Towards a Parkinson-specific gait, balance, and posture rating scale: development and validation testing plan of complementary investigator-rated and patient-reported items.

A high number of people with Parkinson*s disease (PD) develop one or more axial
disorders, such as postural abnormalities, balance, and/or gait disorders.
These disorders often result in falls, concerns about falling, and a reduced
quality of life. Adequate and timely recognition of these disorders is,
therefore, essential to identify patients at risk of falling, but also to
evaluate efficacy of symptomatic (non-) pharmacological interventions in daily
clinical practice and research settings. In 2016, the Movement Disorder
Society (MDS) Task Force on Rating Scales commissioned a critique of existing
clinical rating scales and questionnaires used in PD, and concluded that none
of the existing scales could adequately and separately assesses the required
constructs (i.e., gait - including freezing of gait -, balance, and posture. To
overcome this limitation, it was recommended that an ideal future scale should,
therefore, include separate sections for gait, balance, and posture, and should
specifically address freezing of gait and fear of falling.

The aim of this study is to develop and validate this much-needed Parkinson*s
Disease-specific rating scale; the so-called *Movement Disorders Society Rating
Scale: Postural Instability and Gait Difficulties (PIGD)*. This PIGD rating
scale assesses the constructs gait (including freezing of gait), balance,
posture, and concerns about falling separately. The scale consists of
investigator-rated and patient-reported outcomes.

This study is a multi-centre validation study. The study comprises of three
subsequent parts:
Part 1: item development: A pool of possible items is drafted based on the
literature and focus groups with clinical experts and public and patient
involvement.
Part 2: scale development: fifteen persons with PD, in addition to fifteen
health care providers are asked to participate at the Radboudumc Nijmegen (NL)
to pilot the pool of possible items. Participants are asked to participate in a
single session to perform the newly developed PIGD rating scale. The assessment
will last 60-75 minutes. A preliminary psychometric analysis (item reduction
analysis) will be performed to adjust the pool of possible items.
Part 3: scale evaluation: A total of 300 persons with PD will be including
among the participating centres (Radboudumc Nijmegen (NL), University of
Portland (USA), Brain and Mind Centre Sydney (AUS), University of Waterloo
(CAN), Emory University School of Medicine (USA), and Newcastle University
(UK)). Of the 300 patients, 75 of them will be included at Radboudumc Nijmegen
(NL).
Furthermore, 250 patients are asked to participate once, whereas 50 patients
will be asked to participate twice (in order to evaluate test-retest
reliability). Of these 50 patients, approximately 12-15 (25%) of them will be
included at the Radboudumc Nijmegen (NL). Each assessment will last 60-75
minutes.

Benefits: Participants will not directly benefit from participating in this
study.
Burden: The assessments will last 60-75 minutes.
Risks: People with PD are generally exposed to an increased risk of falls
compared to age-matched controls. As this study is a validation study and no
intervention is introduced, we do not expect additional risks within this
study. The individual items of the concept PIGD Rating Scale are inspired by
clinical balance and gait tasks that are part of routine assessment.