Hepatitis C – Genotyping/Subtyping

Testing Indications

  • Hepatitis C virus (HCV) genotyping is tested in conjunction with a detected HCV RNA viral load.
  • All specimens submitted for HCV RNA viral load without a previous HCV genotype that meets HCV genotype testing requirements will be automatically tested for HCV genotype.
  • HCV genotyping will be automatically repeated for patients with suspected HCV reinfection (as indicated on the test requisition) , as long as the HCV viral load meets the testing requirements.

Specimen Collection and Handling

Specimen Requirements

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

HCV Genotyping

Serum1

1.0 ml

Blood clotted- vacutainer tubes (SST)

HCV Genotyping

Whole Blood2

5 ml

SST or any tubes without additive2

Submission and Collection Notes

1

Freshly drawn whole blood specimens collected in serum separator tubes (SST) may be stored and/or transported at 2°C to 25°C for up to 24 hours before centrifugation. Following centrifugation, remove serum from cells immediately, and transfer serum into screw-capped cryovial tubes. Serum specimens may be stored and/or transported at 2°C to 8°C for up to 72 hours or at ≤-18°C for up to 6 weeks. If more extended storage of serum specimens is required, it must be frozen at ≤-60°C.

2

Unspun whole blood must be received at Public Health Ontario’s (PHO) Laboratory within 24 hours of collection before 2:00 p.m. Monday – Friday.

Limitations

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

Special Instructions

Complete the Hepatitis PCR Requisition: Hepatitis C RNA and/or Hepatitis B DNA viral load. To avoid cancellation and facilitate timely testing, complete all fields on the requisition. Date and time of collection must be recorded on the test requisition.

Requisitions and Kit Ordering

Test Frequency and Turnaround Time (TAT)

HCV genotyping testing is performed 3 times a week Monday to Friday.

Turnaround time is up to 10 days from receipt by PHO’s laboratory.

Reporting

Results are reported to the ordering physician or health care provider as indicated on the requisition.

Test Methods

Specimens for HCV genotyping/subtyping are tested using the Roche cobas® HCV GT assay, which is a real-time reverse transcription-polymerase chain reaction (RT-PCR) assay for the qualitative detection of HCV genotypes 1 (including subtypes a and b), 2, 3, 4, 5, 6.

The LOD of the cobas® HCV GT is 50 IU/mL for genotype 2, 125 IU/mL for genotypes 1a, 1b, 3, 4, and 6 and 500 IU/mL for genotype 5.

Algorithm

HCV specimens must have a detectable viral load of at least 125 IU/mL for HCV genotyping to be performed. The first pre-treatment (baseline) specimen submitted for HCV RNA viral load testing will be automatically tested for HCV genotype if it meets the minimum viral load requirement.

Note: HCV genotype 5 is relatively uncommon in Canada, however, it may be missed in specimens with a viral load <500 IU/ml.


Interpretation

The detected genotype/subtype is reported. If a genotype cannot be determined, the result is reported as “Indeterminate”. If warranted, Indeterminate specimens will be sent to the National Microbiology Laboratory for further testing.

contact lab

Contact Laboratory Customer Service

Laboratory Services

customerservicecentre@oahpp.ca

Updated 29 April 2022