Legionella pneumophila Antibody (Type 1), IgG by IFA
Ordering Recommendation
Semi-Quantitative Indirect Fluorescent Antibody
1-4 days  
New York DOH Approval Status
This test is New York DOH approved.
Submit With Order
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 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)
Component Test Code*Component Chart NameLOINC
0050376Legionella Type 1 By IFA, IgG9541-4
* 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.
  • Legionella pneumophila
  • Legionnaires Disease Testing