The current study explored the predictive validity of the Global Deficit Score (GDS) approach in summarizing neuropsychological (NP) test results, and specifically in detecting HIV-associated cognitive impairment. A comprehensive NP test battery was administered to 88 HIV+ subjects and 61 healthy HIV- controls comparable for age, education, and ethnicity. Demographically corrected test data were converted to a GDS, which simulates clinicians' ratings by quantifying the number and degree of impaired performances throughout the test battery while attaching relatively less significance to superior performances and/or those within normal limits. Our results indicated that the GDS approach effectively discriminated HIV+ and normal control groups, and accurately classified HIV+ individuals with NP impairment based on the "gold standard" clinical rating approach. Consistent with previous studies using different subject samples and different NP test batteries, the GDS cutpoint of >or=0.50 yielded optimal balance between sensitivity and specificity in classifying NP impairment, thus supporting the generalizability of the method. Moreover, the ability of the GDS to predict NP impairment across several cutpoints was quite strong, with positive predictive power values ranging from 0.71 to 1.00. These findings support the validity of the GDS as a clinically useful way of summarizing results on NP testing.

Both HIV infection and methamphetamine dependence can be associated with brain dysfunction. Little is known, however, about the cognitive effects of concurrent HIV infection and methamphetamine dependence. The present study included 200 participants in 4 groups: HIV infected/methamphetamine dependent (HIV+/METH+), HIV negative/methamphetamine dependent (HIV-/METH+), HIV infected/methamphetamine nondependent (HIV+/METH-), and HIV negative/methamphetamine nondependent (HIV-/METH-). Study groups were comparable for age, education, and ethnicity, although the HIV-/METH- group had significantly more females. A comprehensive, demographically corrected neuropsychological battery was administered yielding a global performance score and scores for seven neurobehavioral domains. Rates of neuropsychological impairment were determined by cutoff scores derived from performances of a separate control group and validated with larger samples of HIV+ and HIV- participants from an independent cohort. Rates of global neuropsychological impairment were higher in the HIV+/METH+ (58%), HIV-/METH+ (40%) and HIV+/METH- (38%) groups compared to the HIV-/METH- (18%) group. Nonparametric analyses revealed a significant monotonic trend for global cognitive status across groups, with least impairment in the control group and highest prevalence of impairment in the group with concurrent HIV infection and methamphetamine dependence. The results indicate that HIV infection and methamphetamine dependence are each associated with neuropsychological deficits, and suggest that these factors in combination are associated with additive deleterious cognitive effects. This additivity may reflect common pathways to neural injury involving both cytotoxic and apoptotic mechanisms.