PDQ-8: A Simplified and Effective Tool Measuring Life Quality in Progressive Supranuclear Palsy

INTRODUCTION

Progressive supranuclear palsy (PSP) is a progressive neurodegenerative disorder, characterized by supranuclear vertical gaze palsy, repeated falls, levodopa-unresponsive parkinsonism, and cognitive disturbances [1]. Without effective therapy, these motor and non-motor symptoms severely impair the life quality of the patients. Therefore, the self-reported quality of life (QoL) should be carefully listened to and considered before making clinical assessments and therapeutic explorations, from the patient-centered perspective.

So far, the most commonly used tools on QoL in PSP include the Progressive Supranuclear Palsy Quality of Life Scale (PSP-QoL) [2], the Parkinson’s Disease Questionnaire-39 (PDQ-39) [3], and the EuroQol instrument (EQ-5D) [4, 5]. PSP-QoL scale was designed as a specific measure of health status in PSP, including physical and mental domains [2]. PDQ-39, though designed specifically for Parkinson’s disease (PD) [6–9], was also used in atypical parkinsonism including PSP [2, 11], to compare QoL among different diseases sometimes. However, both questionnaires take long time to complete, limiting their clinical practice, especially in the severely ill patients, online consultations and longitudinal follow-ups [12]. Finding an appropriate simplified QoL questionnaire was also badly in need to follow up chronic and progressive diseases during COVID-19 period.

As far as we know, there has been no short QoL context specially designed for PSP yet. PDQ-8, which is composed of eight representative questions from PDQ-39 [13], is the only available and widely used short QoL tool related to parkinsonism. Because PDQ-8 could shorten the filling time and increase the completion rate, it is preferred in the use of mobile app and follow-up in PD [14]. It has also been put into use as the vital endpoint in diverse PD clinical experiments [15–19]. Nevertheless, whether PDQ-8 could be used in assessing the QoL in PSP has not been assessed yet.

In this study, we explored the detailed profiles and related determinants of QoL in PSP by several QoL measurements in a relatively large cohort. Furthermore, we aimed to validate whether PDQ-8, the only simplified QoL tool in Parkinsonism, could be applied in assessing the QoL in PSP.

METHODS

RESULTS

DISCUSSION

In our relatively large PSP cohort, three major findings on the QoL in patients with PSP were reported. First, the patients with PSP showed more or less impairment in quality of life physically and mentally evaluated by PSP-QoL, presenting a multiple-domain lesion pattern in PDQ-39, with mobility, ADL, cognition and communication most severely involved. Second, as the only widely accepted short QoL measurement tool in PD [15–19] and related disorders, PDQ-8 was comparable to PSP-QoL in assessing the QoL in PSP, which could be further used in the future clinical practices. Last but not least, the disease severity (PSPrs), depression (GDS) and daytime sleepiness (ESS) may be critical determinants on the QoL burdens (assessed by PSP-QoL or PDQ-8) in PSP. This study may provide useful information in assessing the quality of life and treatment response in PSP.

In the current study, there were no floor effect in all the QoL tools. Although a broad spectrum of clinical manifestation could contribute to individual variation in QoL impairment, we found almost every patient reported physical and mental problems from PSP-QoL. Meanwhile, all the patients with PSP reported at least one QoL domain impaired evaluated by PDQ-39, most severely impaired in the domains of mobility, ADL, cognition and communication, in contrast to PD with physical discomfort and stigma domains mainly affected [21]. These findings were also similar to our previous report in MSA-P [21] and other report in PSP [3] respectively. Furthermore, the patients with PSP-RS reported more severe QoL lesions than the PSP-non-RS ones physically and mentally, also shown in the PDQ-39 domains of mobility, ADL, emotional well-being and cognition. The findings in the self-reported QoL were in consistent with the results from physicians-evaluated motor and non-motor scales, and they were supported by the idea that PSP-RS was the final stage with most severe lesions in the clinical trajectories of PSP [1, 22].

