HIV Window Period and Recommended HIV Test
| 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 | 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 | 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:
- Alexander TS. Human Immunodeficiency Virus Diagnostic Testing: 30 Years of Evolution. Clin Vaccine Immunol. 2016 Apr 1;23(4):249-53.
- 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/
- 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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