FRANC - Clinical: Francisella Tularensis Antibody

Test Catalog

Test Name

Test ID: FRANC    
Francisella Tularensis Antibody

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

Tularemia antibody titers > or = to 1:40 are of diagnostic significance. However, titers in this range may also indicate previous infection.  Antibody begins to appear 2-3 week post-onset and generally peaks at approximately 5 weeks into the disease. With this delay in antibody appearance a second specimen will usually demonstrate a diagnostic four-fold rise in titer for patients with active disease.

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 Range:  <1:20

Interpretation Provides information to assist in interpretation of the test results

Interpretive Criteria:

<1:20 Negative

1:20 - 1:80 Equivocal

> or =1:160 Positive


In the presence of compatible symptoms, a Francisella tularensis antibody titer of 1:160 or greater in an acute specimen supports a presumptive diagnosis of tularemia. However, a titer > or =1:160 may also reflect past infection. An equivocal titer may be due to cross-reactive antibodies (Brucella, Yersinia, or Proteus OX19), past infection, or very recent infection. A four-fold rise in titer between acute and convalescent sera is required for definitive serologic diagnosis of tularemia.

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

Test may demonstrate cross reactivity with brucella, Proteus OX-19, and Yersinia species. Antibodies may be elevated many years after infection.