title: Quantifying cognition at the bedside: a novel approach combining cognitive symptoms and signs in HIV.
abstract: BACKGROUND
  Up to half of all people with HIV infection have some degree of cognitive impairment. This impairment is typically mild, but nonetheless often disabling. Although early detection of cognitive impairment offers the greatest hope of effective intervention, there are important barriers to this goal in most clinical settings. These include uncertainty about how self-reported cognitive symptoms relate to objective impairments, and the paucity of bedside measurement tools suitable for mild deficits. Clinicians need guidance in interpreting cognitive symptoms in this population, and a brief cognitive measurement tool targeted to mild impairment. We addressed these two problems together here. The objective of this study was to determine the extent to which performance on cognitive tests and self-reported cognitive symptoms form a unidimensional construct.
  
  
  METHODS
  Two hundred three HIV+ individuals completed the Montreal Cognitive Assessment, computerized cognitive tasks and a questionnaire eliciting cognitive symptoms. Rasch measurement theory was applied to determine whether patient-reported and performance items could be combined to measure cognition as a unidimensional latent construct.
  
  
  RESULTS
  Performance-based items and cognitive symptoms are arranged hierarchically along the same continuum of cognitive ability, forming a measure with thresholds covering a broad spectrum of ability that has good internal reliability. The cognitive symptoms that fit the measurement model relate to important aspects of everyday life, providing evidence that the identified construct is meaningful.
  
  
  CONCLUSIONS
  This finding lays the foundation for a rapid measure of cognitive ability in people with HIV infection that is feasible for routine clinical use, and shows that some cognitive symptoms are systematically related to performance in this population.
authors.affiliation: Department of Psychiatry, Faculty of Medicine, McGill University, Montreal, QC, Canada. marie-josee.brouillette@mcgill.ca.|Chronic Viral Illness Service, McGill University Health Center, Montreal, QC, Canada. marie-josee.brouillette@mcgill.ca.|Research Institute of the McGill University Health Centre, Montreal, QC, Canada. marie-josee.brouillette@mcgill.ca.|McGill University Health Centre, Glen site, 1001 Decarie, D02.4110, Montreal, QC, H4A 3J1, Canada. marie-josee.brouillette@mcgill.ca.
authors.forename: Marie-Josée
authors.initials: MJ
authors.lastname: Brouillette
authors.affiliation: Department of Neurology and Neurosurgery, Faculty of Medicine, McGill University, Montreal, QC, Canada. lesley.fellows@mcgill.ca.|Montreal Neurological Institute, McGill University, Montreal, QC, Canada. lesley.fellows@mcgill.ca.
authors.forename: Lesley K
authors.initials: LK
authors.lastname: Fellows
authors.affiliation: School of Physical and Occupational Therapy, Faculty of Medicine, McGill University, Montreal, QC, Canada. lisa.palladini@mail.mcgill.ca.
authors.forename: Lisa
authors.initials: L
authors.lastname: Palladini
authors.affiliation: Division of Clinical Epidemiology, McGill University Health Center, Montreal, QC, Canada. lois.finch@mail.mcgill.ca.
authors.forename: Lois
authors.initials: L
authors.lastname: Finch
authors.affiliation: Clinique Médicale l'Actuel, Montreal, QC, Canada. rejean.thomas@lactuel.ca.
authors.forename: Réjean
authors.initials: R
authors.lastname: Thomas
authors.affiliation: School of Physical and Occupational Therapy, Faculty of Medicine, McGill University, Montreal, QC, Canada. nancy.mayo@mcgill.ca.|Division of Clinical Epidemiology, McGill University Health Center, Montreal, QC, Canada. nancy.mayo@mcgill.ca.
authors.forename: Nancy E
authors.initials: NE
authors.lastname: Mayo
mesh_terms: D000328:Adult; D001288:Attention / Q000502:physiology; D003071:Cognition / Q000502:physiology*; D003072:Cognition Disorders / Q000175:diagnosis*; D003863:Depression / Q000523:psychology; D004522:Educational Status; D056344:Executive Function / Q000502:physiology; D005240:Feasibility Studies; D005260:Female; D015658:HIV Infections / Q000523:psychology*; D006679:HIV Seropositivity / Q000523:psychology; D006801:Humans; D008297:Male; D008568:Memory / Q000502:physiology; D008875:Middle Aged; D019095:Point-of-Care Systems; D015203:Reproducibility of Results; D057566:Self Report; D011795:Surveys and Questionnaires; D019562:Viral Load / Q000145:classification