There are two main types of HIV: HIV-1 and HIV-2. The more common type HIV-1 has several groups and subtypes [1].

Do all of these show up on routine HIV blood tests?

1 Answer 1


The big problem with HIV is its variability. HIV-1 and HIV-2 are genetically 40 percent different - and that's in the most conserved regions. Some of the subgroups of HIV-1 have similar values.

This led to HIV-2 and HIV-1 subgroup O, in the past, often not being detected by standard HIV tests, leading to false negatives.

Subgroup O

False-negative results by HIV serologic assays have been verified when testing some individuals infected by HIV Group O viruses. This group of viruses, found primarily in Cameroon and Gabon, also has been reported in Europe and the United States. Several "acceptable" routine HIV screening assays have been documented to produce false-negative results in up to 20% of sera from individuals infected with Group O viruses.

[University of California, San Francisco]


Diagnostically, HIV-2 infections can present problems. Screening tests designed to detect infection by HIV-1 do not always detect infection by HIV-2 and vice versa.

[University of California, San Francisco]

Blood tests for HIV-1 and HIV-2

Blood tests that are capable of testing for all of these varieties, with an acceptable false negative rate, have been available for some time. The CDC recommendation to test for both in donated blood dates back to 1992, but because of the low incidence of HIV-2 outside of West Africa, did not yet recommend it for routine tests other than for blood meant for donations, in the absence of symptoms pointing to HIV.

The latest recommendation from 2014 specifies that

testing begins with a combination immunoassay that detects HIV-1 and HIV-2 antibodies and HIV-1 p24 antigen

And further recommends differentiating between HIV-1 and HIV-2. This type of test is also suitable for detecting HIV-1 subgroup O. I assume this recommendation has been in place for longer than 2014.

So, that's the recommendation. Is this actually being used in routine blood tests?

Looking at the section for HIV of one catalog of medical tests, the combined tests appear to be the standard, while the ones marked as either HIV-1 or HIV-2 are for further genotyping. I am assuming this is the standard test. So that would be a yes.

  • Still looking for a bit of info on subgroup O, but that's the status of my research so far
    – YviDe
    Commented Dec 1, 2015 at 12:12

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