mental health AIDS

Winter 2005 Newsletter / Volume 6, Issue 2

HIV Assessment News

Neuropsychological Assessment

In an effort to form and validate a screening battery for purposes of detecting HIV-related neuropsychological (NP) impairment, Carey et al. (2004b) compared the diagnostic accuracy of 14 paired combinations of six NP measures drawn from a larger NP battery administered to 190 people living with HIV. Performance was considered

NP impaired if demographically corrected T-scores fell below 40 on both tests, or below 35 on one test. ... The most sensitive test combinations were the Hopkins Verbal Learning Test - Revised (HVLT-R; Total Recall) and the Grooved Pegboard Test nondominant hand (PND) pair and the HVLT-R and WAIS-III Digit Symbol (DS) subtest pair (sensitivity = 78% and 75%, respectively). Both test combinations (HVLT-R/PND, HVLT-R/DS) were more accurate than the HIV Dementia Scale (HDS) in classifying HIV+ participants as NP impaired or unimpaired. (p. 234)

Carey and colleagues "suggest that demographically corrected T-scores from pairs of common NP measures may serve as valid screening instruments to identify subjects with HIV-related neurocognitive impairment who could benefit from more extensive NP examination" (p. 234).

In another study, Carey et al. (2004a) administered comprehensive NP test batteries to 88 HIV-positive individuals and 61 matched HIV-negative controls and converted demographically corrected test data to a Global Deficit Score (GDS). The GDS is a summary score that "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" (p. 307). They found that "the GDS discriminated between the HIV+ and HIV- groups such that the HIV+ sample's mean GDS was significantly higher (indicating poorer performance) than the HIV- sample. In fact, when examining the magnitude of between-group differences in performance, the GDS showed a larger effect size ... than any individual NP test ... . At a cutpoint of > 0.50, the ... clinician can be increasingly confident that HIV+ participants rather than healthy controls produced GDS scores in this range" (p. 314). Carey and colleagues conclude that the GDS is a clinically useful method of summarizing NP testing results, as their study

demonstrated the strong predictive power of the GDS method in classifying HIV group membership and HIV-associated NP impairment. The current findings also suggest that the GDS approach is generalizable to different NP test batteries comprised of demographically corrected measures that cover the same cognitive ability areas. By reporting several indices of diagnostic usefulness across a number of different cutpoints, we provided detailed information regarding the predictive validity of the GDS. Based on the approach's robust diagnostic efficiency across different samples and test batteries, coupled with its apparent ability to reduce both Type I [false positive] and Type II [false negative] error, we recommend the GDS approach as a valid and useful adjunct to statistically examining group mean differences. Our findings indicate that a GDS cutpoint of > 0.50 provided an optimal balance between sensitivity and specificity in the HIV+ sample ... . (p. 316)

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