title: Handling missing values in the MDS-UPDRS.
abstract: This study was undertaken to define the number of missing values permissible to render valid total scores for each Movement Disorder Society Unified Parkinson's Disease Rating Scale (MDS-UPDRS) part. To handle missing values, imputation strategies serve as guidelines to reject an incomplete rating or create a surrogate score. We tested a rigorous, scale-specific, data-based approach to handling missing values for the MDS-UPDRS. From two large MDS-UPDRS datasets, we sequentially deleted item scores, either consistently (same items) or randomly (different items) across all subjects. Lin's Concordance Correlation Coefficient (CCC) compared scores calculated without missing values with prorated scores based on sequentially increasing missing values. The maximal number of missing values retaining a CCC greater than 0.95 determined the threshold for rendering a valid prorated score. A second confirmatory sample was selected from the MDS-UPDRS international translation program. To provide valid part scores applicable across all Hoehn and Yahr (H&Y) stages when the same items are consistently missing, one missing item from Part I, one from Part II, three from Part III, but none from Part IV can be allowed. To provide valid part scores applicable across all H&Y stages when random item entries are missing, one missing item from Part I, two from Part II, seven from Part III, but none from Part IV can be allowed. All cutoff values were confirmed in the validation sample. These analyses are useful for constructing valid surrogate part scores for MDS-UPDRS when missing items fall within the identified threshold and give scientific justification for rejecting partially completed ratings that fall below the threshold.
authors: Department of Neurological Sciences, Rush University Medical Center, Chicago IL, USA.
authors: Christopher G
authors: CG
authors: Goetz
authors: Division of Biostatistics, School of Public Health, University of Texas Health Science Center at Houston, Houston, TX, USA.
authors: Sheng
authors: S
authors: Luo
authors: Division of Biostatistics, School of Public Health, University of Texas Health Science Center at Houston, Houston, TX, USA.
authors: Lu
authors: L
authors: Wang
authors: Division of Biostatistics, School of Public Health, University of Texas Health Science Center at Houston, Houston, TX, USA.
authors: Barbara C
authors: BC
authors: Tilley
authors: Division of Preventive and Behavioral Medicine, University of Massachusetts, Worcester, MA, USA.
authors: Nancy R
authors: NR
authors: LaPelle
authors: Department of Neurological Sciences, Rush University Medical Center, Chicago IL, USA.
authors: Glenn T
authors: GT
authors: Stebbins
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016208:Databases, Factual / Q000706:statistics & numerical data; D004185:Disability Evaluation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000175:diagnosis* / Q000503:physiopathology; D015203:Reproducibility of Results; D012107:Research Design; D012720:Severity of Illness Index; D012955:Societies, Medical / Q000592:standards*
keywords: Lin's correlation coefficient; MDS-UPDRS; Parkinson's disease; missing values; rating scales
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