HIV – PCR

Testing Indications

HIV-1/-2 NAT is used for the qualitative detection and differentiation of HIV-1 and HIV-2 RNA in human serum, plasma, and dried blood spots (DBS)*. The test is intended to be used as an aid in the diagnosis of HIV under specific conditions:

• infants born to HIV-positive or high-risk mothers;
• pregnant women;
• resolution of indeterminate HIV antibody test;
• diagnosis of acute infection prior to seroconversion (window period);
• transplant patients receiving immunosuppressive drugs.

*DBS is not Health Canada-approved but has been validated by PHO to be used for HIV PCR testing.

For more information on HIV testing recommendations, refer to Ontario Guidelines for Providers Offering HIV Testing.

Acceptance/Rejection Criteria

• Unspun primary blood collection tubes will be rejected.
• Plasma collected using anticoagulants other than EDTA will be rejected.
• Dried blood spot cards with spots not fully delineated with blood will be rejected.
• Donor testing is not available through PHO’s laboratory. Specimens from patients being screened as potential donors (e.g. organ, tissue, cells, fertility, etc.) should be referred to a laboratory that performs donor screening assays. Specimens received for donor screening at PHO’s laboratory will be rejected.

Limitations

Haemolysed, icteric, lipemic or microbially contaminated serum is not recommended for testing.

*DBS is not Health Canada-approved but has been validated by PHO to be used for HIV PCR testing.

Storage and Transport

Place specimen tube in biohazard bag and seal. Place completed General Test Requisition in the pouch at the front of the biohazard bag.

Serum or plasma must be centrifuged and separated within 24 hours of collection. Centrifugation should be performed according to the manufacturer’s instructions. Serum or plasma can be stored in secondary tubes for up to 24 hours at 30°C followed by up to 5 days at 2°C to 8°C or up to 6 weeks at ≤-20°C.

Specimen tubes should be stored according to recommend storage requirement as indicated above, and should be shipped to PHO’s laboratory as soon as possible.

All clinical specimens must be shipped in accordance to the Transportation of Dangerous Good Act.

Special Instructions

For testing of women at high-risk of HIV to guide management of the infant after delivery, “high-risk mother” must be indicated on the requisition for HIV PCR. Failure to do so may result in rejection.

Test Frequency and Turnaround Time (TAT)

HIV-1 PCR turnaround time is up to 5 business days from receipt by PHO’s laboratory. Testing is performed at least 3x during the week.

HIV-2 PCR negative results are reported within 5 business days. A HIV-2 RNA positive result is reported as presumptive positive and requires referral to the National Laboratory for HIV Reference Services (NLHRS) in Winnipeg for confirmation. Turnaround time is up to 14 days from receipt by PHO Laboratory.

STAT and Critical Samples Testing

STAT HIV-1 PCR testing may be considered on an individual basis for specific circumstances in consultation with a PHO Microbiologist (e.g. high risk woman in labour who are suspected to be in the window period). The PHO Microbiologist can be contacted through the PHO Laboratory's Customer Service Centre at 416-235-6556 / 1-877-604-4567.

STAT samples must be shipped separately from routine specimens in a clearly marked package indicating ‘STAT’ and handled in accordance with the Canadian Biosafety Standards and shipped in accordance with the Transportation of Dangerous Goods Regulations. Failure to ship separately will delay testing.

Specimens for HIV PCR are tested using the Roche cobas® HIV-1/HIV-2 Qualitative assay on the cobas 8800 system. The cobas® HIV-1/HIV-2 Qualitative assay is a NAT for the qualitative detection and differentiation of HIV-1 and HIV-2 RNA in human serum, plasma, or DBS. Specimens are tested simultaneously for HIV-1 and HIV-2, individual testing cannot be requested. HIV-2 PCR positive results are reported as presumptive positive and are referred to the National Laboratory for HIV Reference Services (NLHRS) for confirmation.

Table 1: Analytical sensitivity (limit of detection) of cobas® HIV-1/HIV-2 Qualitative assay

Interpretation

All test results should be interpreted in conjunction with the patient's clinical presentation, history and other laboratory results. The following table provides possible test results with associated interpretations:

Reporting

Results are reported to the physician, authorized health care provider (General O. Reg 45/22, s.18),  or submitter as indicated on the requisition.

Specimens that are reactive for HIV PCR are reported to the Medical Officer of Health as per the Ontario Health Protection and Promotion Act.