HIV Window Period and Recommended HIV Test

April 06,2021
5 Min Read

Generation (Older Categorization)	New Categorization	Window period	Detects Antibody or Antigen (Ag)	Sensitivity	Specificity	Result
1st generation	IgG-sensitive tests	8-10 weeks	IgG Anti HIV-1	99%	95-99%	Single result
2nd generation	IgG-sensitive tests	4-6 weeks	IgG Anti HIV-1 & IgG Anti HIV-2	>99.5%	>99	Single result
3rd generation	IgM.IgG- sensitive tests	2-3 weeks	IgG and IgM anti HIV-1, HIV-2, and HIV Group-O	>99.5%	>99.5%	Single result
4th generation	Antigen/ Antibody Combination tests	2 weeks	IgG and IgM anti HIV-1, HIV-2, and HIV Group-O. Also detects HIV-1 p24 Ag	>99.8%	99.5%	Single result; does not differentiate Antibody from Antigen positivity
5th generation	Antigen/ Antibody Combination tests	2 weeks	IgG and IgM anti HIV-1, HIV-2, and HIV Group-O. Also detects HIV-1 p24 Ag	100%	99.5%	Separate HIV-1 and HIV-2 Antibody and Antigen results

*There is some controversy with calling these 5th generation tests, because there is no reduction of window period from the 4th generation. Reduction in the window period is what is usually differentiates 2 generations of tests.

References:

1. Alexander TS. Human Immunodeficiency Virus Diagnostic Testing: 30 Years of Evolution. Clin Vaccine Immunol. 2016 Apr 1;23(4):249-53.

2. Blog LBP. Best Practices for HIV-1/2 Screening: When to Test and What to Test [Internet]. Laboratory Best Practices Blog. [cited 2020 Nov 19]. Available from: https://blog.ucdmc.ucdavis.edu/labbestpractice/index.php/2017/09/15/best-practices-for-hiv-12-screening-when-to-test-and-what-to-test/

3. A “fifth generation” HIV assay? [Internet]. Medical Laboratory Observer. [cited 2020 Nov 19]. Available from: https://www.mlo-online.com/home/article/13008643/a-fifth-generation-hiv-assay

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