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HelpTest Code EHRC Ehrlichia chaffeensis (HME) Antibody, IgG, Serum
Reporting Name
Ehrlichia Chaffeensis (HME) Ab, IgGUseful 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
SerumSpecimen 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 |
Special Instructions
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 |
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)