Virology / Serology - HIV
Three serologic assays are available for the detection of antibodies to the human immunodeficiency virus (HIV). An enzyme immunoassay (EIA) is used as a screening test for antibodies to HIV-1 (including Group O subtypes) and HIV-2. All reactive EIAs are repeated in duplicate to verify the initially reactive test result. All repeatedly reactive EIA tests (two or more reactive) are tested by the Western blot HIV-1 (WB) assay. All HIV specimens that test nonreactive for HIV antibodies by the EIA screening assay are then tested for HIV-1 RNA using molecular methodology to detect acute HIV infections. Samples that test repeatedly reactive on the screening assay but fail to test as reactive/positive by HIV-1 WB or HIV-1 RNA are further tested by a third serologic assay that differentiates HIV-1 and HIV-2. At least 3mL of serum is required for the complete HIV testing protocol.
Specimen Acceptance Policy
Specimens are accepted from the following:
- Serologic screening for human immunodeficiency virus infection is available only through designated counseling and testing sites. Sera which are reactive in the initial test (enzyme immunoassay) are retested. Repeatedly reactive sera are automatically tested by a supplemental test method (Western blot). Specific interpretation of the laboratory findings are an integral part of the laboratory report.
- The Western blot supplemental serologic test for human immunodeficiency virus infection is available as a reference service to public health care providers. Sera will be accepted for testing provided that the submitter states that serologic screening test results are repeatedly reactive. Specific interpretation of the Western blot findings are an integral part of the laboratory report.
Only serum samples are acceptable for HIV testing on a routine basis. 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 or Social Security number. 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 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 temperatures.
Forms are available to Counseling and Testing Sites through the Virology/Serology Unit Office, telephone (919) 733-7544. Envelope mailers for forms, plastic screw-capped vials and color-coded mailers for specimens are available via online ordering at this website. Submitters of reference specimens for Western blot serology should use DHHS Serology Form #3445 (PDF, 385 KB) and the "Special Serology" mailer.
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||Turn-Around-Time|
|Human Immunodeficiency virus type 1 (Groups M & O) and type 2 antibodies||EIA-Qualitative||No antibody detected||10 working days|
|Human Immunodeficiency virus type 1 antibody||Western blot-Qualitative||No antibody detected||5 working days|
|Human Immunodeficiency virus type 1 RNA||Nucleic Acid Amplification Test (NAAT)-Qualitative||No HIV-1 RNA detected||10 working days|
|Human Immunodeficiency virus type 1 (Groups M&O) and type 2 antibodies||Rapid EIA-Qualitative||No antibody detected||10 working days|
The State Laboratory of Public Health uses the APHL/CDC criteria shown below for the interpretation of the Western blot.
|Negative||The absence of any and all bands - not just viral bands.|
|Indeterminate||The presence of any other band or bands that fail to meet the positive criteria.|
|Positive||The presence of any two of the following bands:
The following recommendations are made regarding follow-up specimens:
- If patient HIV infection status is inconclusive based upon test results, submit another specimen for testing within a month. If test results for the second specimen are also inconclusive for HIV infection status, the patient should be tested again at six months
- When a patient receives his/her first positive test result a verification specimen should be collected at the time the patient is given the results of the first test.
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