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Indirect Immunofluorescence Assay (IFA) – IgG

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Reference Details


Detection of IgG antibodies to Ehrlichia chaffeensis by IFA.

Test Category:
Ehrlichia chaffeensis
Illnesses and Diseases:
  • Ehrlichiosis

Fresh human serum. 

Minimum volume required is 0.25 mL. 

Hyperlipemic, hemolytic or contaminated sera may yield erroneous results.

Collection Method:

Collect blood in serum separator tubes.

Specimen Processing, Storage and Shipping:

Transfer an aliquot of serum to a 1.5 ml screw-top vial with O-ring (Sarstedt vial). Store specimens refrigerated up to 5 days or store frozen until shipped for testing. Ship frozen on dry ice or with freezer packs.

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.


Patient Criteria:

Appropriate clinical symptoms with known exposure to Amblyomma americanum (Lone Star) tick in Canada OR travel to eastern, southeastern or south-central United States. The symptoms of infection with Ehrlichia chaffeensis usually develop 1-2 weeks after being bitten by an infected tick. Symptoms may include fever, headache, chills, malaise, myalgia, nausea / vomiting / diarrhea, confusion, conjunctival injection and rash.

Accompanying Documentation:

Completed Requisition for Serological Testing for Selected Zoonotic Agents. If possible, include the clinical history and lab results performed at local or provincial laboratories.




Specimens may be subject to rejection if they are not the appropriate sample type, have insufficient volume, or are not accompanied by relevant patient information and travel history.


Methods and Interpretation of Results:

Commercially prepared IFA reagents. This is a semi-quantitative test for the detection of IgG antibodies to E. chaffeensis.  A four-fold or greater increase in IgG titre between two serum samples drawn 1 to 2 weeks apart and tested in parallel is considered presumptive evidence of a recent or current infection with E. chaffeensis. An IgG endpoint greater than 1:64 alone should not be relied on for a diagnosis of Ehrlichiosis.

Initiation of antibiotic treatment prior to testing may result in decreased antibody production which will affect the outcome of serological testing. However, if Ehrlichiosis is suspected based on clinical symptoms, treatment should be initiated.

Turnaround Time:

21 calendar days.

Phone #: (204) 789-7434 or (204) 789-7662
Fax: (204) 789-2082
  1. Dumler, J.S., Madigan, J.E., Pusteria, N., Bakken, J.S. 2007. Ehrlichiosis in humans: Epidemiology, clinical presentation, diagnosis and treatment. Clin. Inf. Dis. 45:S45-51.
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