Final answer:
A negative HIV ELISA test after a needle stick does not guarantee that the person is not infected with HIV, and further testing may be necessary to confirm the results.
Step-by-step explanation:
When an HIV ELISA test is negative for a person who had a needle stick, it means that the test did not detect any HIV antibodies in their blood. However, it is important to note that a negative ELISA test does not definitively exclude the possibility of HIV infection, especially if the test was done shortly after the exposure. This is because it takes time for the body to produce enough antibodies to be detected by the test, a period known as the seroconversion window.
If there is a concern about a possible false negative, follow-up tests such as a western blot or a nucleic acid test may be performed to confirm the presence or absence of HIV.
In summary, a negative HIV ELISA test after a needle stick does not guarantee that the person is not infected with HIV, and further testing may be necessary to confirm the results.