Diagnosing Acute HIV Infection — Does Fourth-Generation Immunoassay Suffice?

Charles B. Hicks, MD reviewing De Souza MS et al. AIDS 2015 Apr 24.

In a population with high HIV prevalence, pooled nucleic acid testing of samples testing negative by fourth-generation HIV immunoassay increased AHI diagnosis by 38%.

Diagnosing acute HIV infection (AHI) is important because of the higher transmission risk during this period and the potential for early treatment to limit the HIV reservoir. Improvements in HIV testing have led to the current, fourth-generation (4thG) antigen/antibody immunoassay, which has shortened the “window period” between HIV acquisition and diagnostic-test positivity by improving the sensitivity of the antibody test and incorporating p24 antigen detection to identify early, antibody-negative infection. To further improve AHI diagnosis, some advocate pooled HIV RNA screening (nucleic-acid testing [NAT]) of negative 4thG test samples.

The Thai Red Cross AIDS Research Centre in Bangkok tested 74,334 clients by 4thG immunoassay between June 2009 and February 2014; 8129 (10.9%) were HIV-positive, including 81 with AHI. Pooled NAT screening of 4thG immunoassay–negative samples identified an additional 31 cases of AHI. Compared with infections identified by 4thG testing, those detected by NAT were characterized by a significantly higher median CD4-cell count, a lower median HIV RNA viral load, and a shorter time from HIV exposure. The 38% increase in AHI diagnosis increased the number of AHI cases detected from 12 to 17 per 10,000 samples screened.

CITATION(S):

De Souza MS et al. Impact of nucleic acid testing relative to antigen/antibody combination immunoassay on the detection of acute HIV infection. AIDS 2015 Apr 24; 29:793.