It is noteworthy that here not only did we use the specific-designed PSP-QoL in the cohort, but we also applied the PDQ-39 questionnaire to acquire more specific information of QoL subdomains impairment, as a few of other publications did [2, 11]. In addition, we and other reports [2] proved a strong correlation between PDQ-39 and PSP-QoL subscales (physical and mental). Crucially, we admitted that PDQ-39 was not designed for PSP. Some frequently experienced symptoms in PSP, such as ocular motor dysfunction, muddled thinking, confusion and apathy are not precisely addressed in this PD-specific life quality questionnaire [23]. Therefore, if time and conditions permit, the quality of life of PSP patients should be evaluated by the more specialized PSP-QoL [2, 24]. However, it was impossible for some advanced patients (e.g., with dementia or failing to express themselves) to complete the 30-min questionnaires [12], not to mention those patients in the remote follow-up, which was common during COVID-19 period.

In that case, we aimed to find a valid, simple, quick to complete and easy to score QoL instrument, which was still a vacancy in PSP. As a simplified questionnaire of PDQ-39, PDQ-8 was easy for patients to understand, with high completion rate. Therefore, it was preferred in the longitudinal follow-up and online self-report consultations [15–19]. Nevertheless, it has not been proved to be valid and reliable in patients with PSP, which was necessary. Currently, we preliminarily validated the effectiveness of PDQ-8 in assessing QoL in PSP and different subtypes through item-to-dimension correlations. The profiles of QoL burden assessed by PSP-QoL and PDQ-39, could also be successfully recaptured by PDQ-8 in our cohort. Therefore, we supported that PDQ-8 could be carefully and effectively used in PSP.

In further analysis, disease severity, depression and daytime sleepiness were classified as critical determinants to the QoL (evaluated either by PSP-QoL or PDQ-8) in PSP. Our data were in consistent with the previous reports of great association between PSPrs and PSP-QoL [24], while verified that non-motor symptoms also play an important role in the quality of life [25–28]. In particular, depression may impose a heavy QoL burden on the patients with PSP [29–31]. It has been previously reported that depression should be carefully evaluated, as it was a common determinant to QoL in neurodegenerative disorders, such as PD [21, 32] and MSA [3, 33]. In general, patients with PSP are more prone to depression than MSA [4, 5]. Additionally, depression has been identified as a possible predictor of shorter survival in PSP [34], emphasizing the importance of paying attention to mental health and administering antidepressant therapy. The depressive symptoms may be related not only to disease-related changes in brain function, but also to the functional consequences of the disease. As for sleep disturbance, it has been reported as a most severe non-motor symptoms in PSP [35], with more sleep architecture abnormalities and insomnia than other neurodegenerative disorders. Such sleep disturbances may be due to the atrophy of pontine tegmental nuclei [35].

In our previous study, we validated the use of PDQ-8 in Chinese patients with PD [36], and adopted it as a primary endpoint in the multi-center real-world study (clinical trails ID: NCT03649503). Moreover, we developed a PAWEI remote medical system/app for the longitudinal follow-up in PD, in which the PDQ-8 was adopted. This telemedicine system was successfully run for the remote medical consultation during this COVID-19 pandemic time. After the current validation, we will further explore the use of PDQ-8 in telemedical system for assessing QoL in PSP. We also look forward to the invention of PSP-specific simplified QoL instrument or the improved PDQ-8 in the future. We believe this timely feedback from patients can serve as a reminder for physicians and their caregivers, which could also be carefully considered as the endpoint of clinical trails in PSP.

As we know, this was the first study validating the application of PDQ-8 in a relatively large PSP cohort. Some limitations should be admitted here. First, despite the large sample size, this cohort was in the single hospital with all Asian patients included. Second, the nature of the QoL assessment was self-reported, so we could not rule out the participants-related bias to the study. Third, the diagnosis of PSP was made cross-sectionally, and the longitudinal follow-up will be helpful for validating our findings. In addition, we should always keep in mind the PDQ-8 was not specifically designed for PSP. The exact effectiveness of using PDQ-8 in PSP and the development of modified short-version of PSP-QoL need to be further explored in the future. Last but not least, we raised the possibility of using PDQ-8 to assess QoL through the PAWEI telemedicine system. However, we should be aware of its limitation in some aspects that are different between patients with PD and patients with atypical parkinsonism.