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Hemagglutination Inhibition (HI) Assay

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Reference Details


Serological detection of total antibodies (IgM and IgG) directed towards Powassan (POW) virus by Hemagglutination Inhibition (HI) assay.

Test Category:
Powassan virus
Illnesses and Diseases:
  • Powassan encephalitis

Serum. Minimum volume of 400 µL required. 

Collection Method:

2 mL screw cap tube.

Specimen Processing, Storage and Shipping:

Store samples refrigerated or frozen until shipped for testing. Ship frozen samples on dry ice, and refrigerated samples on wet 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 infection with Powassan virus and exposure to relevant arthropod.

Accompanying Documentation:

Completed Viral Zoonoses requisition including sender laboratory name, address and telephone number. Patient name and / or identifier (specimen reference number), date of birth, test(s) requested, collection date of specimen, date of on-set of symptoms, and clinical and travel history of patient.


To demonstrate seroconversion, both acute and convalescent samples must be tested in parallel.

Methods and Interpretation of Results:

The HI assay is used to measure the level of antibodies in a patient’s serum that will prevent the agglutination of susceptible erythrocytes by inactivated antigens that are able to attach to the erythrocyte receptors on red blood cells.  A fourfold or greater increase or decrease in titre between the acute phase and convalescent phase serum is considered to be diagnostic of infection with the virus used in the test or with an antigenically related virus (another member of the Flaviviridae family).  Results are expressed as the reciprocal of antibody titre. 

Due to the cross-reactive nature of anti-flavivirus antibody, (i.e. dengue, etc.) detection of total anti-POW virus specific antibody in a single serum sample is indicative of past or present exposure to this agent, or a related agent from the same virus genus. A 4-fold rise or greater in neutralizing antibody titre is required to document a "confirmed case" of infection with associated illness.

Isolation of an arbovirus, detection of specific antibody by plaque reduction neutralization assay or detection of nucleic acid by real-time RT-PCR in a clinical specimen would constitute firm evidence of viral association with illness and provide "confirmed case" status.

Turnaround Time:

14 Calendar days.

Phone #: (204) 789-7037
Fax: (204) 789-2018
  1. Clarke, D.H. and Casals, J. Techniques for hemagglutination and hemagglutination-inhibitiion with arthropod-borne viruses. Am. J. Trop. Med. And Hyg. 1958; 7: 561-573.
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