title: Use of reverse-transcriptase-based HIV-1 viral load assessment to confirm low viral loads in newly diagnosed patients in Switzerland.
abstract: BACKGROUND
  Treatment-naïve patients newly diagnosed with HIV occasionally present with low viral RNA of ≤1'000 copies/ml, raising concerns about viral load underestimation. Because falsely low or undetectable viral loads might lead to inadvertent virus transmission or treatment delays, confirmation of such cases by a sequence-independent viral load test is recommended in Switzerland.
  
  
  METHODS
  HIV-1 RNA ≤1'000 cp/ml by Roche's or Abbott's tests in patients newly diagnosed from 2010 to 2012 in Switzerland were subjected to viral load testing by the product-enhanced-reverse transcriptase (PERT) assay. These investigations were complemented with repeat and/or alternative viral RNA measurements.
  
  
  RESULTS
  HIV-1 RNA ≤1'000 cp/ml was observed in 71 of 1814 newly diagnosed patients. The PERT assay suggested clinically relevant viral load underestimation in 7 of 32 cases that could be investigated. In four patients, the PERT viral load was 10-1'000-fold higher; this was confirmed by alternative HIV-1 RNA tests. Six of the 7 underestimates had been obtained with meanwhile outdated versions of Roche's HIV-1 RNA test. In the seventh patient, follow-up revealed similar results for RNA and PERT based viral loads.
  
  
  CONCLUSIONS
  PERT assay revealed occasional severe viral load underestimation by versions of HIV-1 RNA tests meanwhile outdated. Underestimation by contemporary tests appears rare, however.
authors: Swiss National Center for Retroviruses, Institute of Medical Virology, University of Zurich, Zurich, Switzerland. vetter.beatrice@virology.uzh.ch.
authors: Beatrice N
authors: BN
authors: Vetter
authors: Cyril
authors: C
authors: Shah
authors: Jon B
authors: JB
authors: Huder
authors: Jürg
authors: J
authors: Böni
authors: Jörg
authors: J
authors: Schüpbach
mesh_terms: D012321:DNA-Directed RNA Polymerases; D015658:HIV Infections / Q000175:diagnosis*; D054303:HIV Reverse Transcriptase / Q000737:chemistry*; D015497:HIV-1; D006801:Humans; D012367:RNA, Viral / Q000032:analysis; D011933:Reagent Kits, Diagnostic; D013557:Switzerland; D019562:Viral Load
chemical_list: D012367:RNA, Viral; D011933:Reagent Kits, Diagnostic; C514824:reverse transcriptase, Human immunodeficiency virus 1; D054303:HIV Reverse Transcriptase; D012321:DNA-Directed RNA Polymerases