The ELISA (Enzyme-Linked Immunoabsorbent Assay) test is used to screen blood
products and individuals at increased risk for HIV infection.
If positive (reactive), the test is usually repeated on the same blood
sample. Although this is a sensitive test, it is not highly specific for HIV
(other conditions may give a positive ELISA).
For that reason, before HIV can be confirmed, an additional test is
- Western Blot (WB), or
- Indirect Fluroescent Antibody (IFA)
If either the WB or IFA is positive, the diagnosis of HIV infection is
In the event the ELISA is positive, but the WB or IFA is negative, a
repeat of the WB or IFA in 3-6 months is often recommended.
*These are general values taken from a variety of
sources. The actual normal values may vary from lab to lab and from one
type of testing protocol to another.