Open Access Highly Accessed Research article

Use of reverse-transcriptase-based HIV-1 viral load assessment to confirm low viral loads in newly diagnosed patients in Switzerland

Beatrice N Vetter*, Cyril Shah, Jon B Huder, Jürg Böni and Jörg Schüpbach

Author Affiliations

Swiss National Center for Retroviruses, Institute of Medical Virology, University of Zurich, Zurich, Switzerland

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BMC Infectious Diseases 2014, 14:84  doi:10.1186/1471-2334-14-84

Published: 13 February 2014



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.


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.


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 Six of the 7 underestimates had been obtained with meanwhile outdated versions of Roche’s HIV-1 RNA test.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.


PERT assay revealed occasional severe viral load underestimation by versions of HIV-1 RNA tests meanwhile outdated. Underestimation by contemporary tests appears rare, however.

HIV-1; Viral load underestimation; Nucleic acid test; Reverse transcriptase test; PERT assay