ARUP's Laboratory Test Directory

0050371: Rickettsia rickettsii (Rocky Mountain Spotted Fever) Antibodies, IgG & IgM by ELISA

Test Mnemonic: RMSF G/M
Methodology: Indirect Immunofluorescence Assay

Performed: Mon-Fri

Reported: 1-5 days

Specimen Required:  
Collect: One 4 mL SST.

Transport: 1 mL serum at 2-8°C. (Min: 0.5 mL) Submit specimen in an ARUP Standard Transport Tube.

Pediatric Collection/Transport: 0.3 mL serum at 2-8°C.

Remarks: Separate serum from cells ASAP. Acute and convalescent specimens must be labeled as such; parallel testing is preferred and convalescent specimens must be received within 30 days from receipt of the acute specimens. Please mark specimen plainly as "acute" or "convalescent."

Unacceptable Conditions: Severely lipemic, contaminated, or hemolyzed specimens.

Stability: After separation from cells: Ambient: 2 days; Refrigerated: 2 weeks; Frozen: 1 year (avoid repeated freeze/thaw cycles)

Reference Interval:
 
Test Number Components Reference Interval
0050369Rickettsia rickettsii (Rocky Mountain Spotted Fever) Antibody, IgG Less than 1:64: Negative - No significant level of Rickettsia rickettsii Antibody, IgG detected.
1:64 - 1:128: Low Positive - Presence of Rickettsia rickettsii Antibody, IgG detected, suggestive of current or past infection.
1:256 or greater: Positive - Presence of Rickettsia rickettsii Antibody, IgG suggestive of recent or current infection.
0050372Rickettsia rickettsii (Rocky Mountain Spotted Fever) Antibody, IgM Less than 1:64: Negative - No significant level of Rickettsia rickettsii Antibody, IgM detected.
1:64 or greater: Positive - Presence of Rickettsia rickettsii Antibody, IgM detected, which may indicate a current or recent infection; however, low levels of IgM antibodies may occasionally persist for more than 12 months post-infection.
 

Interpretive Data:
The best evidence for current infection is a significant change on two appropriately timed specimens, where both tests are done in the same laboratory at the same time.

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.

Please refer to Statement A in the Compliance Statements section in the front of the Laboratory Test Directory.



CPT Code(s):
86757 RMSF IgG; 86757 RMSF IgM

 

 

 
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