ARUP's Laboratory Test Directory

Legionella pneumophila Antibody (Type 1), IgG by IFA : 0050376

Mnemonic: LEGAB IFA

Methodology: Semi-Quantitative Indirect Fluorescent Antibody
Performed: Mon-Fri
Reported: 1-4 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:
< 1:128  Negative - No significant level of Legionella pneumophila Type 1 IgG antibody detected.
1:128  Equivocal - Questionable presence of Legionella pneumophila Type 1 IgG antibody detected. Repeat testing in 10-14 days may be helpful.
1:256 or greater  Positive -  Presence of Legionella pneumophila Type 1 IgG detected, suggestive of current or past infection.
Interpretive Data: The CDC and many state health laboratories recommend testing only for antibody to Legionella pneumophila Type 1. 

A fourfold rise in titer greater than 1:128 from the acute to the convalescent phase provides evidence of a recent infection with Legionella.  A standing or single titer greater than or equal to 1:256 suggests past exposure or infection, but is inconclusive for diagnosis.  Single titers of less than 1:256 are not considered evidence of infection.  Diagnosis of acute infection can only be made with a fourfold or greater rise in titer between acute and convalescent specimens.
CPT Code(s): 86713