24 Nov Too stringent viral load thresholds?
Viral load (VL) monitoring is being rapidly scaled up in resource-limited settings to help meet the UNAIDS 90-90-90 treatment goal of 73% viral suppression among all people living with HIV (PLHIV). Dried blood spots (DBS) make VL testing available to peripheral sites, however they have a lower amplification sensitivity and may over-estimate VL due to co-amplification of cell-associated viruses. WHO recently revised the virological failure (VF) threshold down to 1,000cps/ml. Seth Inzaule cs used routine data from western Kenya and five commonly used assays to assess whether the previous threshold (3,000-5,000cps/ml) or the new threshold led to more unnecessary repeat tests or regimen switches and/or less detection of VF. Changing the threshold from 5,000 to 1,000cps/ml would result in 2-9 additional repeat tests and 2-6 additional switches per 100 VL tests. Conversely, the proportion of patients potentially maintained on a failing regimen due to undetected VF was between 0 (Abbott) and 3.9% (Roche CAP/CTM) at 1,000cps/ml and 0 (Abbott) and 2.7% (NucliSENS) at 5,000cps/ml. The more stringent VF threshold would result in substantial increases in unnecessary VL repeat tests and treatment switches, with important resource implications. Until improved DBS-based technologies are available, a more practical threshold seems sensible.
Authors: Seth Inzaule MSc, Raph Hamers MD PhD, Clement Zeh PhD, Tobias F. Rinke de Wit PhD in JAIDS 2015.