title: Neurocognitive function in HIV-infected patients: comparison of two methods to define impairment.
abstract: OBJECTIVE
  To compare two definitions of neurocognitive impairment (NCI) in a large clinical trial of effectively-treated HIV-infected adults at baseline.
  
  
  METHODS
  Hopkins Verbal Learning test-Revised (HVLT-R), Colour Trail (CTT) and Grooved Pegboard (GPT) tests were applied exploring five cognitive domains. Raw scores were transformed into Z-scores and NCI defined as summary NPZ-5 score one standard deviation below the mean of the normative dataset (i.e. <-1SD) or Z-scores <-1SD in at least two individual domains (categorical scale). Principal component analysis (PCA) was performed to explore the contribution of individual tests to the total variance.
  
  
  RESULTS
  Mean NPZ-5 score was -0.72 (SD 0.98) and 178/548 (32%) participants had NPZ-5 scores <-1SD. When impairment was defined as <-1SD in at least two individual tests, 283 (52%) patients were impaired. Strong correlations between the two components of the HVLT-R test (learning/recall) (r = 0.73), and the CTT and (attention/executive functioning) (r = 0.66) were observed. PCA showed a clustering with three components accounting for 88% of the total variance. When patients who scored <-1SD only in two correlated tests were considered as not impaired, prevalence of NCI was 43%. When correlated test scores were averaged, 36% of participants had NPZ-3 scores <-1SD and 32% underperformed in at least two individual tests.
  
  
  CONCLUSIONS
  Controlling for differential contribution of individual test-scores on the overall performance and the level of correlation between components of the test battery used appear to be important when testing cognitive function. These two factors are likely to affect both summary scores and categorical scales in defining cognitive impairment.
  
  
  BACKGROUND
  EUDRACT: 2007-006448-23 and ISRCTN04857074.
authors: MRC Clinical Trials Unit at UCL, Institute of Clinical Trials and Methodology, London, United Kingdom; Centre for Sexual Health and HIV Research, University College London, London, United Kingdom.
authors: Alejandro
authors: A
authors: Arenas-Pinto
authors: Section of Infectious Diseases, Division of Medicine, Imperial College, St Mary's Hospital Campus, London, United Kingdom; Department of HIV and GU Medicine, Imperial College Healthcare NHS Trust, London, United Kingdom.
authors: Alan
authors: A
authors: Winston
authors: MRC Clinical Trials Unit at UCL, Institute of Clinical Trials and Methodology, London, United Kingdom.
authors: Wolfgang
authors: W
authors: Stöhr
authors: Infectious Diseases, Southend University Hospital NHS Foundation Trust, Westcliff-on-Sea, United Kingdom.
authors: John
authors: J
authors: Day
authors: Centre for Immunology and Infection, Department of Biology, University of York, York, United Kingdom.
authors: Rebecca
authors: R
authors: Wiggins
authors: Department of GU Medicine, Royal Victoria Hospital, Belfast, United Kingdom.
authors: Say Pheng
authors: SP
authors: Quah
authors: Infectious Diseases, North Middlesex University Hospital, London, United Kingdom.
authors: Jonathan
authors: J
authors: Ainsworth
authors: MRC Clinical Trials Unit at UCL, Institute of Clinical Trials and Methodology, London, United Kingdom.
authors: Sue
authors: S
authors: Fleck
authors: MRC Clinical Trials Unit at UCL, Institute of Clinical Trials and Methodology, London, United Kingdom.
authors: David
authors: D
authors: Dunn
authors: Psychology and Psychotherapy Department, The Mortimer Market Centre, Central and North West London NHS Foundation Trust, London, United Kingdom.
authors: Alex
authors: A
authors: Accoroni
authors: MRC Clinical Trials Unit at UCL, Institute of Clinical Trials and Methodology, London, United Kingdom; Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
authors: Nicholas I
authors: NI
authors: Paton
mesh_terms: D000328:Adult; D003072:Cognition Disorders / Q000209:etiology / Q000503:physiopathology*; D005260:Female; D015658:HIV Infections / Q000150:complications / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D025341:Principal Component Analysis