SPP1 and asymptomatic neurocognitive impairment: OPN levels were highest in the HIV+ ANI cases (1.706 ± 1.045, n = 6) compared to all other groups (normal, 1.394 ± 0.748, p = 0.005, n = 10; HIV+ MND/HAD, 1.428 ± 0.589, p = 0.023, n = 8; ALS, 1.226 ± 0.862, p < 0.0001, n = 5) (Fig. 7).