Intraindividual variability in neurocognitive performance: No influence due to HIV status or self-reported effort

HIV-associated neurocognitive disorders (HAND) are estimated to affect approximately 50% of infected individuals at any one time. Dispersion, a type of intraindividual variability in neurocognitive test performance, has been identified as a potential behavioral marker of HAND; however, the specificity of dispersion to HAND and how it is influenced by participant effort when taking neurocognitive tests remain unclear.

Data were analyzed from 996 (474 HIV-, 522 HIV+) men enrolled in the Multicenter AIDS Cohort Study (MACS). Dispersion was calculated based on the standard deviation of an individual's test scores within a single assessment. Effort was determined using the Visual Analogue Effort Scale. Predictors of dispersion were determined using stepwise linear regression. Dispersion was compared between the HIV serostatus groups using analysis of covariance (ANCOVA), considering demographic and psychosocial variables that differed between the groups.

Contrary to our hypothesis, dispersion was not influenced by effort. Instead, poorer neurocognitive ability and race were the sole predictors of dispersion. Dispersion did not differ between the serostatus groups.

Our results indicate that dispersion is a valid indicator of neurocognitive dysfunction that is not due to suboptimal effort; however, it is not specific to HIV and is therefore of limited utility as a behavioral marker of HIV-related neurocognitive impairment.