Western Blot Information

The Western blot test is an HIV blood test which confirms a previous positive HIV test. In some cases, medical personnel use the Western blot test to determine if someone has Lyme disease.

Reason for Use

• Medical professionals consider the Western blot test more precise than the ELISA HIV test. Both tests detect the presence of certain antibodies in the blood. However, the blot test identifies proteins, while the ELISA test is enzyme-linked.

Significance

• A Western blot test always follows a positive ELISA test. A negative Western blot test determines the previous ELISA test was a "false positive" result. Western blot tests can also be inconclusive, and additional testing might be necessary.

Diagnosis

• Negative ELISA and Western blot tests do not completely rule out HIV infection. There is a six-month "window" period in which HIV antibodies are too low in number to appear in the tests. Additional testing might be necessary at different periods to be 100 percent certain of negative HIV infection.

Lyme Disease

• In most cases, a simple bacterial-based blood test determines if someone has Lyme disease. However, if a person develops central nervous problems, then a Western blot test rules out other diseases, like meningitis.