Diagnosing human immunodeficiency virus 1 (HIV) infections relies on viral nucleic acid testing (NAT). Measurement of HIV viral load (VL) generally utilizes plasma samples.

The present study assessed and compared plasma HIV VL results with serum samples results to enable the use of serum in urgent contexts where plasma is unavailable. 

• It used the Alinity m assay system to test stored serum samples retrospectively for HIV VL and compared the findings to those obtained with plasma collected on the same day.
• The quantitative results showed a high correlation and were equivalent.
• The two sample types showed no significant differences.
• Additionally, they showed a qualitative correlation and few discordances among very low-titered samples; at low levels of viremia (<100 copies/ml), NATs are generally considered less accurate.
• Regarding quantitative results and considering the thresholds adopted by French guidelines, the study found a perfect correlation (100%), and equivalent HIV VL values on testing paired samples of plasma and serum with VL< 50 or > 400 cp/ml.

This study showed that the quantitative amplification of HIV-1 RNA in serum is possible, and the results are similar to those obtained in plasma. These findings will help when a plasma sample is unavailable in specific therapeutic emergencies, such as primary infection or managing the delivery of an HIV-positive pregnant woman. Adopting this approach could potentially reduce the delay in care, which will benefit not only patients and physicians but also workflows in the laboratory.

Mouna L, Pallier C, Proust S, Roque-Afonso A-M. Comparison of serum and plasma viral load measurements in human immunodeficiency virus type 1 infection. Journal of Clinical Virology Plus. 2022. https://doi.org/10.1016/j.jcvp.2022.100127.