Rickettsia rickettsii/typhi IgG Antibody

The  Rickettsia immunofluorescent assay (IFA) is designed to detect Rickettsia specific antibodies in human serum.  For diagnostic purposes, IFA test results should be used in conjunction with other data available to the physician.


The Rickettsia IFA assay is a “two-stage” sandwich assay, based upon an antigen-antibody complex formation in the following steps:

  1. Binding of anti-Rickettsia specific antibodies in human serum to fixed Rickettsia
  2. Binding of fluorescent-labeled anti-human IgG/IgM antibodies to the human anti– Rickettsia antibodies bound to Rickettsia on the slide. 
  3. Identifing green fluorescing Rickettsia organisms  with a fluorescent microscope. 

Result Interpretation

Reference Range

  • Rickettsia antibody titers IgG        <40

Clinical Significance

The Rickettsia immunofluorescent antibody test is used to detect antibodies to Rickettsia species in human serum. These species include R. ricketsii and R. typhi, known to cause Rocky Mountain Spotted Fever and Murine Typhus respectively. Titers rise during the first 2 to 4 weeks of illness and decline over 6 to 12 months. In patients with previously high titers, titers of <160 may indicate a resolving infection. If the IFA result is negative but the clinical symptoms are present, PCR testing is suggested.

Ordering Information

  • Specimen: Serum - minimum volume 0.5 ml
  • Container: SST (Serum Separator Tube) OR Leak-proof tube
  • Collection and Shipping Instructions: See Serum and Whole Blood Samples- Collection & Shipping Instructions [THIS WILL LINK TO THAT PAGE]

Test Offered

Test# 965 Rickettsia rickettsia/typhi IgG Antibody CPT Code 86757 x2
Rickettsia rickettsia/typhi IgG Antibody is part of the following Test Panels:
Test Panel# 995 Complete Rickettsia Panel