Which of the following investigation is used in the detection and confirmation of HIV ?

Amount of virion packaged HIV 1 RNA in the peripheral blood is an impoant measure of disease activity and effectiveness of antiretroviral therapy. This genomic viral RNA can be measured by -PCR. HIV1 RNA detection assays are highly sensitive and specific for diagnosis of HIV1 infection. PCR is extremely sensitive but cross contamination can occur. The standard blood screening test for HIV infection is the ELISA. The most commonly used confirmatory test is the Western blot. Western blot demonstrates antibodies to products of all three of the major genes of HIV (gag, pol, and env). The CD4+T cell count is the laboratory test generally accepted as the best indicator of the immediate state of immunologic competence of the patient with HIV infection. The hallmark of HIV disease progression is decline in the absolute number and percentage of CD4 T lymphocytes and an increasing percentage of CD8 T lymphocytes. In the early weeks after acute HIV infection acquired by high-risk behaviors, HIV antibody may be absent. Most patients will seroconve by 6 weeks. Ref:Manual of Commercial Methods in Clinical Microbiology By Allan L. Truant, Page 101; Textbook of Pediatric HIV Care By Steven Leonard Zeichne, Page 106