Table 1.

Methods applied to discriminate between recent and long-standing HIV infections.

Assay	Basis & interpretation & assay type	Technique*	Test	Reference
Serological assays
Detuned	Anti-HIV antibody titer is rising gradually after seroconversion.	First generation EIA	Abbott HIV-1 3A11, Abbott Laboratories**	[15]
			Vironostika HIV-1 Microelisa, bioMerieux**	[30]
			Avioq HIV-1 Microelisa system, Avioq Inc.
	Results of a standard HIV diagnostic assay with a reduced sensitivity are below the specified cut-off value for recently HIV-infected individuals, and above this level for long-term infected subjects.	Rapid immunoassays	Determine HIV-1/2 assay, Abbott Laboratories	[32,33]
			OraQuick Advance HIV-1/2 assay, OraSure Technologies, Inc.	[33]
			Uni-Gold Recombigen, Trinity Biotech	[34]
	Modified commercial assay	Particle agglutination	HIV-1/2 particle agglutination test, Serodia	[35]
Avidity index	Anti-HIV antibody avidity is increasing gradually after seroconversion. Sample diluted with a dissociative agent and separately with a neutral substance is subjected to the standard HIV diagnostic test, and the avidity index (AI) is calculated. AI is below the specified cut-off in samples with low-avidity early antibodies from recently HIV-infected individuals, and above this level in samples with high-avidity mature antibodies from long-term infected subjects. Modified commercial assay	Third generation EIA	HIV-1/2 gO EIA for the AxSYM analyzer, Abbott Diagnosics	[20,41]
			Anti-HIV-1/2 Vitros ECi assay, Ortho-Clinical Diagnostics	[43]
			Genetic Systems HIV-1/2 Peptide EIA, BioRad Laboratories	[38]
BED EIA	Proportion of HIV specific IgG to total IgG is rising gradually after seroconversion. Results of a quantitative IgG-capture enzyme immunoassay are below the specified cut-off value for recently HIV-infected individuals, and above this level for long-term infected subjects. Commercial assay	Capture EIA	BED EIA HIV-1 Incidence Test, Calypte Biomedical Corporation	[19]
IDE-V3	Antibody response to the HIV-1 gp41 immunodominant epitope (IDE) and gp120-V3 loop is increasing after seroconversion***. Probability of a non-recent HIV infection is calculated from the reactivity of the specimen with the IDE and V3 in the enzyme immunoassay. In-house assay	EIA	IDE-V3 assay	[17]
Anti-p24 IgG3	IgG3 isotype antibodies are present early in the infection and are not detectable after about 4 months post-infection. Results of an isotype-specific enzyme immunoassay or Luminex-based assay are above the specified cut-off value for recently HIV-infected individuals, and below this level for long-term infected subjects. In-house assays	EIA	Anti-p24 IgG3 assay	[21]
		Luminex-based assay	Bio-Plex System, BioRad Laboratories	[61]
INNO-LIA	Anti-HIV antibody titer is rising gradually after seroconversion, and different anti-HIV antibodies emerge at different time post-seroconversion. HIV recency information is extracted from the Western Blot confirmatory test by applying the modified interpretation algorithms taking into account intensity of the antibody-antigen band and the specific banding pattern. Commercial assay, modified interpretation algorithms	Western Blot	INNO-LIA HIV-1/2 Score, Innogenetics	[18]
Viral marker-based assay
High-resolution melting	HIV genetic diversity is rising with the progress of infection. Viral genes are amplified and subjected to the LightScaner analysis to receive high-resolution melting scores. Low melting scores are associated with low viral genetic diversity and indicate recent HIV infection, whereas high melting scores are associated with high viral genetic diversity related to chronic HIV infection. In-house assay			[22]

^*EIA – enzyme immunoassay;

^**assays currently not produced or produced under a new name by another manufacturer;

^***gp – glycoprotein.