Factors Associated with Low-Level Viraemia and Virological Failure: Results from the Austrian HIV Cohort Study

PLoS One. 2015 Nov 13;10(11):e0142923. doi: 10.1371/journal.pone.0142923. eCollection 2015.


Background: In human immunodeficiency virus treatment adequate virological suppression is warranted, nevertheless for some patients it remains a challenge. We investigated factors associated with low-level viraemia (LLV) and virological failure (VF) under combined antiretroviral therapy (cART).

Materials and methods: We analysed patients receiving standard regimens between 1st July 2012 and 1st July 2013 with at least one viral load (VL) measurement below the quantification limit (BLQ) in their treatment history. After a minimum of 6 months of unmodified cART, the next single VL measurement within 6 months was analysed. VF was defined as HIV RNA levels ≥ 200 copies/mL and all other quantifiable measurements were classified as LLV. Factors associated with LLV and VF compared to BLQ were identified by logistic regression models.

Results: Of 2276 participants, 1972 (86.6%) were BLQ, 222 (9.8%) showed LLV and 82 (3.6%) had VF. A higher risk for LLV and VF was shown in patients with cART interruptions and in patients with boosted PI therapy. The risk for LLV and VF was lower in patients from centres using the Abbott compared to the Roche assay to measure VL. A higher risk for LLV but not for VF was found in patients with a higher VL before cART [for >99.999 copies/mL: aOR (95% CI): 4.19 (2.07-8.49); for 10.000-99.999 copies/mL: aOR (95% CI): 2.52 (1.23-5.19)] and shorter cART duration [for <9 months: aOR (95% CI): 2.59 (1.38-4.86)]. A higher risk for VF but not for LLV was found in younger patients [for <30 years: aOR (95% CI): 2.76 (1.03-7.35); for 30-50 years: aOR (95% CI): 2.70 (1.26-5.79)], people originating from high prevalence countries [aOR (95% CI): 2.20 (1.09-4.42)] and in male injecting drug users [aOR (95% CI): 2.72 (1.38-5.34)].

Conclusions: For both VF and LLV, factors associated with adherence play a prominent role. Furthermore, performance characteristics of the diagnostic assay used for VL quantification should also be taken into consideration.

Publication types

  • Multicenter Study
  • Observational Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Anti-HIV Agents / therapeutic use
  • Anti-Retroviral Agents / therapeutic use
  • Austria
  • Female
  • HIV Infections / drug therapy*
  • HIV Infections / virology*
  • HIV-1
  • Humans
  • Logistic Models
  • Male
  • Medication Adherence
  • Middle Aged
  • Multivariate Analysis
  • Prospective Studies
  • RNA, Viral / blood
  • Retrospective Studies
  • Risk Factors
  • Substance Abuse, Intravenous
  • Treatment Failure
  • Viral Load
  • Viremia / virology


  • Anti-HIV Agents
  • Anti-Retroviral Agents
  • RNA, Viral

Grants and funding

This work was supported by the Austrian Agency for Health and Food Safety (AGES). The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.