A large randomised long-term assessment of the relative effectiveness of surgery for Parkinson's Disease (PD)

Patient's self-evaluation of functional status (using the PDQ-39 questionnaire). It is important that the trial assesses the patients' own perceptions of their functioning and addresses matters of most concern to them. The PDQ-39 is a self-completed questionnaire, specifically developed and tested for use in clinical trials by two of the applicants/collaborators. It reflects patients' concerns in eight aspects of PD: mobility, activities of daily living, emotional well-being, stigma, social support, cognition and bodily discomfort. It has been extensively tested for validity, reproducibility and sensitivity. Affective and cognitive changes are detected by PDQ-39

1. Quality of life. In addition to PDQ-39, the EuroQoL EQ-5D will be used as the main outcome measure for the Health Economic evaluation (see below) as this permits incremental quality adjusted life-years (QALYs) to be calculated.
2. Dementia screen. The trial aims to determine whether therapies prevent or decrease the decline of cognitive function as measured by the DRS-II. The DRS has the ability to assess the level of cognitive impairment in different clinical populations and to differentiate between types of dementia.
3. Clinical assessment of functioning. The Unified Parkinson's Disease Rating Scale (UPDRS - both on and off drug therapy) and Hoehn & Yahr staging system will provide a standard neurological assessment against which to validate further the PDQ-39 in a subset of patients.
4. Neuropsychology. A semi-structured neuropsychiatric interview and psychometric measures of depression/anxiety, and cognition (pre-morbid/current IQ, language, attention-executive functions, memory and spatial skills) in a subset of patients.
5. Burden on carers. Little is known about the effects of PD and its treatment on carers. The person identified by the patient as their primary carer, if they have one, will be asked to complete the SF36, a well validated measure of health status.
6. Institutionalisation rates and other measures of individual and societal cost.
7. Toxicity and side-effects of surgery, including mortality, stroke and other serious adverse events. Toxicity and side-effects of medical therapy will also be recorded.
8. Death from all causes and specifically from PD and the surgical procedure. Patients will be flagged with the Office for National Statistics (ONS) for long-term mortality follow-up.
Some centres will wish to undertake additional investigations (e.g. more detailed clinical assessments, including video records, neuropsychology, physiology and imaging) and we will encourage such scientific add-on studies, although they will not be part of the main trial.