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Test Code LABHMEIG Ehrlichia chaffeensis (HME) Antibody, IgG, Serum

Additional Codes

 

Test Name in EPIC EPIC Test Code Mnemonic Mayo Test ID
EHRLICH CHAFFEENSIS AB,
IGG		 LABHMEIG EHRC EHRC

 

Reporting Name

Ehrlichia Chaffeensis (HME) Ab, IgG

Useful For

An adjunct in the diagnosis of ehrlichiosis

 

Seroepidemiological surveys of the prevalence of the infection in certain populations

Testing Algorithm

For more information see Acute Tick-Borne Disease Testing Algorithm

Method Name

Immunofluorescence Assay (IFA)

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Specimen Type

Serum


Specimen Required


Supplies: Sarstedt Aliquot Tube, 5 mL (T914)

Collection Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Submission Container/Tube: Plastic vial

Specimen Volume: 0.5 mL

Collection Instructions: Centrifuge and aliquot serum into a plastic vial.


Specimen Minimum Volume

0.4 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Refrigerated (preferred) 14 days
  Frozen  14 days

Reject Due To

Gross hemolysis Reject
Gross lipemia Reject
Gross icterus Reject
Heat-inactivated specimen Reject

Reference Values

<1:64

Reference values apply to all ages.

Day(s) Performed

Monday through Friday

CPT Code Information

86666

LOINC Code Information

Test ID Test Order Name Order LOINC Value
EHRC Ehrlichia Chaffeensis (HME) Ab, IgG 47405-6

 

Result ID Test Result Name Result LOINC Value
81478 Ehrlichia Chaffeensis (HME) Ab, IgG 47405-6

Test Classification

This test was developed using an analyte specific reagent. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

Clinical Information

Ehrlichia chaffeensis is an intracellular rickettsia-like bacterium that preferentially infects monocytes and is sequestered in parasitophorous vacuoles referred to as morulae. Infections with E chaffeensis are also referred to as human monocytotropic ehrlichiosis (HME). E chaffeensis is transmitted by Amblyomma species ticks, which are found throughout the Southeastern and South-central United States.

 

Many cases of HME are subclinical or mild, however, the infection can be severe and life-threatening, particularly in immunosuppressed individuals. Reported mortality rates range from 2% to 3%. Fever, fatigue, malaise, headache, and other "flu-like" symptoms occur most commonly. Leukopenia, thrombocytopenia, and elevated hepatic transaminases are frequent laboratory findings.

Interpretation

A positive immunofluorescence assay result (titer ≥1:64) suggests current or previous infection. In general, the higher the titer, the more likely the patient has an active infection. Four-fold rises in titer also indicate active infection.

 

Previous episodes of ehrlichiosis may produce a positive serology result although antibody levels decline significantly during the year following infection.

Cautions

Serology results for IgG may be negative during the acute phase of infection (<7 days post-symptom onset), during which time detection using targeted nucleic acid amplification testing (eg, polymerase chain reaction) is recommended.

 

Detectable IgG-class antibodies typically appear within 7 to 10 days post-symptom onset.

 

IgG-class antibodies may remain detectable for months to years following prior infection. Therefore, a single time point-positive titer needs to be interpreted alongside other findings to differentiate recent versus past infection.

 

Other members of the Ehrlichia genus (eg, Ehrlichia ewingii) may not be detected by this assay.

Method Description

The patient's serum is diluted and is placed in microscopic slide wells that have been coated with Ehrlichia chaffeensis-infected cells. After incubation, the slides are washed and a fluorescein-isothiocyanate conjugate is added to each well. The slides are then read using a fluorescence microscope and significant fluorescent staining of intracellular organisms constitutes a positive reaction.(Dumler JS, Asanovich KM, Bakken JS, Richter P, Kimsey R, Madigan JE. Serologic cross-reactions among Ehrlichia equi, Ehrlichia phagocytophila, and human granulocytic Ehrlichia. J Clin Microbiol. 1995;33[5]:1098-1103; Pancholi P, Kolbert CP, Mitchell PD, et al. Ixodes dammini as a potential vector of human granulocytic ehrlichiosis. J Infect Dis. 1995;172[4]:1007-1012; Dawson JE, Fishbein DB, Eng TR, Redus MA, Green NR. Diagnosis of human ehrlichiosis with the indirect fluorescent antibody test: kinetics and specificity. J Infect Dis. 1990;162[1]:91-95; package insert: Ehrlichia chaffeensis IFA IgG. DiaSorin Molecular; 08/2016)

Report Available

Same day/1 to 3 days

Specimen Retention Time

14 days

Forms

If not ordering electronically, complete, print, and send Infectious Disease Serology Test Request (T916) with the specimen.