Quick Review Cards for Medical Laboratory Science

HIV Screening Tests Immunology Review 407

TEST

EIA/ELISA

1st generation

2nd generation

3rd generation

4th generation

Rapid tests

Nucleic acid

amplification

testing (NAAT)

COMMENTS

EIA or CIA. P24 ag without HIV ab = acute infec-

tion. P24 ag & HIV ab = established infection.

Currently not approved for screening blood

donors.

Immunochromatographic assays. Can be per-

formed on whole blood, serum, oral fluid.

Not cost effective for screening in most settings.

Used for screening blood donors & infants. (Ab

tests aren’t reliable in children <18 months of

age. Abs from infected mother can be present

even if child isn’t infected.)

DETECTS

IgG ab to HIV-1

IgG ab to HIV-1/2

IgG & IgM ab to HIV-1/2

IgG & IgM ab to HIV-1/2 & p24 ag

IgG & IgM ab to HIV

HIV RNA

WINDOW PERIOD*

6–12 wk

6–12 wk

3–4 wk

2 wk

4–12 wk

5 days

All specimens with pos screening tests must be tested again by same or different screening test. If repeatedly pos, a confirmatory/supplemental test must be done.
*Time between exposure & pos test result.