Background:  Nadir CD4 cell count has been proposed as a new potential risk factor for irreversible HIV-related neurocognitive impairment. Furthermore, benefits of HAART have been observed to be insufficient for neurocognitive reversal. We compared different nadir CD4 cell count cutoffs to study their possible clinical significance related to the initiation of HAART.

Methods:  A total of 64 patients were included in this observational, cross-sectional study. Demographic, medical, and neurocognitive variables were assessed. We excluded patients who reported drug abuse, psychiatric treatment, or neurological disorders. The percentages of patients showing neurocognitive impairment were compared through different CD4 cell count cutoffs, significant for HAART initiation:  200, 250, 300, and 350 cells/mL. Neurocognitive and motor functions were also compared among these study groups. ANOVA, non-parametric, and χ² tests were developed.

Results:  The percentages of patients showing neurocognitive impairment were:  nadir ≤200 cutoff vs nadir >200 cutoff —73.1% vs 52.6%, respectively; nadir ≤250 vs nadir >250—66.7% vs 53.3%; nadir ≤300 vs nadir >300—63.9% vs 56.5%; nadir ≤350 vs nadir >350—57.1% vs 62.5%. Although differences did not reach statistical significance, the percentage of impaired patients tended to be higher while the nadir cutoff fell. Supporting these data, when neurocognitive functions were compared, statistical differences were found in 2 areas with respect to the nadir 200 cutoff:  attention/working memory (span backward, p = 0.032); and executive functions (TMT-B, p = 0.020). The functioning was better in the group with >200 cells/mL. By contrast, when functions were studied regarding the other nadir cutoffs, non-significant differences were found in any function. We observed a general tendency to present a more protected neurocognitive functioning in the groups of patients with nadir >200, >250, >300, and >350 cells/mL, as indicated by higher scores in most areas assessed in each group.

Conclusions:  Our results confirm that the nadir CD4 cell count is a potential risk factor for HIV-related neurocognitive impairment. The prevalence of neurocognitive impairment is higher in those patients with lower nadir counts but, in addition, relevant differences are found when neurocognitive functioning is studied considering the nadir CD4 value. Earlier initiation of HAART therapy is recommended to achieve the major neurocognitive protection.