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Test Code EHRL Ehrlichia/Anaplasma, Molecular Detection, PCR, Blood

Reporting Name

Ehrlichia/Anaplasma PCR, B

Useful For

Evaluating patients suspected of acute anaplasmosis or ehrlichiosis

Performing Laboratory

Mayo Medical Laboratories in Rochester

Specimen Type

Whole Blood EDTA


Specimen Required


Container/Tube: Lavender top (EDTA)

Specimen Volume: 1 mL


Specimen Minimum Volume

0.3 mL

Specimen Stability Information

Specimen Type Temperature Time
Whole Blood EDTA Refrigerated (preferred) 7 days
  Frozen  7 days

Reference Values

Negative

Day(s) and Time(s) Performed

Monday through Saturday; Varies

Test Classification

This test was developed and its performance characteristics 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

87798 x 4

LOINC Code Information

Test ID Test Order Name Order LOINC Value
EHRL Ehrlichia/Anaplasma PCR, B In Process

 

Result ID Test Result Name Result LOINC Value
84319 Anaplasma phagocytophilum 30039-2
23663 Ehrlichia chaffeensis 27994-3
23664 Ehrlichia ewingii/canis 48865-0
32010 Ehrlichia muris-like 48866-8

Clinical Information

Ehrlichiosis and anaplasmosis are a group of emerging zoonotic tick-borne infections caused by Ehrlichia and Anaplasma species, respectively. These obligate intracellular, gram-negative rickettsial organisms infect leukocytes and cause a potentially serious febrile illness in humans.

 

Human granulocytic anaplasmosis (HA) is caused by Anaplasma phagocytophilum, which is transmitted through the bite of an infected Ixodes species tick. The epidemiology of this infection in the United States is very much like that of Lyme disease (caused by Borrelia burgdorferi) and babesiosis (caused primarily by Babesia microti), which all have the same tick vector. HA is most prevalent in the upper Midwest and in other areas of the United States that are endemic for Lyme disease.

 

Human monocytic ehrlichiosis (HE) is caused by Ehrlichia chaffeensis, which is transmitted by the Lone Star tick, Amblyomma americanum. Most cases of HE have been reported from the southeastern and south-central regions of the United States. E ewingii, the known cause of canine granulocytic ehrlichiosis, can occasionally cause an HE-like illness in humans. Clinical features and laboratory abnormalities are similar to those of E chaffeensis infection, and antibodies to E ewingii cross-react with current serologic assays for detection of antibodies to E chaffeensis.

 

Most recently, Mayo Medical Laboratories detected a new species of Ehrlichia in patients with exposure to ticks in Wisconsin and Minnesota. This organism is most closely related to E muris and has therefore been referred to as the E muris-like agent or EMLA. The name E muris eauclairensis has recently been proposed after the city in which the first case was described. E muris eauclairensis causes a similar disease to ehrlichiosis due to E chaffeensis and E ewingii, and may cause more severe disease in immunocompromised hosts.

 

Most cases of anaplasmosis and ehrlichiosis are subclinical or mild, but infection can be severe and life-threatening in some individuals. Fever, fatigue, malaise, headache, and other "flu-like" symptoms, including myalgias, arthralgias, and nausea, occur most commonly. Central nervous system involvement can result in seizures and coma.

 

Diagnosis may be difficult since the patient's clinical course is often mild and nonspecific. This symptom complex is easily confused with other illnesses such as influenza, or other tick-borne zoonoses such as Lyme disease, babesiosis, and Rocky Mountain spotted fever. Clues to the diagnosis of ehrlichiosis in an acutely febrile patient after tick exposure include laboratory findings of leukopenia or thrombocytopenia and elevated serum aminotransferase levels. However, while these abnormal laboratory findings are frequently seen, they are not specific. Rarely, intra-granulocytic or monocytic morulae may be observed on peripheral blood smear, but this is not a reliable means of diagnosing cases of human ehrlichiosis or anaplasmosis.

 

Definitive diagnosis is usually accomplished through PCR and serologic methods. Serologic testing is done primarily for confirmatory purposes, by demonstrating a 4-fold rise or fall in specific antibody titers to Ehrlichia species or Anaplasma antigens. There is not currently a commercially available specific serologic test for E muris eauclairensis, but cross-reactivity with the other Ehrlichia species by serology may be detected.

 

PCR techniques allow direct detection of pathogen-specific DNA from patients' whole blood and is the preferred method for detection during the acute phase of illness. The Mayo PCR assay is capable of detecting and differentiating A phagocytophilum, E chaffeensis, E ewingii, and E muris eauclairensis.

 

It is important to note that concurrent infection with A phagocytophilum, Borrelia burgdorferi, and Babesia microti is not uncommon as these organisms share the same Ixodes tick vector, and additional testing for these pathogens may be indicated.

Interpretation

Positive results indicate presence of specific DNA from Ehrlichia chaffeensis, E ewingii, E muris eauclairensis organism, or Anaplasma phagocytophilum and support the diagnosis of ehrlichiosis or anaplasmosis.

 

Negative results indicate absence of detectable DNA from any of these 4 pathogens in specimens, but do not exclude the presence of these organisms or active or recent disease.

 

Since DNA of E ewingii is indistinguishable from that of E canis by this rapid PCR assay, a positive result for E ewingii/canis indicates the presence of DNA from either of these 2 organisms.

Clinical Reference

1. Bakken JS, Dunler JS: Human granulocytic ehrlichiosis. Clin Infect Dis 2000 Aug;31(2):554-560

2. Dunler JS, Bakken JS: Human ehrlichioses: newly recognized infections transmitted by ticks. Ann Rev Med 1998;49:201-213

3. Krause PJ, McKay K, Thompson CA, et al: Disease-specific diagnosis of coinfecting tickborne zoonoses: babesiosis, human granulocytic ehrlichiosis, and Lyme disease. Clin Infect Dis 1999 May 1;34(9):1184-1191

4. McQuiston JH, Paddock CD, Holman RC, Childs JE: The human ehrlichioses in the United States. Emerging Infect Dis 1999 Sept-Oct;5(5):635-642

5. Pritt BS, Sloan LM, Johnson DK, et al: Emergence of a new pathogenic Ehrlichia species, Wisconsin and Minnesota, 2009. N Engl J Med 2011 Aug 4;365(5):422-429

6. Johnson DK, Schiffman E, Davis JP, et al. Human infection with Ehrlichia muris-like Pathogen, United States, 2007-2013. Emerging Infect Dis 2015; 21(10):1794-99

Analytic Time

Same day/1 day

Reject Due To

Hemolysis

Mild OK; Gross OK

Lipemia

Mild OK; Gross reject

Icterus

NA

Other

Anticoagulants other than EDTA

Method Name

Real-Time Polymerase Chain Reaction (PCR)/DNA Probe Hybridization

Forms

If not ordering electronically, complete, print, and send a Microbiology Test Request Form (T244) with the specimen (http://www.mayomedicallaboratories.com/it-mmfiles/microbiology_test_request_form.pdf).