Value and appropriate use of rating scales and apparative measurements in quantification of disability in Parkinson's disease

Despite widespread use in pharmacotherapeutical trials, in the majority of rating scales used in Parkinson's disease (PD) validity, reliability and appropriate use have never been confirmed by statistical data. For this reason 350 unselected PD-pats. were investigated by an extensive standardized test-battery including registration of basis data, Columbia University Rating Scale (CURS), scale for assessment of functional disability (ADL), SCAG-scale, Hoehn & Jahr-scale (HY), mod. Webster step second-test (WSST), Purduepegboard, questionnaire for subjective complaints (SC), WDG, LPS1/2, 3/4, 6, 7, 10, clinical assessment of dementia, v. Zerssen-scale and orthostatic hypotension (60° tilt up). For CURS, SCAG and ADL instrumental reliability was calculated by Cronbach's alpha. For CURS, SCAG, ADL and the total data of complete test battery (CTB) principal component analysis (PCA) was performed for data reduction. CURS, SCAG and ADL showed high internal consistency (alpha ∼≥0.9). For CURS 5 factors accounting for 66% total variance could be extracted by PCA. They represent gait, rigidity, tremor, right/left dexterity (eigenvalues >1). For SCAG 3 factors (61% of total variance) representing dementia, depression and change of personality were extracted. For ADL 3 factors (67% of total variance) could be extracted, representing overall functional disability, handwriting and disablity by pain. PCA of the CTB identified 8 interpretable factors (66% of total variance) characterizing at least partially the clinical profile of PD: 1. motor disability (assessment by rating-scales) 2. dementia, 3. motor-disability (assessment by apparative measurements), 4. depression, 5. orthostatic hypotension, 6. WDG, 7. tremor and 8. pain. Our data confirm the suitability of the investigated scales and give a rational base for their appropriate use in a sense of data reduction and economical evaluation.