HIV ELISA/Western blot

Alternative names:

ELISA/western blot - HIV; western blot

Normal values:

A negative test result is normal.

What abnormal results mean:

The ELISA is used as a screening test. A positive result does not necessarily mean that the subject has exposure to the HIV virus or HIV disease. The western-blot is used as a confirmatory test, and may be negative, positive, or indeterminate. A positive western blot is generally regarded as conclusive for an HIV infection. Negative tests do not necessarily rule out HIV infection, because there is a time interval between HIV infection and the appearance of measurable anti-HIV antibodies (the so-called "window period"). An infected individual may transmit HIV during the window period (even with a negative anti-HIV ELISA or western-blot test).

Note: Studies have shown that a recent flu shot can result in a false positive HIV ELISA. However, if this is the reason you tested positive the western-blot test will confirm that you are HIV negative. After about 3 months the HIV ELISA will convert back to a negative result. Inform your health care provider if you are considering having this test performed and have had a flu shot within the past 3 months.

Update Date: 04/01/00
Luis A. Diaz, Jr. M.D., Johns Hopkins Medical Institute, VeriMed Health Network