Final answer:
The test that measures therapy effectiveness in an HIV positive client is the viral load test.
Step-by-step explanation:
The test that measures therapy effectiveness in an HIV positive client is the viral load test. This test detects the amount of HIV RNA (viral genetic material) in the blood. Monitoring viral load levels can help determine how well the antiretroviral therapy (ART) is working and whether the client's viral replication is being suppressed.