title: Development of a subjective cognitive decline questionnaire using item response theory: a pilot study.
abstract: BACKGROUND
  Subjective cognitive decline (SCD) may indicate unhealthy cognitive changes, but no standardized SCD measurement exists. This pilot study aims to identify reliable SCD questions.
  
  
  METHODS
  112 cognitively normal (NC, 76±8 years, 63% female), 43 mild cognitive impairment (MCI; 77±7 years, 51% female), and 33 diagnostically ambiguous participants (79±9 years, 58% female) were recruited from a research registry and completed 57 self-report SCD questions. Psychometric methods were used for item-reduction.
  
  
  RESULTS
  Factor analytic models assessed unidimensionality of the latent trait (SCD); 19 items were removed with extreme response distribution or trait-fit. Item response theory (IRT) provided information about question utility; 17 items with low information were dropped. Post-hoc simulation using computerized adaptive test (CAT) modeling selected the most commonly used items (n=9 of 21 items) that represented the latent trait well (r=0.94) and differentiated NC from MCI participants (F(1,146)=8.9, p=0.003).
  
  
  CONCLUSIONS
  Item response theory and computerized adaptive test modeling identified nine reliable SCD items. This pilot study is a first step toward refining SCD assessment in older adults. Replication of these findings and validation with Alzheimer's disease biomarkers will be an important next step for the creation of a SCD screener.
authors.affiliation: Vanderbilt Memory & Alzheimer's Center, Department of Neurology, Vanderbilt University Medical Center, Nashville, TN.
authors.forename: Katherine A
authors.initials: KA
authors.lastname: Gifford
authors.affiliation: Department of Biostatistics, Vanderbilt University School of Medicine, Nashville, TN.
authors.forename: Dandan
authors.initials: D
authors.lastname: Liu
authors.affiliation: Vanderbilt Memory & Alzheimer's Center, Department of Neurology, Vanderbilt University Medical Center, Nashville, TN.
authors.forename: Raymond
authors.initials: R
authors.lastname: Romano
authors.affiliation: Brown University Warren Alpert Medical School, Department of Psychiatry & Human Behavior, Providence, RI.
authors.forename: Richard N
authors.initials: RN
authors.lastname: Jones
authors.affiliation: Vanderbilt Memory & Alzheimer's Center, Department of Neurology, Vanderbilt University Medical Center, Nashville, TN.
authors.forename: Angela L
authors.initials: AL
authors.lastname: Jefferson
keywords: Subjective cognitive decline; computerized adaptive testing; factor analysis; item-response theory; mild cognitive impairment; psychometrics