RMSF GM
Spotted Fever Group Antibodies, IgG and IgM
EPIC Test Procedure Code: LAB2915
Synonyms:
Rocky Mountain Spotted Fever, IgG + IgM
Performing Lab:
Referral Laboratory
Container Type:
Red top or serum gel tube
Specimen Type:
Serum
Preferred Volume:
0.4 mL
Minimum Volume:
0.2 mL (Note: This volume does not allow for repeat testing.)
Store and Transport:
Room Temperature
Stability:
Frozen - 14 days (freeze/thaw cycles: stable x3)
Refrigerated - 14 days
Room temperature - 14 days
Unacceptable Condition:
Samples that are lipemic, hemolyzed or have bacterial contamination will be rejected.
Limitations:
This test is preferred for the acute or convalescent phase of disease. Acute and convalescent titers are often necessary. The CDC does not use IgM results for routine diagnostic testing of Rocky Mountain Spotted Fever, as the response may not be specific for the agent (resulting in false positives) and the IgM response may be persistent from past infection.
CPT Codes:
- 86757 - Rocky Mtn Spotted Fever IgM (EAP 30021018)
- 86757 - Rocky Mtn Spotted Fever IgG (EAP 30021017)
Method:
Semi-quantitative indirect fluorescent antibody (IFA)
Clinical Significance:
The test is useful in the diagnosis of spotted fever group rickettsial infections. Antibody reactivity to Rickettsia rickettsii antigen should be considered Spotted Fever group reactive. Other organisms within the group include R. akari, R. conorrii, R. australis and R. sibirica. This test is preferred for the acute or convalescent phase of disease. Acute and convalescent titers are often necessary. IgG serum endpoint titer of ≥1:64 is suggestive of infection at an unknown time and may be a sign of either past infection or early response to a recent infection. IgM titer of ≥1:64 is regarded as probable evidence of recent or ongoing infection. A four-fold or greater increase in titer between two serum samples drawn 1-2 weeks apart and tested in parallel is the best serologic indicator of a recent rickettsial infection.