title: Is the Parkinson Anxiety Scale comparable across raters?
abstract: The Parkinson Anxiety Scale is a new scale developed to measure anxiety severity in Parkinson's disease specifically. It consists of three dimensions: persistent anxiety, episodic anxiety, and avoidance behavior. This study aimed to assess the measurement properties of the scale while controlling for the rater (self- vs. clinician-rated) effect. The Parkinson Anxiety Scale was administered to a cross-sectional multicenter international sample of 362 Parkinson's disease patients. Both patients and clinicians rated the patient's anxiety independently. A many-facet Rasch model design was applied to estimate and remove the rater effect. The following measurement properties were assessed: fit to the Rasch model, unidimensionality, reliability, differential item functioning, item local independency, interrater reliability (self or clinician), and scale targeting. In addition, test-retest stability, construct validity, precision, and diagnostic properties of the Parkinson Anxiety Scale were also analyzed. A good fit to the Rasch model was obtained for Parkinson Anxiety Scale dimensions A and B, after the removal of one item and rescoring of the response scale for certain items, whereas dimension C showed marginal fit. Self versus clinician rating differences were of small magnitude, with patients reporting higher anxiety levels than clinicians. The linear measure for Parkinson Anxiety Scale dimensions A and B showed good convergent construct with other anxiety measures and good diagnostic properties. Parkinson Anxiety Scale modified dimensions A and B provide valid and reliable measures of anxiety in Parkinson's disease that are comparable across raters. Further studies are needed with dimension C.
authors.affiliation: National School of Public Health, Institute of Health Carlos III and REDISSEC, Madrid, Spain.
authors.forename: Maria João
authors.initials: MJ
authors.lastname: Forjaz
authors.forename: Alba
authors.initials: A
authors.lastname: Ayala
authors.forename: Pablo
authors.initials: P
authors.lastname: Martinez-Martin
authors.forename: Kathy
authors.initials: K
authors.lastname: Dujardin
authors.forename: Gregory M
authors.initials: GM
authors.lastname: Pontone
authors.forename: Sergio E
authors.initials: SE
authors.lastname: Starkstein
authors.forename: Daniel
authors.initials: D
authors.lastname: Weintraub
authors.forename: Albert F G
authors.initials: AF
authors.lastname: Leentjens
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001008:Anxiety Disorders / Q000175:diagnosis* / Q000209:etiology*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007391:International Cooperation; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000150:complications*; D011569:Psychiatric Status Rating Scales; D011594:Psychometrics / Q000379:methods; D012044:Regression Analysis; D012720:Severity of Illness Index
keywords: Parkinson's disease; Rasch analysis; anxiety; rater