The Relationship Between Self-reported Adherence and Efavirenz Blood Levels on the Appearance of HIV Viral Load Blips
Intermittent episodes of low-level viremia, termed “blips”, can sometimes occur in HIV-infected persons on viral load (VL)-suppressive antiretroviral therapy (ART). The underlying causes of blips are not completely understood. We evaluated the association between self-reported adherence (SRA) and plasma drug levels in the U.S. Military HIV Natural History Study.
Participants experiencing blips on their initial single tablet ART regimen of efavirenz/emtricitabine/tenofovir (EFV/FTC/TDF) with available SRA data and repository plasma specimens on consecutive blip and non-blip dates were included. Blips were defined as a plasma VL ≥50 copies/mL, with values <50 copies/mL before and after the blip timepoint. SRA was categorized as < or ≥85% and assessed at both the blip and non-blip timepoints. Untimed plasma levels were measured for the EFV component of the regimen by high-performance liquid chromatography (HPLC) for the corresponding blip and non-blip timepoints. Random EFV levels below reported minimum trough concentration of 1 mcg/mL were considered subtherapeutic. SRA and EFV plasma levels were analyzed as categorical values < or ≥85% and above or below therapeutic threshold, respectively, by Chi-square test.
A total of 116 participants met inclusion criteria. SRA was <85% for 6 of 232 (2.6%) timepoints, including 3 of 116 (2.6%) blip timepoints and 3 of 116 (2.6%) non-blip timepoints. Of the 232 specimens analyzed, 12 (5.2%) had EFV levels below threshold, including 5 of 116 (4.3%) blip and 7 of 116 (6.0%) non-blip timepoints. Among those with subtherapeutic EFV levels, adherence ≥85% was self-reported by 4 of 5 (80%) and 7 of 7 (100%) participants on blip and non-blip dates, respectively. There was no statistically significant association between SRA and EFV levels at either blip (P=0.12) or non-blip (P=0.11) timepoints.
The vast majority of participants experiencing blips had SRA ≥85%. Although studies have shown that suboptimal adherence results in reduced drug levels, we observed no association between SRA and untimed EFV levels in this retrospective study. This suggests that other factors, such as viral replication from reservoirs or VL assay variability, may be responsible for blip episodes.
A. Ganesan, None
R. Deiss, None
B. Agan, None
K. S. Akers, None
J. Okulicz, None
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