Ires Ghielen

130 Chapter 7 Secondary outcome measures 1. The Parkinson’s Disease Questionnaire-39 (PDQ-39) This questionnaire is a measure of quality of life adapted for people with PD [38]. It consists of 39 statements that cover eight domains associated with health, such as mobility and emotionality, that can be influenced by PD. Patients can reply by ticking the relevant answer that indicates whether they experienced problems during the past month (five boxes from ‘never’ to ‘always’). The PDQ-39 is a valid and reliable instrument for patients with PD [38,39]. 2. The Wearing-off Questionnaire 19 (WOQ-19) In this 19 items questionnaire [31], PD patients indicate which symptoms they experience and whether these symptoms improve after administration of PD medication. 3. Beck Anxiety Inventory (BAI) This self-report questionnaire consists of 21 common symptoms of anxiety [32]. Patients indicate how much they have been bothered by these symptoms during the past week, including today. 4. Beck Depression Inventory (BDI) This 21-item self-report questionnaire measures whether patients experience depressive symptoms [40]. Patients indicate the statements that are most applicable to their own situation during the past week, including today. 5. 10 Meter Walk Test (10MWT) To measure comfortable walking speed, the patients are asked to walk 10 metres, which are characterized by a starting and a finishing point [41]. The researcher measures the time needed to cover this distance. 6. Timed One Leg Stance Test (OLST) This test measures balance by asking the patients to stand on one leg without help [42]. The number of seconds that the patients maintain their balance is noted, with a maximum of 60 seconds. 7. The Nottingham Extended Activities of Daily Living (NEADL) index This 22-item self-report questionnaire covers four aspects of daily living: mobility, activities in the kitchen, domestic tasks, and leisure activities [43]. Patients indicate whether they independently performed activities during the past weeks.