HIV – PCR

Consistent with O. Reg. 671/92 of the French Language Services Act, laboratory testing information on this page is only available in English because it is scientific or technical in nature and is for use only by qualified health care providers and not by members of the public.

Background
This page provides qualitative nucleic acid test (NAT) information for human immunodeficiency virus types 1 and 2 (HIV-1/-2), which are the causative agents of acquired immunodeficiency syndrome (AIDS), at Public Health Ontario (PHO). For information regarding other testing options, refer to the following PHO webpages:

Updates

  • Effective May 29th, 2023, qualitative HIV PCR testing changed to the Health Canada-approved cobas® HIV-1/-2 qualitative NAT assay on the Roche system. 
  • Updated submission and collection notes to provide clarity on handling requirements between blood collected in blood tubes with and without gel separators.

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. Spun PPT and SST are acceptable.
  • 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.

Specimen Collection and Handling

Specimen Requirements

Test Requested Required Requisition(s) Specimen Type Minimum Volume Collection Kit

HIV-1/-2 PCR

Serum or Plasma

750 μl for PCR only or 1.2 mL if HIV Serology is required

Serum separator tubes (SST), BD Vacutainer Plasma Preparation Tubes (PPT) or equivalent collection tube with EDTA as anticoagulant

HIV-1/-2 PCR

DBS3

1 card

Whatman 903 Cards or equivalent

Submission and Collection Notes

1

Specimens may be stored at 2°C to 25°C and must be centrifuged within 24 hours of collection. If using blood collection tubes without gel separators, serum or plasma must be separated and transferred to aliquot tubes immediately before sending to PHO. Spun SST or PPT can be sent to PHO, but a separated and aliquoted serum or plasma is preferred. Centrifugation should be performed according to the tube 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.

2

DBS cards must have at least four (4) fully delineated spots that are allowed to dry completely before submitting to PHO. DBS must be transported to PHO in individual sealable bags containing a desiccant sachet at room temperature. Appropriately prepared DBS specimens are stable at room temperature for up to 30 days. PHO does not provide supplies for DBS collection and shipping.

Supplies may be ordered from the following suppliers:

DBS collection labelling table

3

Complete all fields of the requisition form, including:

  1. Test(s) requests and indications for testing
  2. Patient setting, specimen type and site
  3. Relevant clinical information
4

Label the specimen container(s) with the patient’s first and last name, date of collection, and one other unique identifier such as the patient’s date of birth or Health Card Number. For additional information, see: Criteria for Acceptance of Patient Specimens. Failure to provide this information may result in rejection or testing delay.

5

Do not submit glass tubes.

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.

Specimen tubes should be stored according to recommend storage requirements 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.

Requisitions and Kit Ordering

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.

Test Methods

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

Specimen Type HIV-1 HIV-2
EDTA Plasma 12.8 copies/mL 35.4 copies/mL
Serum 12.8 copies/mL 26.3 copies/mL
DBS 255 copies/mL 984 copies/mL

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:

Result

Interpretation

Comments

HIV-1/HIV-2 not detected

No HIV-1 or HIV-2 RNA detected.

A non-reactive test result does not exclude the possibility of infection with HIV. Persons in high risk groups who are non-reactive should be retested for up to three (3) months following possible exposure to HIV or on presentation of symptoms compatible with HIV infection.
False negative (non-reactive) results may be obtained when testing individuals undergoing anti-retroviral therapy (ART) or taking pre-exposure prophylaxis (PrEP) or post-exposure prophylaxis (PEP).

HIV-1detected

HIV-2 detected

HIV-1/HIV-2 detected

HIV-1 RNA detected.

HIV-2 RNA detected.

HIV-1 and HIV-2 RNA detected.

Pregnant patients and infants (less than 24 months of age) should be referred to a Paediatric HIV specialist for counselling on vertical HIV transmission prevention and/or management of the newborn, and for follow-up testing.

Invalid

Unable to determine result due to interfering substances.

Recollect and submit a new specimen for testing.

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.

contact lab

Contact Laboratory Customer Service

Laboratory Services

customerservicecentre@oahpp.ca

Updated 12 Oct 2023