Background: Despite modern antiretroviral therapy, human immunode�ciency virus-1 (HIV-1) ribonucleic acid (RNA) escape into the cerebrospinal fluid (CSF) may occur. We examined the prevalence of and factors associated with CSF HIV-1 escape among people living with HIV (PLWH) in Switzerland.
Setting: The Neurocognitive Assessment in the Metabolic and Aging Cohort study is an ongoing, prospective, longitudinal, multicenter study within the Swiss HIV Cohort Study. The neuro- HIV platform is a multidisciplinary, single-day outpatient consulta- tion at Lausanne University Hospital.
Methods: We pooled data from the Neurocognitive Assessment in the Metabolic and Aging Cohort study and the neuro-HIV platform participants who underwent lumbar puncture between 2011 and 2019. Both patient groups had neurocognitive symptoms. Cerebrospinal fluid HIV-1 escape was de�ned as the presence of quanti�able CSF HIV-1 RNA when plasma HIV-1 RNA was suppressed or CSF HIV-1 RNA greater than plasma HIV-1 RNA when the latter was detectable.

Results: Of 1166 PLWH assessed, 288 underwent lumbar puncture. Cerebrospinal fluid HIV-1 escape was observed in 25 PLWH (8.7%) of whom 19 (76%) had suppressed plasma HIV-1 RNA. Character- istics of PLWH were comparable whether they had CSF HIV-1 escape or not, including comorbidities, time since HIV diagnosis (15 vs 16 years, P = 0.9), median CD4 nadir (158.5/mm3 vs 171/mm3, P = 0.6), antiretroviral CSF penetration-effectiveness score (7 vs 7 points, P = 0.8), and neurocognitive diagnosis based on Frascati criteria and radiological �ndings.
Conclusions: In this large pooled sample of PLWH with neuro- cognitive symptoms, CSF HIV-1 escape occurred in 8.7% of PLWH. People living with HIV with CSF HIV-1 escape presented no distinctive clinical or paraclinical characteristics. We conclude that lumbar puncture is unavoidable in con�rming CSF HIV-1 escape.