title: Alzheimer disease with psychosis: excess cognitive impairment is restricted to the misidentification subtype.
abstract: OBJECTIVE
  Psychotic symptoms occur in 30%-60% of individuals with Alzheimer disease (AD) with psychosis (AD+P). AD+P identifies a distinct AD phenotype, with increased severity of cognitive impairment and a more rapid cognitive decline. Using factor and cluster analysis, we previously proposed two subtypes of patients with AD+P, one characterized by misidentifications and hallucinations (Misidentification), the other by persecutory delusions (Paranoid). We hypothesized that these two groups differed in their patterns of cognitive impairment, compared with AD subjects without psychosis.
  
  
  METHODS
  Subjects (N=119) with possible or probable AD were assessed with a comprehensive neuropsychological test battery at the time of initial presentation. Psychotic symptoms were ascertained with the CERAD Behavioral Rating Scale. Cognitive test scores were compared among groups by use of general linear-regression models, with age, education, and duration of illness entered as covariates. All results were corrected for multiple comparisons.
  
  
  RESULTS
  The Misidentification group was significantly more impaired than the Non-Psychotic group on tests of verbal fluency and visuospatial function. The Paranoid group did not differ from the Non-Psychotic group on any test.
  
  
  CONCLUSIONS
  These results support the identification of the Misidentification and Paranoid groups as distinct subgroups of AD+P. The ability to detect meaningful biologic associations of AD+P in future studies would be enhanced by separate analysis of the Misidentification and Paranoid phenotypes.
authors.affiliation: Dept. of Psychiatry, Univ. of Pittsburgh, PA, USA.
authors.forename: Gina
authors.initials: G
authors.lastname: Perez-Madriñan
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Cook
authors.forename: Judith A
authors.initials: JA
authors.lastname: Saxton
authors.forename: Sachiko
authors.initials: S
authors.lastname: Miyahara
authors.forename: Oscar L
authors.initials: OL
authors.lastname: Lopez
authors.forename: Daniel I
authors.initials: DI
authors.lastname: Kaufer
authors.forename: Howard J
authors.initials: HJ
authors.lastname: Aizenstein
authors.forename: Steven T
authors.initials: ST
authors.lastname: DeKosky
authors.forename: Robert A
authors.initials: RA
authors.lastname: Sweet
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000150:complications* / Q000175:diagnosis; D003072:Cognition Disorders / Q000145:classification* / Q000175:diagnosis / Q000453:epidemiology*; D015897:Comorbidity; D003702:Delusions / Q000453:epidemiology; D003710:Demography; D003937:Diagnosis, Differential; D003951:Diagnostic Errors; D005260:Female; D006801:Humans; D008297:Male; D009483:Neuropsychological Tests; D010259:Paranoid Disorders / Q000175:diagnosis / Q000453:epidemiology; D010641:Phenotype; D011618:Psychotic Disorders / Q000150:complications*; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires