A multi-center study comparing the analytical sensitivity and clinical concordance of three HIV-1 viral load assays

Virological safety of the UK blood supply in the era of individual risk assessments and HIV PrEP

A more individualised donor selection policy was implemented in the UK in 2021, which replaced the previous 3-month deferral for men who have sex with men (MSM). Other blood services have a variety of policies in place to ensure the virological safety of blood components, ranging from an indefinite ban on MSM, to a defined period of exclusion, or to an individualised risk assessment that is not based on gender or sexual orientation. Justification of these policies should be based on scientific evidence including assessment of lengths of virological window periods, infectious disease epidemiology within donor populations and donation screening assay sensitivities. Developments in molecular technology and assays which can detect both antibodies and antigens in the very early stages of infection have significantly reduced the risk in most developed countries. However, the increasing usage of pre-exposure prophylaxis (PrEP) to prevent acquisition of HIV infection after possible high-risk sexual contact within the UK blood donor population has been recently noted. It has brought with it new diagnostic challenges within blood screening, notably possible non-detection of HIV RNA and serological markers following PrEP use despite potential infectivity. The use of other testing strategies such as detection of HIV DNA and screening for non-declared PrEP usage should be investigated further.

More HIV-1 RNA detected and quantified with the Cobas 6800 system in patients on antiretroviral therapy

BACKGROUND

Target-detected (TD) results or low-level viraemia (LLV) can be observed in HIV-1 patients on ART, which regularly raises questions.

OBJECTIVES

We describe here the impact on HIV-1 RNA quantification of switching from the COBAS AmpliPrep/COBAS TaqMan (CAP/CTM) to the Cobas 6800 system (C6800), based on analyses of viraemia close to the lower limit of quantification (LLoQ).

PATIENTS AND METHODS

We retrospectively selected two groups of patients: 200 individuals whose viral loads (VLs) were consistently <50 copies/mL with CAP/CTM for at least 3 years before switching to C6800 (group 1), and 35 other patients with confirmed LLV when C6800 was in use (group 2). In both groups, we compared several consecutive VL results performed before and after the change of quantification assay. Analyses were performed with McNemar's paired tests or Fisher's exact tests.

RESULTS

In group 1, the frequency of TD results (below or above the LLoQ) increased significantly after the switch to C6800 for patients with <25% of results being TD for VLs performed with CAP/CTM (P < 0.0001). Significantly more patients had at least one VL ≥20 or ≥50 copies/mL with C6800, in both group 1 (37.0% versus 18.5%; P < 0.0001 and 6.5% versus 0%; P = 0.0009, respectively) and group 2 (100% versus 66%; P = 0.0015 and 97% versus 40%; P < 0.0001, respectively).

CONCLUSIONS

C6800 revealed residual or low-level HIV-1 RNA that was not detected with CAP/CTM, resulting in twice as many patients being found to have a VL ≥20 copies/mL. Physicians and patients should be aware of possible differences in results between assays, and it is crucial to specify the quantitative assay used in studies.