Hepatitis C viral loads
Microbiology
Notes
Hepatitis C virus (HCV) viral load is the quantifiable measurement of HCV RNA in human serum or plasma
Further tests for HCV positive patients include HCV genotype testing
The optimal time from specimen collection to separation is 6 hours
Sample requirements
Plasma - paired samples not required (serum is accepted for HCV viral loads only)
4ml of blood taken into an EDTA Tube
For adults 2 full EDTA tubes are required for each test - eg. for HCV viral load and genotype, 4 EDTA tubes in total are required.
For babies and small children a minimum of one full 2mL paediatric EDTA or one full paediatric Mini Collect EDTA tube is required
Required information
- Relevant clinical details
- Time of sample collection
Storage/transport
Transport immediately at ambient temperature
Turnaround time
Adult HCV viral loads:
Tested in house
Up to 10 days
Paediatric HCV viral loads:
Sent to a Regional Reference Centre
Up to 10 days
Results
Reported in IU/mL and log IU/mL
| In house assay | Lower limit of detection: | 10 IU/mL | <1.00 log IU/mL |
| Upper limit of detection: | 100 million IU/mL | 7.0 log IU/mL | |
| Reference Centre assay | Lower limit of detection: | 12 IU/mL | 1.08 log IU/mL |
| Upper limit of detection: | 100 million IU/mL | 7.0 log IU/mL |
Result interpretation
- The assay is subject to some natural variation, but we would not expect this to exceed a 0.5 log difference when testing the same patient sample on two separate occasions. This also means that two separate samples from the same patient may naturally vary by up to 0.5 log without any underlying change in viral load and that samples may on occasion fluctuate around the cut-off from negative to positive or vice versa.
- Where two consecutive samples show an increase in viral load less than 0.5 log without an obvious cause we would remark on this in the report. i.e.
"This result and the previously reported result remain within the accepted normal variablilty of the assay (0.5 log IU/mL)."
- Where two consecutive samples show an increase in viral load greater than 0.5 log without an obvious cause we would automatically re-test the most recent sample if sufficient sample remains.
- Where two consecutive samples show a change from negative to positive regardless of the degree of difference we would automatically re-test the most recent sample if sufficient sample remains.
- Where a sample is repeated we will report both results.
- Based upon our own data for 2013 the variability of the assay has not exceeded 0.41 log
- See also: