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Antiviral Resistance Genotyping

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Requisition Forms

Reference Details


Human cytomegalovirus (HCMV) anti-viral resistance genotyping.

Test Category:
Human Cytomegalovirus (HCMV)
Illnesses and Diseases:
  • Congenital infection

HCMV positive plasma 1 mL (0.5 mL minimum), whole blood 1 mL (0.5 mL minimum), or viral culture 1 mL (0.5 mL minimum). Minimum volume will not allow repeat testing of samples with equivocal results.

Collection Method:

For plasma, collect blood in plasma preparation tube (PPT) or K2EDTA tube (plastic; lavender or pink top). Do not use heparin as an anti-coagulant. Centrifuge tube at room temperature at 1,100 RCF for 10-15 min. Aliquot plasma into separate tube.

Specimen Processing, Storage and Shipping:

Do not freeze whole blood; store and ship refrigerated within 48h of sample collection. Plasma may be stored and shipped refrigerated to NML within 48h of sample collection or must be stored and shipped frozen. Viral cultures must be stored frozen at all times and shipped on dry ice.

Transportation of Dangerous Goods:

Shipping of specimens shall be done by a TDG certified individual in accordance with TDG regulations. For additional information regarding classification of specimens for the purposes of shipping, consult either Part 2 Appendix 3 of the TDG Regulations or section 3.6.2 of the IATA Dangerous Goods Regulations as applicable.

Patient Criteria:

Suspected anti-viral resistant HCMV, characterized by no improvement (or relapse) in CMV viremia or clinical diseases during antiviral therapy (6 or more weeks) (3).

Accompanying Documentation:

Results of HCMV PCR including copy number. Completed "Viral STI, Polyoma and Herpesvirus Testing" requisition form including sender lab name, address and telephone number, patient identifier, sex, specimen reference #, type of specimen, date collected, test requested and any other relevant clinical information.



The specimen should be positive for HCMV DNA and results included with the requisition form.


Methods and Interpretation of Results:

Regions of the protein kinase (UL97) and polymerase (UL54) HCMV genes that harbour known anti-viral resistant mutations are amplified by PCR and sequenced. The HCMV sequence data is then analyzed with an online tool (1,2) that links HCMV anti-viral resistance mutations to reported resistance phenotypes. The submitted sequence is compared via BLAST to wild-type reference sequences and mutations are identified. These mutations are cross-checked to a regularly-maintained database of all published mutations to determine whether they confer sensitivity or resistance to Ganciclovir, Cidofovir, Foscarnet and other antivirals.  Upon special request, regions of UL56 and UL89 can be assessed for Letermovir resistance. Interpret results with caution as this assay is for research purposes only.

Turnaround Time:

10 calendar days. STAT samples may be considered under special circumstances. Please contact the lab to inquire about shorter turn around time.

Phone #: (204) 789-6024
Fax: (204) 318-2222
  2. Chevilotte, M et al., 2010. A new tool linking human cytomegalovirus drug resistance mutations to resistance phenotypes. Antiviral Research 85: 318-327.
  3. Transplantation. 2013; 96:1.
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