiogenesis, as well as stimulating neurogenesis and improving metabolism and the immune response. These changes may be beneficial in improving the central processing of pain. There is also evidence that exercise can activate both the dopaminergic and non-dopaminergic pain inhibitory pathways, suggesting that exercise may help to modulate the experience of pain in PD. Whilst clinical data on the effects of exercise for pain relief in people with PD are scarce, and are urgently needed, preliminary guidelines are presented for exercise prescription for the management of central neuropathic, peripheral neuropathic and musculoskeletal pain in PD.

Is excessive daytime sleepiness a separate manifestation in Parkinson's disease?

BACKGROUND

Excessive daytime sleepiness (EDS) is common in Parkinson's disease (PD), but its role and relation to other PD features is less well understood.

OBJECTIVE

To investigate potential predictors of EDS in PD and to explore how EDS relates to other motor and non-motor PD features.

METHODS

118 consecutive persons with PD (54% men; mean age, 64) were assessed regarding EDS using the Epworth Sleepiness Scale (ESS) and a range of motor and non-motor symptoms. Variables significantly associated with ESS scores in bivariate analyses were used in multiple regression analyses with ESS scores as the dependent variable. Principal component analysis (PCA) was conducted to explore the interrelationships between ESS scores and other motor and non-motor PD aspects.

RESULTS

Among 114 persons with complete ESS data, significant independent associations were found between ESS scores and axial/postural/gait impairment, depressive symptoms, and pain (R2, 0.199). ESS scores did not load significantly together with any other PD features in the PCA.

CONCLUSIONS

Only a limited proportion of the variation in EDS could be accounted for by other symptoms, and EDS did not cluster together with any other PD features in PCAs. This suggests that EDS is a separate manifestation differing from, for example, poor sleep quality and fatigue.

Nonmotor symptoms in a malaysian Parkinson's disease population

Background. The nonmotor symptoms are important determinants of health and quality of life in Parkinson's disease but are not well recognized and addressed in clinical practice. This study was conducted to determine the prevalence of nonmotor symptoms and their impact on quality of life in patients with Parkinson's disease. Methods. This was a cross-sectional study among patients with idiopathic Parkinson's disease. Exclusion criteria were a Mini Mental State Examination score of <21/30. Prevalence of nonmotor symptoms was determined using the NMSQuest. The severity of nonmotor symptoms and the quality of life were assessed using validated disease-specific questionnaires (PDQ-39 and NMSS). Results. A total of 113 patients consisting of 60 males and 53 females were recruited. The median duration of illness was 5.0 (2.0-8.0) years. The prevalence rate of nonmotor symptoms in our cohort was 97.3%. The most common reported nonmotor symptom in our cohort was gastrointestinal (76.1%). We found that the severity of the nonmotor symptoms was associated with poorer quality of life scores (r s : 0.727, P < 0.001). Conclusions. Nonmotor symptoms were highly prevalent in our patients with Parkinson's disease and adversely affected the quality of life of our patients. In contrast to western studies, the most common nonmotor symptom is gastrointestinal. The possibility of an Asian diet playing a role in this observation requires further study.

The Significance of Importance: An Evaluation of Ferrans and Powers’ Quality of Life Index

Ferrans and Powers' Quality of Life Index (QLI) defines and assesses quality of life (QoL) in terms of importance-weighted life satisfaction. This study assessed the value of such weights and explored the relationship between weighted and unweighted (satisfaction only) scores and single-item rated overall life satisfaction (LS) and QoL. Data were collected by a postal survey to 81 Parkinson's disease patients (88% response rate). Correlations between weighted and unweighted QLI scores were >or=0.96, except for one subscale (r ( s ) = 0.85). Item non-response rates ranged between 4.2 and 45.1% and 1.4 and 38% for the weighted and unweighted QLI, respectively. Cronbach's alpha exceeded 0.7 for weighted and unweighted versions of two out of the four subscales and the total score. Scaling success rates were similar for weighted and unweighted scores and did not support the current subscale structure. Unexpectedly, weighted total scores correlated stronger with LS than with QoL, and unweighted scores displayed the opposite pattern. This study found no advantages by using importance-weighted satisfaction scores. The correlational pattern with overall LS and QoL challenges the QLI approach to QoL, although these observations may relate to the use of multiplicative item weights. This study has implications also beyond the QLI regarding, e.g., the use of multiplicative weights and the relationship between life satisfaction and QoL.

Automatic and objective assessment of alternating tapping performance in Parkinson's disease

This paper presents the development and evaluation of a method for enabling quantitative and automatic scoring of alternating tapping performance of patients with Parkinson's disease (PD). Ten healthy elderly subjects and 95 patients in different clinical stages of PD have utilized a touch-pad handheld computer to perform alternate tapping tests in their home environments. First, a neurologist used a web-based system to visually assess impairments in four tapping dimensions ('speed', 'accuracy', 'fatigue' and 'arrhythmia') and a global tapping severity (GTS). Second, tapping signals were processed with time series analysis and statistical methods to derive 24 quantitative parameters. Third, principal component analysis was used to reduce the dimensions of these parameters and to obtain scores for the four dimensions. Finally, a logistic regression classifier was trained using a 10-fold stratified cross-validation to map the reduced parameters to the corresponding visually assessed GTS scores. Results showed that the computed scores correlated well to visually assessed scores and were significantly different across Unified Parkinson's Disease Rating Scale scores of upper limb motor performance. In addition, they had good internal consistency, had good ability to discriminate between healthy elderly and patients in different disease stages, had good sensitivity to treatment interventions and could reflect the natural disease progression over time. In conclusion, the automatic method can be useful to objectively assess the tapping performance of PD patients and can be included in telemedicine tools for remote monitoring of tapping.

[Advanced Parkinson's disease: clinical characteristics and treatment (part 1)]

INTRODUCTION

A large percentage of patients with Parkinson's disease (PD) develop motor fluctuations, dyskinesias, and severe non-motor symptoms within 3 to 5 years of starting dopaminergic therapy, and these motor complications are refractory to treatment. Several authors refer to this stage of the disease as advanced Parkinson's disease.

OBJECTIVE

To define the clinical manifestations of advanced PD and the risk factors for reaching this stage of the disease.

DEVELOPMENT

This consensus document has been prepared by using an exhaustive literature search and by discussion of the contents by an expert group on movement disorders of the Sociedad Española de Neurología (Spanish Neurology Society), coordinated by two of the authors (JK and MRL).

CONCLUSIONS

Severe motor fluctuations and dyskinesias, axial motor symptoms resistant to levodopa, and cognitive decline are the main signs in the clinical phenotype of advanced PD.

An introduction to Rasch analysis for Psychiatric practice and research

This article aims to present the main characteristics of Rasch analysis in the context of patient reported outcomes in Psychiatry. We present an overview of the main features of the Rasch analysis, using as an example the latent variable of depressive symptoms, with illustrations using the Beck Depression Inventory. We will show that with fitting data to the Rasch model, we can confirm the structural validity of the scale, including key attributes such as invariance, local dependency and unidimensionality. We also illustrate how the approach can inform on the meaning of the numbers attributed to scales, the amount of the latent traits that such numbers represent, and the consequent adequacy of statistical operations used to analyse them. We would argue that fitting data to the Rasch model has become the measurement standard for patient reported outcomes in general and, as a consequence will facilitate a quality improvement of outcome instruments in psychiatry. Recent advances in measurement technologies built upon the calibration of items derived from Rasch analysis in the form of computerized adaptive tests (CAT) open up further opportunities for reducing the burden of testing, and/or expanding the range of information that can be collected during a single session.

