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HIV Tests

  • April 06,2021
  • 5 Min Read
HIV Tests


 

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:

1. National Guidelines for HIV Testing [Internet]. National AIDS Control Organization, Ministry of Health & Family Welfare, Government of India, 2015 [cited 2019 Nov 26]. Available from: http://www.naco.gov.in/sites/default/files/Nationa_Guidelines_for_HIV_Testing_21Apr2016.pdf

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

3. 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/ 

4. 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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