title: Is it time to rethink how neuropsychological tests are used to diagnose mild forms of HIV-associated neurocognitive disorders? Impact of false-positive rates on prevalence and power.
abstract: BACKGROUND
  Between 0 and 48% of normal HIV-uninfected individuals score below threshold neuropsychological test scores for HIV-associated neurocognitive disorders (HAND) or are false positives. There has been little effort to understand the effect of varied interpretations of research criteria for HAND on false-positive frequencies, prevalence and analytic estimates.
  
  
  METHODS
  The proportion of normal individuals scoring below Z score thresholds drawn from research criteria for HAND, or false-positive frequencies, was estimated in a normal Kenyan population and a simulated normal population using varied interpretations of research criteria for HAND. We calculated the impact of false-positive frequencies on prevalence estimates and statistical power.
  
  
  RESULTS
  False-positive frequencies of 2-74% were observed for asymptomatic neurocognitive impairment/mild neurocognitive disorder and 0-8% for HIV-associated dementia. False-positive frequencies depended on the definition of an abnormal cognitive domain, Z score thresholds and neuropsychological battery size. Misclassification led to clinically important overestimation of prevalence and dramatic decreases in power.
  
  
  CONCLUSIONS
  Minimizing false-positive frequencies is critical to decrease bias in prevalence estimates and minimize reductions in power in studies of association, particularly for mild forms of HAND. We recommend changing the Z score threshold to ≤-1.5 for mild impairment, limiting analysis to 3-5 cognitive domains and using the average Z score to define an abnormal domain.
authors.affiliation: Department of Neurology, San Francisco General Hospital, University of California, San Francisco, San Francisco, Calif., USA.
authors.forename: Ana-Claire L
authors.initials: AC
authors.lastname: Meyer
authors.forename: W John
authors.initials: WJ
authors.lastname: Boscardin
authors.forename: Judith K
authors.initials: JK
authors.lastname: Kwasa
authors.forename: Richard W
authors.initials: RW
authors.lastname: Price
mesh_terms: D003072:Cognition Disorders / Q000175:diagnosis* / Q000209:etiology / Q000523:psychology; D005189:False Positive Reactions; D015658:HIV Infections / Q000150:complications*; D006801:Humans; D009483:Neuropsychological Tests