Ordering Recommendation

Provide retrospective evidence of suspected Legionella pneumophila infection.




Semi-Quantitative Indirect Fluorescent Antibody




1-4 days

New York DOH Approval Status

This test is New York DOH approved.

Specimen Required

Patient Preparation

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


Unacceptable Conditions

Contaminated, hemolyzed, or severely lipemic specimens.


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 1-6 IgG antibody detected.
1:128 Equivocal - Questionable presence of Legionella pneumophila Type 1-6 IgG antibody detected. Repeat testing in 10-14 days may be helpful.
1:256 or greater Positive -  Presence of Legionella pneumophila Type 1-6 IgG antibody detected, suggestive of current or past infection.

Interpretive Data

Seroconversion between acute and convalescent sera is considered strong evidence of recent infection.  The best evidence for infection is a significant change on two appropriately timed specimens where both tests are done in the same laboratory at the same time.  This assay may detect infection by any of the serotypes 1-6.  The CDC and many state health laboratories recommend testing only for antibody to Legionella pneumophila Type 1.  For equivocal or positive IFA results, the CDC protocol suggests follow-up testing for Legionella pneumophila antibody Type 1.

Compliance Category



Hotline History


CPT Codes



Component Test Code* Component Chart Name LOINC
0050365 Legionella Pneumophila 1-6,IgG 53770-4
* Component test codes cannot be used to order tests. The information provided here is not sufficient for interface builds; for a complete test mix, please click the sidebar link to access the Interface Map.


  • L pneumophila IgG
  • L pneumophila Types 1-6 Ab
  • Legionella pneumophila IgG antibody
  • Legionnaires Disease Testing
Legionella pneumophila Antibody (Types 1-6), IgG by IFA