Fourth generation HIV rapid diagnostic test: Adequate sensitivity in HIV primary infection settings?

BACKGROUND

HIV rapid diagnostic tests (RDT) enable easy point-of-care screenings but traditionally lack the HIV-1 p24-antigen detection, resulting in poor diagnostic window, up to three months after exposure. Fourth-generation HIV RDTs aimed to address this issue, through independent detection of p24-antigen and HIV-antibodies, but their performances in primary infection settings remains understudied.

OBJECTIVE

To compare the sensitivity of two fourth-generation HIV RDTs, Determine™ Early Detect (Determine) and AQ+ HIV Ag/Ab Combo (AQ+), in primary HIV-1 infection samples.

METHODS

Sensitivity of Determine and AQ+ was assessed using 162 primary infection samples. Primary infection was determined using the New Lav blot I (Bio-Rad) Western blot, with pre-seroconversion defined by a p24-positivity with the absence of HIV-1 antibodies on the 4th generation enzyme immunoassay Liaison XL. HIV-1 infection dates were retrieved from medical records.

RESULTS

Overall sensitivity [95 % CI] was at 94.4 % [89.8-97.1 %] and 96.9 % [93.0-98.7 %] for Determine and AQ+ , respectively (p = 0.22). Pre-seroconversion sensitivity was at 66.7 % [47.8-81.3 %] and 81.5 % [63.3-91.8 %] for Determine and AQ+ , respectively (p = 0.22). All seroconversion samples were reactive on both assays. Regarding window periods, no assay was reactive the two first weeks after infection (n = 2), Between two and three weeks after infection (n = 11), sensitivity was at 73 % [43-90 %] and 91 % [62-98 %] for Determine and AQ+ , respectively. After three weeks (n = 26), all samples were reactive on both assays, with a 100 % [87-100 %] sensitivity.

CONCLUSION

Fourth-generation HIV RDT can be useful for a suspected primary HIV-1 infection, but should be used with caution the first three weeks post-infection.