Interpretation

Anaplasma phagocytophilum:

A positive result of an immunofluorescence assay (IFA) test (titer ≥1:64) suggests current or previous infection with human granulocytic ehrlichiosis (anaplasmosis). 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 EPCRB / Ehrlichia/Anaplasma, Molecular Detection, PCR, Blood).

Ehrlichia chaffeensis:

A positive IFA 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.

Babesia microti:

A positive result of an indirect fluorescent antibody test (titer ≥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 1:2560.