title: Spectrum Effect and Spectrum Bias in the Screening Test Performance for Amnestic Mild Cognitive Impairment: What are the Clinical Implications?
abstract: BACKGROUND
  A single cutoff is widely used to screen amnestic mild cognitive impairment (aMCI). However, results of screening test performance are never adjusted for spectrum effect and spectrum bias.
  
  
  OBJECTIVE
  To assess the potential impact of spectrum effect and spectrum bias on screening test performance and clinical decision.
  
  
  METHODS
  The ability of the combination of Memory Impairment Screen (MIS), the Isaacs Set Test (IST), and the Mini-Mental State Examination (MMSE) to distinguish aMCI (n = 3,330) from patients with subjective cognitive complaints (SCC) (n = 1,522) was investigated across a wide range of age and educational backgrounds. The spectrum effect was defined as the variation of the sensitivity and/or the specificity across different subgroups. A spectrum bias was highlighted if the likelihood ratio (LR) observed in a subgroup of subjects statistically differed from the LR observed in the overall sample.
  
  
  RESULTS
  For the MIS-IST pairing, the overall sensitivity and specificity were equal to 72.5% and 75.2% , the positive LR (LR+) and the negative LR (LR-) were equal to 2.91 and 0.37, respectively. Across the different age-education subgroups, the sensitivities ranged from 43.7% to 92.5% and specificities from 39.3% to 95.2%. LR+ and LR- ranged from 1.51 to 9.10 and 0.13 to 0.59, respectively. A statistically significant spectrum bias was found in some subgroups and may result in differences between the post-test probabilities. Similar results were also found for the MMSE.
  
  
  CONCLUSIONS
  These findings could potentially affect the clinician's decision with a possible greater impact in elderly patients with a lower educational level.
authors.affiliation: Department of Neurology, Besançon University Hospital, Besançon, France.|Department of Clinical Psychiatry, Besançon University Hospital, Besançon, France.|Rapid-Fr network (Regional Network for Diagnostic Aid and Management of Patients with Cognitive Impairment - Department of Franche-Comté), Besançon, France.|EA 481 Laboratory of Neurosciences, University of Franche-Comté, Besançon, France.
authors.forename: Gilles
authors.initials: G
authors.lastname: Chopard
authors.affiliation: Clinical Methodology Center, Besançon University Hospital, Besançon. France.
authors.forename: Marc
authors.initials: M
authors.lastname: Puyraveau
authors.affiliation: Rapid-Fr network (Regional Network for Diagnostic Aid and Management of Patients with Cognitive Impairment - Department of Franche-Comté), Besançon, France.
authors.forename: Mickael
authors.initials: M
authors.lastname: Binetruy
authors.affiliation: Rapid-Fr network (Regional Network for Diagnostic Aid and Management of Patients with Cognitive Impairment - Department of Franche-Comté), Besançon, France.
authors.forename: Agatha
authors.initials: A
authors.lastname: Meyer
authors.affiliation: Department of Clinical Psychiatry, Besançon University Hospital, Besançon, France.|Rapid-Fr network (Regional Network for Diagnostic Aid and Management of Patients with Cognitive Impairment - Department of Franche-Comté), Besançon, France.|EA 481 Laboratory of Neurosciences, University of Franche-Comté, Besançon, France.|CIC-IT Inserm, Besançon University Hospital, Besançon, France.
authors.forename: Pierre
authors.initials: P
authors.lastname: Vandel
authors.affiliation: Department of Neurology, Besançon University Hospital, Besançon, France.|EA 481 Laboratory of Neurosciences, University of Franche-Comté, Besançon, France.
authors.forename: Eloi
authors.initials: E
authors.lastname: Magnin
authors.affiliation: Department of Neurology, Besançon University Hospital, Besançon, France.|Rapid-Fr network (Regional Network for Diagnostic Aid and Management of Patients with Cognitive Impairment - Department of Franche-Comté), Besançon, France.
authors.forename: Eric
authors.initials: E
authors.lastname: Berger
authors.affiliation: Department of Neurology, Besançon University Hospital, Besançon, France.|Rapid-Fr network (Regional Network for Diagnostic Aid and Management of Patients with Cognitive Impairment - Department of Franche-Comté), Besançon, France.
authors.forename: Jean
authors.initials: J
authors.lastname: Galmiche
authors.affiliation: Clinical Methodology Center, Besançon University Hospital, Besançon. France.|Chrono-environnement Laboratory, UMR6249 CNRS, University of Franche-Comté, Besançon, France.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Mauny
mesh_terms: D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D015982:Bias; D060825:Cognitive Dysfunction / Q000175:diagnosis* / Q000453:epidemiology*; D004522:Educational Status; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D012680:Sensitivity and Specificity
keywords: Amnestic mild cognitive impairment; screening; single cutoff; spectrum bias; spectrum effect