Test ID: SFGP Spotted Fever Group Antibody, IgG and IgM, Serum
Reporting Name
Spotted Fever Group Ab, IgG, IgM, SUseful For
Aids in the diagnosis of spotted fever group rickettsial infections
Clinical Information
Species of Rickettsia are small (0.3-0.5 mcm x 1-2 mcm) obligately intracellular bacteria (Proteobacteria). They have a gram-negative cell wall structure. Rickettsia are found in arthropod hosts for at least part of their life cycle.
Rickettsial infections in the United States are caused by 2 major groups within the genus Rickettsia: spotted fever group and typhus fever group. The spotted fever group includes R rickettsii (Rocky Mountain spotted fever), R akari, R conorii (Boutonneuse fever), R australis (Queensland tick typhus), and R sibirica (North Asian tick typhus). The typhus fever group includes R typhi (murine typhus; endemic typhus) and R prowazekii (epidemic typhus).
R rickettsiae is the most common rickettsial species encountered in the United States and is transmitted through a tick vector (Dermacentor species or, less commonly, Rhipicephalus sanguineus). Following a 2- to 14-day incubation period, patients most commonly present with fever, chills, and myalgia. A maculopapular rash typically appears 2 to 5 days after fever onset, though approximately 10% of patients will not develop a rash. Antibodies to the spotted fever group agents are detectable within 7 to 10 days after illness onset. Demonstration of either 1) seroconversion or 2) a 4-fold change in IgG-specific antibody titers in acute and convalescent serum samples is consistent with acute or ongoing disease.
Interpretation
This test detects reactivity to the group-specific rickettsia. For example, antibody reactivity to the Rickettsia rickettsii will also react with other organisms within the spotted fever group.
IgG
≥1:256:
-Serum end point titers of ≥1:256 are considered presumptive evidence of recent or current infection by organisms of appropriate rickettsial antigen group.
<1:256 and ≥1:64:
-Single serum end point titers ≥1:64 and <1:256 are suggestive of infection at an undetermined time and may indicate either past infection or early response to a recent rickettsial infection.
-A 4-fold or greater increase in IgG titer between 2 serum specimens drawn 1 to 2 weeks apart and tested in parallel is considered presumptive evidence of a recent or current infection.
-In patients infected with organisms within the rickettsial groups, IgG antibody is generally detectable within 1 to 2 weeks of onset of symptoms, peaking within 1 to 2 months and declining thereafter. Following prompt antimicrobial treatment, titers generally decline below detectable levels within 8 to 11 months. With relapse, prior immunization, or delayed antibiotic treatment, IgG levels may remain elevated for more than a year postonset.
IgM
≥1:64:
-Titers of ≥1:64 are considered presumptive evidence of recent or current infection by organisms of appropriate rickettsial antigen group.
<1:64:
-Titers <1:64 suggest that the patient does not have an acute rickettsial infection.
-IgM class antibody is transiently detected within 1 to 2 weeks of onset of symptoms, usually declining rapidly within 3 months following prompt antibiotic treatment. These levels will also be elevated for an extended period with relapse, prior immunization, or delayed antibiotic treatment.
Testing Algorithm
See Acute Tick-Borne Disease Testing Algorithm in Special Instructions.
Report Available
Same day/1 to 3 daysDay(s) Performed
Monday through Friday
Clinical Reference
1. Walker DH, Bouyer DH: Rickettsia: In Manual of Clinical Microbiology. Eighth edition. Edited by PR Murray, EJ Baron, JH Jorgenson et al. Washington, DC, ASM Press, 2003, pp 1005-1014
2. Helmick C, Bernard K, D'Angelo L: Rocky Mountain spotted fever. Clinical laboratory and epidemiological features of 262 cases. J Clin Microbiol 1984;12:343-350
3. Centers for Disease Control and Prevention: Tickborne diseases of the United States. A Reference Manual for HealthCare Providers. First Edition 2013. Available at www.cdc.gov/lyme/resources/TickborneDiseases.pdf
Method Name
Immunofluorescence
Specimen Type
SerumSpecimen Required
Container/Tube:
Preferred: Serum gel
Acceptable: Red top
Specimen Volume: 0.5 mL
Specimen Minimum Volume
0.2 mL
Specimen Stability Information
Specimen Type | Temperature | Time | Special Container |
---|---|---|---|
Serum | Refrigerated (preferred) | 14 days | |
Frozen | 14 days |
Special Instructions
Reference Values
IgG: <1:64
IgM: <1:64
Reference values apply to all ages.
Test Classification
This test has been cleared, approved, or is exempt by the US Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.CPT Code Information
86757 x 2
LOINC Code Information
Test ID | Test Order Name | Order LOINC Value |
---|---|---|
SFGP | Spotted Fever Group Ab, IgG, IgM, S | 90260-1 |
Result ID | Test Result Name | Result LOINC Value |
---|---|---|
84342 | Spotted Fever Group Ab, IgG, S | 5313-2 |
84346 | Spotted Fever Group Ab, IgM, S | 5315-7 |
Forms
If not ordering electronically, complete, print, and send a Microbiology Test Request (T244) with the specimen.
mml-CNS-Infections, mml-Pediatric