Translation and validation of the korean version of the 39-item Parkinson's disease questionnaire

Background and Purpose

The importance of health-related quality of life (HrQoL) has been increasingly emphasized when assessing and providing treatment to patients with chronic, progressive, degenerative disorders. The 39-item Parkinson's disease questionnaire (PDQ-39) is the most widely used patient-reporting scale to assess HrQoL in Parkinson's disease (PD). This study evaluated the validity and reliability of the translated Korean version of the PDQ-39 (K-PDQ-39).

Methods

One hundred and two participants with PD from 10 movement disorder clinics at university-affiliated hospitals in South Korea completed the K-PDQ-39. All of the participants were also tested using the Unified Parkinson's Disease Rating Scale (UPDRS), Korean version of the Mini-Mental State Examination (K-MMSE), Korean version of the Montgomery-Asberg Depression Scale (K-MADS), Epworth Sleepiness Scale (ESS) and non-motor symptoms scale (NMSS). Retests of the K-PDQ-39 were performed over time intervals from 10 to 14 days in order to assess test-retest reliability.

Results

Each K-PDQ-39 domain showed correlations with the summary index scores (rS=0.559-0.793, p<0.001). Six out of eight domains met the acceptable standard of reliability (Cronbach's α coefficient ≥0.70). The Guttman split-half coefficient value of the K-PDQ-39 summary index, which is an indicator of test-retest reliability, was 0.919 (p<0.001). All of the clinical variables examined except for age, comprising disease duration, levodopa equivalent dose, modified Hoehn and Yahr stage (H&Y stage), UPDRS part I, II and III, mood status (K-MADS), cognition (K-MMSE), daytime sleepiness (ESS) and (NMSS) showed strong correlations with the K-PDQ-39 summary index (p<0.01).

Conclusions

The K-PDQ-39 has been validated for use in the Korean-speaking PD population. The questionnaire is a valid and reliable assessment tool for assessing the HrQoL of Korean PD patients.

The factor structure of the SF-36 in adults with progressive neuromuscular disorders

OBJECTIVE

Quality of life (QoL) is an important consideration in the care of patients with chronic neuromuscular disorder (NMD). The current study sought to determine the factor structure of the Medical Outcomes Study Short-Form 36 (SF-36) version 2 in patients with NMD to determine the appropriateness of using this instrument to assess QoL in this clinical population.

METHODS

Confirmatory factor analyses were conducted on self-report SF-36 data from 245 individuals diagnosed with NMD. Six structural models of the SF-36 were evaluated against the participants' data.

RESULTS

The underlying factor structure of the SF-36 in NMD was observed to be consistent with contemporary theoretical models of the instrument. However, the traditional measurement model of SF-36 performed comparatively poorly.

CONCLUSION

The use of the SF-36 in individuals with NMD can be recommended when eight sub-scales are used and reported. However, the suggestion that the SF-36 can be usefully used as a two-sub-scale measure of physical health and mental health components in this clinical group was not supported because of model fit limitations.

Walking ability is a major contributor to fear of falling in people with Parkinson's disease: implications for rehabilitation

Although fear of falling (FOF) is common in people with Parkinson's disease (PD), there is a lack of research investigating potential predictors of FOF. This study explored the impact of motor, nonmotor, and demographic factors as well as complications of drug therapy on FOF among people with PD. Postal survey data (including the Falls Efficacy Scale, FES) from 154 nondemented people with PD were analyzed using multiple regression analyses. Five significant independent variables were identified explaining 74% of the variance in FES scores. The strongest contributing factor to FOF was walking difficulties (explaining 68%), followed by fatigue, turning hesitations, need for help in daily activities, and motor fluctuations. Exploring specific aspects of walking identified three significant variables explaining 59% of FOF: balance problems, limited ability to climb stairs, and turning hesitations. These results have implications for rehabilitation clinicians and suggest that walking ability is the primary target in order to reduce FOF. Specifically, balance, climbing stairs, and turning seem to be of particular importance.

Effects of parkinsonism on health status in welding exposed workers

BACKGROUND

Previous studies suggest that welders frequently display parkinsonian signs, such as bradykinesia and tremor. Demonstrating that these parkinsonian findings are associated with reductions in quality of life (QoL) or health status could have important repercussions for worker safety and performance.

