Use of reverse-transcriptase-based HIV-1 viral load assessment to confirm low viral loads in newly diagnosed patients in Switzerland
Swiss National Center for Retroviruses, Institute of Medical Virology, University of Zurich, Zurich, Switzerland
BMC Infectious Diseases 2014, 14:84 doi:10.1186/1471-2334-14-84Published: 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 Six of the 7 underestimates had been obtained with meanwhile outdated versions of Roche’s HIV-1 RNA test.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PERT assay revealed occasional severe viral load underestimation by versions of HIV-1 RNA tests meanwhile outdated.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.