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Test Code EHRCP Ehrlichia Antibody Panel, Serum

Reporting Name

Ehrlichia Ab Panel

Useful For

As an adjunct in the diagnosis of ehrlichiosis

 

In seroepidemiological surveys of the prevalence of the infection in certain populations

Profile Information

Test ID Reporting Name Available Separately Always Performed
ANAP Anaplasma phagocytophilum Ab, IgG,S Yes Yes
EHRC Ehrlichia Chaffeensis (HME) Ab, IgG Yes Yes

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Specimen Type

Serum


Specimen Required


Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Specimen Volume: 0.5 mL


Specimen Minimum Volume

0.25 mL

Specimen Stability Information

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

Reference Values

ANAPLASMA PHAGOCYTOPHILUM

<1:64

Reference values apply to all ages.

 

EHRLICHIA CHAFFEENSIS

<1:64

Reference values apply to all ages.

Day(s) and Time(s) Performed

Monday through Friday; 9 a.m.

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 U.S. Food and Drug Administration.

CPT Code Information

86666 x 2

LOINC Code Information

Test ID Test Order Name Order LOINC Value
EHRCP Ehrlichia Ab Panel 77165-9

 

Result ID Test Result Name Result LOINC Value
81157 Anaplasma phagocytophilum Ab, IgG,S 23877-4
81478 Ehrlichia Chaffeensis (HME) Ab, IgG 47405-6

Testing Algorithm

See Acute Tick-Borne Disease Testing Algorithm in Special Instructions.

Clinical Information

ANAP:

Human granulocyte ehrlichiosis (HGE) is a zoonotic infection caused by a rickettsia-like agent. The infection is acquired by contact with Ixodes ticks carrying the HGE agent. The deer mouse is the animal reservoir and, overall, the epidemiology is very much like that of Lyme disease and babesiosis. HGE is most prevalent in the upper Midwest and in other areas of the United States that are endemic for Lyme disease. Since its first description in 1994, there have been approximately 50 cases of HGE described in the upper Midwest.

 

The cellular target in HGE cases is the neutrophil. The organisms exist in membrane-lined vacuoles within the cytoplasm of infected host cells. Ehrlichial inclusions, called morulae, contain variable numbers of organisms. Single organisms, wrapped in vacuolar membranes have also been observed in the cytoplasm. Ehrlichia species occur in small electron-dense and large electron-lucent forms, but a clear life cycle has not been elucidated.

 

Diagnosis of human ehrlichiosis has been difficult because the patient's clinical course is often mild and nonspecific, including fever, myalgias, arthralgias, and nausea. This is easily confused with other illnesses such as influenza or other tickborne zoonoses such as Lyme disease, babesiosis, and Rocky Mountain spotted fever. Clues to the diagnosis of ehrlichiosis in a patient with an acute febrile illness after tick exposure include laboratory findings of leukopenia or thrombocytopenia and elevated serum aminotransferase levels. However, these findings may also be present in patients with Lyme disease or babesiosis.

 

EHRC

Ehrlichiosis is an emerging zoonotic infection caused by obligate intracellular, gram-negative rickettsia that infects leukocytes.

 

Human monocytic ehrlichiosis (HME) is caused by Ehrlichia chaffeensis and is transmitted by the Lone Star tick, Amblyomma americanum. The deer is believed to be the animal reservoir and most cases of HME have been reported from the southeastern and south-central region of the United States.

 

Infectious forms are injected during tick bites and the organism enters the vascular system where it infects monocytes. It is sequestered in host-cell membrane-limited parasitophorous vacuoles known as morulae. These can be readily observed on Giemsa- or Wright-stained smears of peripheral blood from infected persons. Macrophages in organs of the reticuloendothelial system are also infected. Asexual reproduction occurs in WBCs and daughter cells are formed that are liberated upon cell rupture.

 

Ehrlichiosis is sometimes diagnosed by observing the organisms in infected WBCs on Giemsa-stained thin blood films of smeared peripheral blood (morulae). Serology may be useful if the morulae are not seen or if the infection has cleared naturally or following treatment.

 

Most cases of ehrlichiosis are probably subclinical or mild, but the infection can be severe and life-threatening; there is a 2% to 3% mortality rate. Fever, fatigue, malaise, headache, and other "flu-like" symptoms occur most commonly. Central nervous system involvement can result in seizures and coma. Leukopenia, thrombocytopenia, and elevated hepatic transaminases are frequent laboratory findings.

 

Serology may also be useful in the follow-up of documented cases of ehrlichiosis or when coinfection with other tick-transmitted organisms is suspected. In selected cases, documentation of infection may be attempted by PCR methods.

Interpretation

A positive immunofluorescence assay (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 although antibody levels decline significantly during the year following infection.

Cautions

Serology for IgG may be negative during the acute phase of infection but a diagnostic titer usually appears by the third week after onset. Previous episodes of ehrlichiosis may produce a positive serology although antibody levels decline significantly during the year following infection.

 

Performance characteristics have not been established for hemolyzed or lipemic specimens.

Clinical Reference

1. Bakken JS, Dumler JS, Chen SM, et al: Human granulocytic ehrlichiosis in the upper Midwest United States. A new species emerging? JAMA 1994;272:212-218

2. Fishbein DB, Dawson JE, Robinson LE: Human ehrlichiosis in the United States, 1985 to 1990. Ann Intern Med 1994;120:736-743

Analytic Time

Same day/1 day

Specimen Retention Time

14 days

Reject Due To

Hemolysis

Mild OK; Gross reject

Lipemia

Mild OK; Gross reject

Icterus

NA

Other

Heat-inactivated specimen

NY State Approved

Yes

Method Name

Immunofluorescence Assay (IFA)

Method Description

The patient's serum is diluted and is placed in microscopic slide wells that have been coated with Anaplasma phagocytophilum-infected cells and/or Ehrlichia chaffeenis-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, et al: Serologic cross-reactions among Ehrlichia equi, Ehrlichia phagcoytophilia, and human granulocytic ehrlichia. J Clin Microbiol 1995;33:1098-1103; Pancholi P, Kolbert CP, Mitchell PD, et al: Ixodes dammini as a potential vector of human granulocytic ehrlichiosis. J Infect Dis 1995;172:1007-1012) (Dawson JE, Fishbein DB, Eng TR, et al: Diagnosis of human ehrlichiosis with the indirect fluorescent antibody test: kinetics and specificity. J Infect Dis 1990;162:91-95)