[Diagnosis of HIV infection and AIDS]

The diagnosis of HIV infection is established by two steps, screening assays and confirmatory assays. The screening assays are designed to detect all infected individuals, and possess a high degree of sensitivity. The confirmatory assays are designed to identify individuals who are not infected but who have reactive screening test results, and have a high specificity. Tests with high sensitivity produce few false-negative results, whereas tests with high specificity produce few false-positive results. The most important step in evaluating an indeterminate result is assessing the patient's risk factors. The diagnosis of AIDS is defined as having HIV infection and getting one of AIDS-related disorders, which are unusual in people with a healthy immune system.