METHODS

Subjects included 394 active workers exposed to welding fumes and evaluated for parkinsonism by movement disorders experts in a worksite-based epidemiology study. Subjects were diagnosed with parkinsonism if the Unified Parkinson Disease Rating Scale motor subsection part 3 (UPDRS3) score was ≥15. All subjects completed a Parkinson's disease (PD) symptom questionnaire and the PDQ39, a widely used QoL and health status measure for PD.

RESULTS

Total PDQ39 score and all subscores were greater in welders with parkinsonism than welders without parkinsonism, with the most significant differences observed for mobility, emotional well-being, and activities of daily living (ADL's). The PDQ39 scores for welding exposed workers with parkinsonism were similar to scores seen in a group of early PD patients.

CONCLUSION

Parkinsonism in active, welding exposed workers is associated with reductions in health status and QoL affecting a broad range of categories and within the range seen in early PD.

Pharmacotherapy in the management of early Parkinson's disease: cost-effectiveness and patient acceptability

In the absence of a cure, the primary goals in managing Parkinson's disease (PD) are to preserve functionality and health-related quality of life (HRQoL). Current therapeutic strategies for PD include symptomatic treatment and are primarily focused on replacing dopamine in the brain. Dopamine agonists can be used as an alternative initial levodopa therapy, to delay the onset of motor complications, but at the expense of more dopaminergic adverse effects; poorer control of motor symptoms; and increased cost. In PD, treatment effects and costs accumulate over time; hence the choice of time horizon in cost-effectiveness analysis can be particularly important. Pharmaceutical expenditures have grown rapidly in recent decades and now total nearly 10% of all health care costs. The main approach to treat PD at the present time is to advance knowledge of the efficacy, to reduce long-term complications associated with treatment, and to improve patient HRQoL and society burden. The implementation of cost-effectiveness studies, including the societal perspective, should be considered as an outcome of new therapy strategies, which would be helpful to health care decision makers.

Comparison of the effects of a physiotherapist-supervised exercise programme and a self-supervised exercise programme on quality of life in patients with Parkinson’s disease

Objectives: To compare the effects of a physiotherapist-supervised exercise programme in an exercise unit and self-supervised home exercise programme on quality of life in patients with Parkinson’s disease.

Design: Assessor-blinded, quasi-randomized trial (alternate allocation).

Setting: An outpatient exercise unit; home settings.

Participants: Thirty patients with idiopathic Parkinson’s disease, Hoehn & Yahr I—III, stable medication use.

Interventions: Patients were included in the physiotherapist-supervised or home group. The exercise programme was performed for 10 weeks, three times/week either under the supervision of a physiotherapist or at home without supervision.

Main outcome measures: Parkinson’s Disease Quality of Life Questionnaire (PDQLQ), Nottingham Health Profile (NHP), Unified Parkinson’s Disease Rating Scale (UPDRS), Beck Depression Inventory (BDI).

Results: Patients in the supervised physiotherapy group improved more than the home exercise group in Parkinson’s Disease Quality of Life Questionnaire (total score, Parkinson’s symptoms, emotional function), Nottingham Health Profile total, Unified Parkinson’s Disease Rating Scale (all domains) and Beck Depression Inventory scores.

Conclusions: The exercise programme under physiotherapist supervision was found to be more effective at improving activities of daily living, motor, mental, emotional functions and general health quality in patients with Parkinson’s disease compared with a self-supervised home programme.

Depressive symptoms impacting on health-related quality of life in early Parkinson's disease: results from Chinese L-dopa exposed cohort

OBJECTIVE

To investigate the impact of depressive symptoms on health-related quality of life (HR-QOL) in a group of patients with early Parkinson's disease (PD).

