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. When impairment was defined as < -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. Conclusion: 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. Trial registration: EUDRACT: 2007-006448-23 and ISRCTN04857074. © 2014 Arenas-Pinto et al.