Louis C. S. Tan

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Previous validation studies on the PDQ-8, a brief disease-specific quality of life instrument, were performed with the PDQ-8 nested in the original PDQ-39. Such an approach may influence patient responses and the psychometric properties of the PDQ-8. We therefore undertook this study to validate the PDQ-8 when administered independently in English and(More)
To develop a function for mapping the eight-item Parkinson’s Disease Questionnaire (PDQ-8) to the EuroQol Group’s EQ-5D utility index. Data from two surveys of 324 patients with Parkinson’s disease was divided into two groups. One was used to estimate the mapping functions by regression methods and the other was used to validate the mapping functions. A(More)
To determine the frequency and spectrum of complementary therapy (CT) use and its association with sociodemographic or disease-specific characteristics among Asian patients with Parkinson's disease (PD) in Singapore, we interviewed 159 patients using a structured questionnaire. Sixty-one percent (95% CI=55-67) of participants used at least one type of CT(More)
The purpose of this study was to evaluate the responsiveness of the EQ-5D and the Parkinson’s Disease Questionnaire (PDQ-8) to deterioration in health-related quality of life (HRQoL) in patients with Parkinson’s disease (PD). HRQoL and clinical data collected from 31 patients with PD (male: 74.2%, mean age: 61 years) who were surveyed with the EQ-5D and the(More)
Depression, anxiety and apathy are common mood disturbances in Parkinson's disease (PD) but their pathophysiology is unclear. Advanced neuroimaging has been increasingly used to unravel neural substrates linked to these disturbances. A systematic review is provided of neuroimaging findings in depression, anxiety and apathy in PD. A PubMed, MEDLINE and(More)
OBJECTIVE To study the interaction between levodopa and the feedback process on set-shifting in Parkinson's disease (PD). METHODS Functional magnetic resonance imaging (fMRI) studies were performed on 13 PD subjects and 17 age-matched healthy controls while they performed a modified card-sorting task. Experimental time periods were defined based on the(More)
BACKGROUND Early diagnosis of cognitive impairment in PD would allow appropriate monitoring and timely intervention to reduce the progression to dementia (PDD). OBJECTIVE To study the usefulness of the Montreal Cognitive Assessment (MoCA) in the screening for mild cognitive impairment (PD-MCI) and its predictive utility in determining longitudinal(More)
Objective: The purpose of the study was to validate the Chinese (Singapore) version of the Parkinson’s Disease Questionnaire (PDQ-39CSV) and its briefer version (PDQ-8CSV). Methods: A convenience sample of Chinese-speaking Singaporeans with Parkinson’s disease (PD) (n=63) completed a questionnaire containing the PDQ-39CSV and the Chinese (Singapore) EQ-5D.(More)
Parkin gene mutations have been detected in families with early-onset autosomal recessive parkinsonism. We report a novel heterozygous 40 base pair deletion in exon 3 of the parkin gene that increases the susceptibility of carriers to develop parkinsonism/dystonia and manifests remarkable variability in regard to age of onset and phenotype in a single(More)