Gửi bạn 1 ít thông tin để bạn tham khảo,

Lưu ý về cách dùng từ của họ,

Đọc xong bạn sẽ hiểu vì sao là gián tiếp và vì sao lại trực tiếp,

Nên có kiến thức chuẩn trước khi tư vấn.

Chúc các bạn sớm hoàn thiện kiến thức để đóng góp cho diễn đàn và xã hội.

What are the different types of HIV testing?

There are three main types of HIV tests: antibody tests, RNA tests, and
a combination test that detects both antibodies and viral protein called p24.

....

HIV antibody tests: HIV possesses many unique proteins on its surface and inside the virus itself. When someone is infected with HIV, their body produces substances designed to neutralize the virus. These substances are called antibodies, and they are directed against the unique proteins of HIV. Unfortunately, these HIV antibodies do not eliminate the virus. However, their presence serves as a marker to show that someone is infected with HIV. HIV
antibody tests are the most commonly used tests to determine if someone has HIV.

....

HIV RNA tests: The HIV RNA is different than all human RNA, and tests have been developed to detect HIV RNA in a person's blood. This uses a type of test called a polymerase chain reaction (PCR). These tests are important for newborn
screening of HIV-positive mothers since maternal antibody may cross the placenta
and be present in the newborn. These tests may also be helpful in detecting
early HIV infection before antibodies have fully developed (about four weeks from
infection). However, they are costly and are not routinely used to screen for infection.

HIV combination test: The HIV combination test detects antibodies directed against HIV-1 or HIV-2, as well as a protein called p24, which forms part of the core of the virus. This is important because it
takes days or weeks for antibodies to form after the initial infection,
even though the virus (and the p24 protein) is present in the blood.
Thus, combination testing may allow for earlier detection of HIV
infections. Early results suggest that diagnosis could be made an
average of one week earlier using the combination test, compared to
antibody testing alone. The test uses a reaction known as
"chemiluminescence" to detect antibodies and p24 protein. In other
words, if either the antibody or the p24 protein is present, the test
reaction emits light which registers on a detector. There is only one
currently approved combination test, the Architect HIV Ag/Ab Combo
assay. If this test is positive, it is recommended it be repeated.
Tests that remain positive are confirmed with Western blot as described above.

http://www.medicinenet.com/hiv_testing/page2.htm