Final answer:
The hospital conducted widespread HIV testing due to potential exposure from contaminated syringes, using serological and nucleic acid tests to ensure early detection and prompt treatment to slow disease progression.
Step-by-step explanation:
The hospital felt it was necessary to test every patient for HIV due to the potential exposure from a rogue employee who compromised syringes. Testing for HIV is vital for early detection, which is crucial in slowing down the progression of the disease. Various tests can be used for diagnosis, including serological tests for antibodies and/or HIV antigens and nucleic acid tests (NAT) for the presence of the virus.
Following exposure to HIV, there's a window period where serological tests may not detect the infection because the body has not yet produced detectable levels of antibodies. This is why appointments for HIV screening were scheduled a minimum of 3 weeks after the patients' last hospital visit. In cases of positive ELISA tests, further confirmation through a Western blot test is required. If the Western blot is indeterminate or if early detection is needed, a PCR test is used to detect viral RNA, confirming the presence or absence of HIV sequences.