The variable sensitivity of HIV Ag/Ab combination assays in the detection of p24Ag according to genotype could compromise the diagnosis of early HIV infection.
BACKGROUND
In France, HIV infection diagnosis was modified by a decree, published in 2010, that requires the use of HIV Ag/Ab assays able to detect at least 2 IU/ml of p24Ag. This measure raises the concern of the capacity of these assays to equally detect all HIV variants.


OBJECTIVE
To assess the performance of HIV Ag/Ab assays for the detection of p24Ag from diverse HIV isolates.


METHODS
Ten HIV Ag/Ab assays were compared using two p24Ag reference standards, 297 samples from 99 HIV-1 and HIV-2 cell-culture derived isolates including various subtypes and groups, and 9 native specimens from subjects with primary HIV infection.


RESULTS
The p24Ag limit of detection (LOD) ranged from 0.505 IU/ml to 1.90 1 IU/ml and, from 11.9 pg/ml to 33.5 pg/ml when using WHO and French national standards, respectively. The overall percentage of positive samples ranged from 26.8% to 74.5%. Five assays failed to detect all dilutions of at least one group M subtype, three missed all group O and six all the group P samples. Three assays were able to detect 2-10 of the 30 HIV-2 samples. The distribution of LODs for each group M isolate showed a wide dispersion between the assays. Percentage of isolates detected at a p24Ag level less than 2 IU/ml varied from 22% to 98.7%.


CONCLUSIONS
This study demonstrated that, even though their analytical sensitivity fulfills the requirements, many of HIV Ag/Ab assays could fail to detect HIV primary infection due to HIV-1 non-B, non-M and HIV-2 strains.
Biomnis Laboratory, Ivry sur Seine, France.
Thoai Duong
TD
Ly
Jean Christophe
JC
Plantier
Lionel
L
Leballais
Sylvie
S
Gonzalo
Véronique
V
Lemée
Syria
S
Laperche
D005602:France; D005838:Genotype; D015483:HIV Antibodies / Q000097:blood*; D016655:HIV Core Protein p24 / Q000097:blood*; D015658:HIV Infections / Q000175:diagnosis* / Q000821:virology*; D015497:HIV-1 / Q000145:classification / Q000235:genetics / Q000276:immunology*; D015498:HIV-2 / Q000145:classification / Q000235:genetics / Q000276:immunology*; D012680:Sensitivity and Specificity
D015483:HIV Antibodies; D016655:HIV Core Protein p24