METHODS

A 20-item scale, the Center for Epidemiologic Studies Depression Scale (CESD) and a 36-item questionnaire, the medical outcomes study short form (SF-36) were administered as part of baseline assessment of a clinical trial in PD, enrolling 391 early-stage, L-dopa exposed PD patients in China. We used multiple regression models to examine the relationship of depressive symptoms, measured by the CESD with HR-QOL, as measured by the SF-36. The SF-36 score of the depressed patients was compared with those non-depressed, as well.

RESULTS

A total of 146 (37.3%) patients screened positive for depression. Compared with those non-depressed, depressed patients had lower scores in all dimensions of SF-36 profile (p<0.001). Multiple regression analysis revealed that depressive symptoms, measured by CESD, increased our ability to explain the variance of SF-36 total score by 34.5%. Additionally, depressive symptom is the only variable which has the predictive value not only for total SF-36 total score, but also for each subdimension score of SF-36 profile.

CONCLUSION

Depressive symptoms are common early in the disease, having a substantial impact on patients' HR-QOL, affecting many areas other than the obvious mental health dimension of the HR-QOL profile. Our results highlight the broad importance of treating depression in this population.

Whose quality of life? Ethical implications in patient-reported health outcome measurement

OBJECTIVES

Patient-reported health status questionnaires intend to assess illness and therapy from the patients' perspective. To provide fair and valid assessments, they should be equally relevant to major subsets of respondents. Furthermore, disease-specific measures are assumed to be perceived as more relevant than generic ones. This study assessed these assumptions among people with Parkinson's disease.

METHODS

Cross-sectional data from 202 people with Parkinson's disease (54% men; mean age, 70) were analyzed regarding patient-rated relevance and predictors of patient-rated poor relevance of two generic [the 36-item Short Form Health Survey (SF-36) and Nottingham Health Profile (NHP)] and one disease-specific [Parkinson's Disease Questionnaire (PDQ-39)] health status questionnaire.

RESULTS

There were no differences in relevance ratings across the questionnaires. Poorer overall quality of life [odds ratio (OR), 2.459] and mental health (OR, 1.023) were associated with poorer patient-rated relevance of the SF-36, and higher age was associated with poorer patient-rated relevance of the PDQ-39 (OR, 1.040). No significant predictors were found for the NHP.

CONCLUSIONS

The PDQ-39 failed to meet the assumption that disease-specific scales are more relevant than generic ones. Nevertheless, the most important implication of this study is an ethical one. Because the relevance of the SF-36 and PDQ-39 is perceived as poorer by those who fare least well and by older people, these scales may not reflect the perspectives of these groups. This challenges bioethical principles and threatens scientific validity. Perceived relevance of patient-centered outcomes needs to be considered, or the voice of vulnerable groups may be silenced, fair inferences prohibited, and opportunities for improved care lost.

The factor structure of the SF-36 in Parkinson's disease

RATIONALE, AIMS AND OBJECTIVES

The concept of quality of life (QoL) has emerged as an important psychological dimension in individuals experiencing Parkinson's disease (PD). The current study sought to determine the factor structure of the Medical Outcomes Study Short-Form 36 (SF-36) version 2 in patients with PD in order to evaluate how this measure might best be used to assess QoL in this clinical population.

METHOD

Confirmatory factor analyses were conducted on self-report SF-36 data from 339 individuals diagnosed with PD. Six structural models of the SF-36 were evaluated against the participants' data.

RESULTS

The underlying factor structure of the SF-36 in PD was observed to be inconsistent with the assumed measurement model of SF-36 but consistent with contemporary theoretical models of the instrument.

CONCLUSIONS

The use of the SF-36 in individuals with PD can be recommended when eight subscales are used and reported. Evidence to support the use of the instrument as a two-subscale measure of physical health and mental health components was not found.

