HIV serology

Keywords: HIV antibody, Human immunodeficiency virus test

Specimen:

10 mL blood in plain tube. Informed consent must be obtained from the patient prior to ordering the test.

Method:

Immunoassay for detection of both HIV-1 and HIV-2 antibodies. Specialised laboratories confirm positive immunoassay results by immunoblot methods.

Reference Interval:

Positive is significant, if confirmed by immunoblotting.

Application:

Diagnosis is of HIV infection. Screening of blood, tissue or organ donors. Following exposure, the seronegative "window" period may be from 3 weeks to several months. Occasional subtypes of HIV may be undetectable by some EIA methods.

Interpretation:

Positive indicates HIV infection and must be confirmed by immunoblot and by testing on a separate sample. False positives are rare, and can be further assessed by immunoblot, tests for HIV antigen or, preferably, HIV-1 RNA and repeat HIV antibody testing; see HIV p24 antigen, HIV-1 RNA. In terminal disease, HIV antibodies may be negative. HIV-1 is common worldwide; HIV-2 is less common and is largely confined to Africa.

Patients where there is a high clinical suspicion and are negative for HIV antibody should undergo p24 antigen testing or Proviral DNA assay.

Reference:

Schleupner CJ. In Mandell GL et al eds. Principles and Practice of Infectious Diseases. 4th ed. 1995. Churchill Livingstone.

Gaines H et al. Lancet. 1987; 1:1249-1253.