ARUP's Laboratory Test Directory

Rickettsia rickettsii (Rocky Mountain Spotted Fever) Antibody, IgM : 0050372

Mnemonic: RMSF M

Methodology: Semi-Quantitative Indirect Fluorescent Antibody
Performed: Mon-Fri
Reported: 1-5 days
Specimen Required: Collect: Serum separator tube.

Specimen Preparation: Separate serum from cells ASAP or within 2 hours of collection. Transfer 1 mL serum to an ARUP Standard Transport Tube. (Min: 0.1 mL) Parallel testing is preferred and convalescent specimens must be received within 30 days from receipt of the acute specimens. Mark specimens plainly as acute or convalescent.

Storage/Transport Temperature: Refrigerated.

Unacceptable Conditions: Contaminated, hemolyzed, or severely lipemic specimens.

Stability (collection to initiation of testing): After separation from cells: Ambient: 48 hours; Refrigerated: 2 weeks; Frozen: 1 year (avoid repeated freeze/thaw cycles)
Reference Interval:
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 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 Code(s): 86757
Cross References: Rocky Mountain Spotted Fever Antibody (Rickettsia rickettsii (Rocky Mountain Spotted Fever) Antibody, IgM)