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Test Code LAB5635 HIV 1/2 Antibody plus P24 Antigen

Additional Codes

Testing Algorithm: If reactive, antibody differentiation testing will be referred to BJS IOH Laboratory to be performed at additional charge

Performing Laboratory

St. Louis Children's Hospital Laboratory - Chemistry

Specimen Requirements

Patient Preparation: None

Collection Container/Tube:

Preferred: Gold SST gel tube

Acceptable: Plain red-top tube, Lavender-top (EDTA) tube or Mint green-top Lithium Heparin (MNTGRN LiHep) tube

Submission Container/Tube: If specimen is coming from outside facility and collected in a plain red-top tube or lavender-top tube aliquot processed sample into a plastic vial for transport (labeling with specimen type).

Specimen Collection Volume: 2.0 mL (minimum 1.0 mL)

Special Instructions: None

 

Sample Rejection

Specimens that are grossly hemolyzed

Specimens with obvious microbrial contamination

 Mislabled or unlabeled specimens

Logistics

Test Availability: Monday-Sunday

Cut-off time: None, performed as received

Turnaround Time: Same Day; 2 hours from receipt in performing lab

Reference Values

Reference Interval: Non-reactive (reported as reactive or non-reactive)

NOTE: 1. Negative result does not exclude the presence of HIV infection because undetectable quantities of antigen or antibody may be present, particualarly in acute infection. If clinically indicated, recomment repeat testing after 4-6 weeks.
  2. Reactive specimens that do not confirm by subsequent analysis performed may be due to false-positive screen or early infection. Consider testing for HIV RNA (viral load) to establish early infection.

Critical Value: None

Methodology

Electrochemiluminescence immunoassay (ECLIA) - sandwich principle

Limitations

  • The performance of this assay has not been established for individuals younger than 2 years of age. Nearly all infants born to HIV infected mothers passively acquire maternal antibody and, in some cases will test antibody positive until age 18 months regardless of whether they are infected. Definitive diagnosis of HIV infection in early infancy requires other assays, including HIV nucleic acid tests or virology culture.

Additional Information

FOR SLCH CORE LABORATORY USE ONLY

Lab Processing Instructions: Centrifuge to separate. If specimen is collected in microtainer or plain red-top tube aliquot sample into a Roche false-bottom tube for testing (labeling aliquot with specimen type).

Processed Volume: 0.5 mL serum/plasma

Analyte Stability:

Specimen Type Temperature Time
Whole Blood (unprocessed)  Ambient NA
Plasma/Serum (processed) Refrigerated (preferred) 7 days      
  Ambient  3 days
  Frozen  6 months   

 

Test Classification and CPT Code

87389

86701 (if appropriate)

86702 (if appropriate)

LOINC

HIV 1/2: 56888-1

80203-3 (if appropriate)

 

Last Reviewed

06/2025