Herpes Simplex (HSV) and Varicella Zoster (VZV) Viruses Molecular testing

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Background
This page provides information on molecular testing for both Herpes Simplex Viruses and Varicella Zoster Virus at Public Health Ontario’s (PHO) laboratory.

This page is for information specific to molecular testing. For information regarding other testing options, refer to the following PHO webpages:

Updates

  • Combined HSV PCR TIS and VZV PCR TIS into one TIS document
  • Added testing information for HSV anti-viral resistance genotyping and VZV genotyping

Testing Indications

Virus culture will no longer be performed for HSV & VZV detection. Specimens will be tested for HSV1/HSV2/VZV at PHO using a more sensitive in-house real-time multiplex PCR method HSV-VZV PCR.

Polymerase chain reaction (PCR) testing for HSV and VZV is indicated for patients with compatible signs and presentations. 

For patients suspected of having anti-viral resistant Herpes Simplex Virus-1 (HSV-1) or Herpes Simplex-2 (HSV-2), characterized by no improvement (or relapse) in HSV-1 or HSV-2 lesions, HSV anti-viral resistance genotyping is available at the National Microbiology Laboratory (NML) in Winnipeg. Drug resistant HSV is more commonly isolated in immunocompromised patients.

Varicella genotyping is available at NML to differentiate between wild type and vaccine strain Varicella for those who have been immunized with attenuated VZV vaccine within the last month or when virus strain reactivation is suspected.

Acceptance/Rejection Criteria

Specimens collected using expired swabs or transport media tubes will be rejected

Check the expiry dates of both the collection swabs and transport media (tube), as specimens collected and received in incorrect containers or expired kits will be rejected for testing. In addition, specimens must meet the Criteria for Acceptance of Patient Specimens.

Specimen Collection and Handling

Specimen Requirements

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

Herpes Simplex Virus (HSV)

Swab of lesion/vesicular fluid

0.5ml

Virus Culture Collection Kit Order #390081

Varicella Zoster (VZV)

Swab of lesion/vesicular fluid

0.5ml

Virus Culture Collection Kit Order #390081

HSV resistance testing2

Swab of lesion/vesicular fluid (1ml); Plasma (1ml); Cerebral Spinal Fluid – CSF (0.6ml); Viral culture (1ml)

0.5ml

Virus Culture Collection Kit Order #390081

VZV genotyping3
VZV resistance testing4

Swab of lesion/vesicular fluid (1ml); Whole blood (1ml) Plasma (1ml); Cerebral Spinal Fluid – CSF (0.6ml); Viral culture (1ml)

0.5ml

Virus Culture Collection Kit Order #390081

HSV/VZV

Cerebral Spinal Fluid – CSF

1.0 ml

Sterile container

Submission and Collection Notes

1

Complete all fields of the General Test Requisition Form. Ensure the following fields are completed if diagnostic testing is requested:  

  • Patient setting
  • Symptoms (indicate all symptoms) and symptom onset
  • Specimen source (e.g. lesion)
  • Requesting healthcare provider’s CPSO#,
  • Complete mailing address, telephone, and fax number
  • Patient’s full name and address, date of birth, health card number (must match the specimen label)

Failure to do so may result in rejection or testing delay.

2

HSV resistance testing is referred out to National Microbiology Laboratory (NML) when clinically indicated. Refer to NML guidelines – Viral Exanthemata and STDs-Viral STI, Polyoma and Herpesvirus unit

3

VZV genotyping is referred out to the National Microbiology Laboratory (NML). Specimens must be confirmed to be HSV_VZV_PCR positive before sending. Genotyping (Wild-Type vs. Vaccine Strain Differentiation)

4

VZV resistance testing requires NML consultation and pre-approval by a PHO Microbiologist

5

Specimens that are not listed on the table will require pre-approval by PHO microbiologist, contact PHO’s Laboratory Customer Service Centre at 416-235-6556 or 1-877-604-4567 before submission. Critical samples may be considered for testing and will be reported with disclaimer.

6

Check the expiry dates of both the collection swabs and transport media (tube), as specimens collected using expired swabs or tubes will be rejected. In addition, specimens must meet the Specimen Acceptance Criteria

Storage and Transport

Specimens should be stored at 2-8°C following collection and shipped refrigerated to PHO on ice packs; if transport is delayed for more than 72 hours, stored at -80°C and ship on dry ice.

All clinical specimens must be shipped in accordance to the Transportation of Dangerous Good Act

Requisitions and Kit Ordering

Test Frequency and Turnaround Time (TAT)

Herpes simplex/ Varicella Viruses polymerase chain reaction (HSV_VZV_PCR) test is performed daily, Monday to Friday, at PHO’s laboratory, Toronto site, Hamilton and Kingston.

The TAT are listed in the table below.

Test

Turnaround Time (TAT)

HSV-VZV-PCR testing

Up to 4 business days from receipt at the PHO’s laboratory

Herpes Simplex Virus (HSV-1 & HSV-2) anti-viral resistance genotyping

Up to 10 calendar days upon receipt at NML

VZV genotyping

Up to 7 calendar days upon receipt at NML

STAT and Critical Specimens Testing

STAT testing is not available at Public Health Ontario’s laboratory

Test Methods

The HSV-VZV polymerase chain reaction (PCR) test is a Laboratory Developed Test (LDT) validated at PHO’s Laboratory. It is a multiplex assay that detects – Herpes Simplex Type 1 (HSV-1); Herpes Simplex Type 2 (HSV-2) and Varicella Zoster Virus (VZV).

PHO’s laboratory will issue report with all 3 target viruses results regardless of which targets has been requested on the requisition.

Tests perform at National Microbiology Laboratory (NML):
Herpes Simplex Virus (HSV-1 & HSV-2) anti-viral resistance genotyping is referred out to National Medical Microbiology (NML) when clinically indicated and requested on requisition.

VZV genotyping differentiates between the wild type and vaccine strains of VZV. It is referred out to NML when requested.

VZV resistance testing is referred out to NML when clinically indicated.

Interpretation

Results will be reported as DETECTED/NOT DETECTED/INDETERMINATE for HSV_VZV_PCR analysis at PHO’s Laboratory on all 3 viruses: HSV 1, HSV 2 and VZV upon each sample request:

  • An indeterminate PCR test result may be due to a low level of target genetic material in the specimen, inadequate specimen content, or a non-specific signal. Suggest to resubmit another specimen for testing if clinically indicated
  • This result must be interpreted within the context of the clinical history and epidemiological information.

A negative result does NOT exclude the possible presence of HSV/VZV virus.

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 positive for Varicella Zoster virus are reported to the Medical Officer of Health as per Health Protection and Promotion Act.

Specimens that are positive for Herpes Simplex from sterile sites (e.g. CSF) are reported to the Medical Officer of Health as per Health Protection and Promotion Act.

Mis à jour le 7 nov. 2024