Test Catalog

Test ID: EHBAP    
Ehrlichia/Babesia Antibody Panel, Immunofluorescence, Serum

Useful For Suggests clinical disorders or settings where the test may be helpful

As an adjunct in the diagnosis of infection with Anaplasma phagocytophilum, Ehrlichia chaffeensis or Babesia microti


Seroepidemiological surveys of the prevalence of the infection in certain populations

Testing Algorithm Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

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

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Anaplasma phagocytophilum:

Anaplasma phagocytophilum, an intracellular rickettsia-like bacterium, preferentially infects granulocytes and forms inclusion bodies, referred to as morulae. A phagocytophilum is transmitted by Ixodes species ticks, which also transmit Borrelia burgdorferi and Babesia species. Infection with A phagocytophilum is also referred to as human granulocytic anaplasmosis (HGA) and symptoms in otherwise healthy individuals are often mild and nonspecific, including fever, myalgia, arthralgia, and nausea. Clues to the diagnosis of anaplasmosis in a patient with an acute febrile illness after tick exposure include laboratory findings of leukopenia or thrombocytopenia and elevated liver enzymes. HGA is most prevalent in the upper Midwest and in other areas of the United States that are endemic for Lyme disease.


Ehrlichia chaffeensis:

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.


Babesia microti:

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.


Babesiosis is a zoonotic infection caused by the protozoan parasite Babesia microti. The infection is acquired by contact with Ixodes ticks carrying the parasite. The deer mouse is the animal reservoir, and overall, the epidemiology of this infection is much like that of Lyme disease. Babesiosis is most prevalent in the Northeast, upper Midwest, and Pacific coast of the United States.


Infectious forms (sporozoites) are injected during tick bites and the organism enters the vascular system where it infects red blood cells (RBC). In this intraerythrocytic stage it becomes disseminated throughout the reticuloendothelial system. Asexual reproduction occurs in RBC, and daughter cells (merozoites) are formed, which are liberated on rupture (hemolysis) of the RBC.


Most cases of babesiosis are probably subclinical or mild, but the infection can be severe and life threatening, especially in older or asplenic patients. Fever, fatigue, malaise, headache, and other flu-like symptoms occur most commonly. In the most severe cases, hemolysis, acute respiratory distress syndrome, and shock may develop. Patients may have hepatomegaly and splenomegaly.


A serologic test can be used as an adjunct in the diagnosis and follow-up of babesiosis, when infection is chronic or persistent, or in seroepidemiologic surveys of the prevalence of the infection in certain populations. Babesiosis is usually diagnosed by observing the organisms in infected RBC on Giemsa-stained thin blood films of smeared peripheral blood. Serology may also be useful if the parasitemia is too low to detect or if the infection has cleared naturally or following treatment.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.



Reference values apply to all ages.




Reference values apply to all ages.




Reference values apply to all ages.

Interpretation Provides information to assist in interpretation of the test results

Anaplasma phagocytophilum:

A positive result of an immunofluorescence assay (IFA) test (titer > or =1:64) suggests current or previous infection with human granulocytic ehrlichiosis. In general, the higher the titer, the more likely it is that the patient has an active infection.


Seroconversion may also be demonstrated by a significant increase in IFA titers.


During the acute phase of the infection, serologic tests are often nonreactive, polymerase chain reaction (PCR) testing is available to aid in the diagnosis of these cases (see EHRL / Ehrlichia/Anaplasma, Molecular Detection, PCR, Blood).


Ehrlichia chaffeensis:

A positive immunofluorescence assay (titer > or =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.


Babesia microti:

A positive result of an indirect fluorescent antibody test (titer > or =1:64) suggests current or previous infection with Babesia microti. In general, the higher the titer, the more likely it is that the patient has an active infection. Patients with documented infections have usually had titers ranging from 1:320 to 1:2,560.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

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


Anaplasma phagocytophilum:

Previous episodes of human granulocytic ehrlichiosis may produce a positive serologic result.


In rare instances, clinical evidence of infection may also be derived by direct microscopic examination of Giemsa- or Diff-Quik-stained peripheral blood buffy coat smears, which may reveal clusters of round, dark-purple stained, small dots or clusters of dots (morulae) in the cytoplasm of polymorphonuclear cells. However, this is a very insensitive method.



Ehrlichia chaffeensis:

Serology 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: PCR) 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.


Babesia microti:

Previous episodes of babesiosis may produce a positive serologic result.


In selected cases, documentation of infection may be attempted by animal inoculation or PCR methods (LBAB / Babesia species, Molecular Detection, PCR, Blood)

Clinical Reference Recommendations for in-depth reading of a clinical nature

Centers for Disease Control and Prevention: Tickborne Diseases of the United States: A Reference Manual for Health Care Providers. 4th ed. Department of Health and Human Services; 2017

Special Instructions Library of PDFs including pertinent information and forms related to the test