Kalayjian RC, et al. - Researchers examined how plasma cystatin C is correlated with neurocognitive impairment (NCI). Before and during initial antiretroviral therapy (ART), they also investigated its value as a diagnostic marker. In participants of a 48-week randomized clinical trial of initial ART, they undertook multivariable logistic regression and generalized estimating equations examining correlations with NCI, determined by neuropsychological measurements. In models that excluded baseline measurements, a significant association of higher plasma cystatin C levels with NCI was observed. However, these levels seemed to have no utility as a diagnostic marker for this condition.