Genotyping (Wild-Type vs. Vaccine Strain Differentiation)

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Accredited by the Standards Council of Canada to Laboratory no. 594 - CAN-P-4E (ISO/IEC 17025)

Requisition Forms

Reference Details

Description:

Genotyping of varicella-zoster virus (VZV) to differentiate between wild-type strain and vaccine strain.

Test Category:
Genotyping
Pathogen:
Varicella-Zoster virus (VZV)
Illnesses and Diseases:
  • Varicella (Chickenpox)
Specimen:

Lesion swab 1 mL (0.5 mL minimum), vesicular fluid 1 mL (0.5 mL minimum), CSF 0.6 mL (0.3 mL minimum ), whole blood 1 mL (0.5 mL minimum), or plasma 1 mL (0.5 mL minimum). Viral cultures 1 mL (0.5 mL minimum) may also be sent. Minimum volume will not allow repeat testing of samples with indeterminate results. Specimens must be confirmed to be VZV PCR positive before sending.

Collection Method:

For lesion swabs, place swabs in 2-3 mL of viral transport medium (VTM) for a minimum of 1 hour and then remove the swab. For vesicular fluid, aspirate fluid from fresh unbroken vesicle and mix with at least 200 µL VTM. 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 the tube at room temperature at 1,100 RCF for 10-15 min to separate the blood. Aliquot plasma into separate tube. Collect CSF in a dry tube subject to classic conditions for carrying out lumbar punctures. For viral cultures, collect infected cells and media.

Specimen Processing, Storage and Shipping:

Do not freeze whole blood; store and ship refrigerated within 48h of sample collection. Plasma, CSF, lesion swabs and fluid specimens 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.

For additional guidance on the transport of infectious substances in other languages, please click on the link below.

http://www.who.int/ihr/capacity-strengthening/infectious-substances/en/

Patient Criteria:

Immunization with attenuated VZV vaccine within the last month or when virus strain reactivation is suspected.

Accompanying Documentation:

Completed “Viral STI, Polyoma and Herpesvirus Testing” requisition form including sender lab name, address and telephone number, patient identifier, date of birth or age and sex, specimen reference #, type of specimen, date collected, test requested, and any other relevant clinical information. Include date of VZV vaccination and date of rash onset.

Comments:

This assay is for VZV strain differentiation only and has not been validated for VZV detection.

Methods and Interpretation of Results:

Strain differentiation of extracted DNA samples using real-time PCR methodology (1). Specific primers and hybridization probes differentiate Oka vaccine strain VZV from wild-type VZV strain based on the presence or absence of restriction sites within open reading frame ORF 38 and ORF 62. A melting curve analysis is used to determine whether the VZV strain is wild-type or vaccine strain. Inconclusive results may be confirmed by direct sequencing.

Turnaround Time:

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

Contact:
Phone: (204) 789-6024
Fax: (204) 318-2222
References:
  1. Tipples GA, D Safronetz, M Gray. A real-time PCR assay for the detection of varicella-zoster virus DNA and differentiation of vaccine, wild-type and control strains. J Virol Methods 2003; 113: 113-116.
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