Cost effectiveness of pharmacotherapies in early Parkinson's disease

Parkinson's disease is one of the most common chronic neurodegenerative diseases. The progression of disease and the psychosocial consequences exert a major impact on patients' health-related quality of life. Although levodopa provides the best symptomatic benefit with the fewest short-term adverse effects, long-term treatment results in motor complications that are associated with both higher costs and considerable increase in patients' discomfort. The introduction of dopamine agonists early in the treatment of Parkinson's disease leads to a delay of these motor complications, but the treatment is associated with higher costs.In this review we evaluate available cost-effectiveness analyses of the dopamine agonists pramipexole, pergolide, bromocriptine, ropinirole, cabergoline and levodopa in the treatment of early Parkinson's disease. Considerable methodological differences in the identified studies complicate a comparison and impede clear evidence as to which dopamine agonist treatment is the most cost effective in early Parkinson's disease. Novel head-to-head comparisons considering the actual treatment guidelines are necessary to identify the most cost-effective alternative in treating de novo Parkinson's disease patients.

Predictors and course of health-related quality of life in Parkinson's disease

We investigated how health related quality of life (HRQL) changes over time in a population-based cohort of patients with Parkinson's disease (PD), and which factors predict a lower level of HRQL in these patients. Of 227 patients with PD assessed at baseline and followed prospectively, information on HRQL-status was obtained in 111 subjects 4 years and 82 patients 8 years after inclusion. HRQL was measured by the Nottingham Health Profile (NHP). Analyses were conducted using generalized estimating equation models. The NHP total score (P < 0.001) and scores in all NHP dimensions except for sleep worsened significantly during follow-up. Steepest slope was found for the domain physical mobility (3.16, 95% CI 2.39-3.92), followed by the domains social isolation (2.22, 95% CI 1.52-2.93) and emotional reactions (1.36, 95% CI 0.74-1.97). In addition to follow-up time, higher Hoehn and Yahr staging, higher Montgomery and Aasberg Depression Rating Scale scores, and presence of insomnia at baseline were associated with lower levels of overall HRQL during follow-up. We conclude that PD has an increasing impact on HRQL as the disease progresses. During long-term follow-up, deterioration in physical mobility was the most important single factor contributing to decline in HRQL in our cohort, although distress of nonmotor character as a whole outweighed the impact of distress in physical mobility on overall HRQL. More advanced disease, higher severity of depressive symptoms, and presence of insomnia were found to be important and independent predictors of poor HRQL. (c) 2008 Movement Disorder Society.

Cross-diagnostic validity of the Nottingham Health Profile Index of Distress (NHPD)

Background

The Nottingham Health Profile index of Distress (NHPD) has been proposed as a generic undimensional 24-item measure of illness-related distress that is embedded in the Nottingham Health Profile (NHP). Data indicate that the NHPD may have psychometric advantages to the 6-dimensional NHP profile scores. Detailed psychometric evaluations are, however, lacking. Furthermore, to support the validity of the generic property of outcome measures evidence that scores can be interpreted in the same manner in different diagnostic groups are needed. It is currently unknown if NHPD scores have the same meaning across patient populations. This study evaluated the measurement properties and cross-diagnostic validity of the NHPD as a survey instrument among people with Parkinson's disease (PD) and peripheral arterial disease (PAD).

Methods

Data from 215 (PD) and 258 (PAD) people were Rasch analyzed regarding model fit, reliability, differential item functioning (DIF), unidimensionality and targeting. In cases of cross-diagnostic DIF this was adjusted for and the impact of DIF on the total score and person measures was assessed.

Results

The NHPD was found to have good overall and individual item fit in both disorders as well as in the pooled sample, but seven items displayed signs of cross-diagnostic DIF. Following adjustment for DIF some aspects of model fit were slightly compromised, whereas others improved somewhat. DIF did not impact total NHPD scores or resulting person measures, but the unadjusted scale displayed minor signs of multidimensionality. Reliability was > 0.8 in all within- and cross-diagnostic analyses. Items tended to represent more distress (mean, 0 logits) than that experienced by the sample (mean, -1.6 logits).

Conclusion

This study supports the within- and cross-diagnostic validity of the NHPD as a survey tool among people with PD and PAD. We encourage others to reassess available NHP data within the NHPD framework to further evaluate the strengths and weaknesses of this simple patient-reported index of illness-related distress.