Virology / Serology - HIV
Two HIV serologic assays are utilized as part of an HIV testing algorithm. Initial screening for HIV-1 p24 antigen and antibodies to HIV-1 (including Group O and subtypes) and HIV-2 is performed using as immunoassay (IA). All reactive IAs are repeated in duplicate to verify the initially reactive test result. All repeatedly reactive IA tests (two or more reactive) are tested by the Multispot HIV-1/HIV-2 discriminatory assay that differentiates HIV-1 and HIV-2. Patients who test HIV-1 positive on the Multispot assay should be considered HIV infected. If the test result indicates HIV-2 reactivity, the sample is referred to CDC for HIV-2 confirmation.
Patients who test nonreactive for HIV p24 antigen and HIV-1/HIV-2 antibodies by the IA screening assay can be considered negative for both acute and established HIV infection. Samples that test repeatedly reactive on the screening assay but test as either nonreactive, HIV positive (undifferentiated), HIV-1 indeterminate, or invalid by Multispot are further tested for HIV-1 RNA by nucleic acid amplification (NAAT). Patients with detectable HIV-1 RNA should be considered as likely acute HIV infections.
At least 3mL of serum is required for the complete HIV testing protocol.
Specimen Acceptance Policy
Serologic screening for human immunodeficiency virus (HIV) infection is available only through designated counseling and testing sites. Only serum samples are acceptable for HIV testing. Specimens submitted to the Virology/Serology Unit must be accompanied by a fully completed HIV OCR scannable submission form. Failure to supply the requested information may result in significantly delayed specimen testing. Improperly submitted specimens will be stored for ten days pending verbal and/or written notification of the submitter. Unless alternate arrangements are initiated by the submitter upon notification of specimen rejection, the specimen will be discarded at the end of the holding period.
A full 3 mL of serum should be submitted for HIV testing. Aseptically collect whole blood in a red top tube or in a serum separator tube. Let specimen stand 30 minutes to ensure complete clotting of the blood. Centrifuge for 5-10 minutes at 1,000-1,500 xg. Transfer serum to a well constructed plastic screw-capped vial with threads on the outside. Serum transport tubes should not be overfilled past the 3.0 mL line on the tubes. Excessively hemolyzed or extremely lipemic sera are unacceptable for HIV assays. Specimens which are not acceptable for testing will be reported UNSATISFACTORY.
Label each vial of serum with the patient's first and last name and either the date of birth, Social Security number, or other unique identifier. A pre-printed HSIS label may be used. Complete the HIV submission form in its entirety. All items on this form must be completed before the specimen can be processed.
Scannable forms should be placed inside an envelope with cardboard to ensure that the form arrives at the lab without folds, tears or wrinkles and the return address and collection date should be recorded on the envelope in the marked space in the upper left-hand corner. Specimens should be placed inside a plastic bag and then placed into the mailer marked "CTS Serology" and the return address and date of collection entered on the outside in the marked space. If Courier service is used, the appropriate courier barcode should be affixed to the front of the envelope and both the envelope with the scannable forms and the specimen mailer should then be placed inside a large plastic bag and sealed. Specimens for other laboratory services should not be placed in this bag. Specimens can be shipped at ambient temperature.
Forms are available to Counseling and Testing Sites through the Virology/Serology Unit Office, telephone (919) 733-3937. Envelope mailers for forms, plastic screw-capped vials and color-coded mailers for specimens are available via online ordering at this website.
The following chart provides information regarding turn-around-times and interpretations. A brief statement of the "normal" values for each assay is given under the heading "Negative Reference Range":
|Test||Test Method||Negative Reference Range||Turnaround Time|
|Human Immunodeficiency Virus type 1 (Groups M & O) and type 2 antibodies; HIV p24 antigen||IA-Qualitative||No antibody or p24 antigen detected||2 working days|
|Human Immunodeficiency Virus type 1||Rapid EIA-Qualitative||No antibody detected||3 working days|
|Human Immunodeficiency Virus type 1 RNA||Nucleic Acid Amplification Test (NAAT)-Qualitative||No HIV-1 RNA detected||5 working days|
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