Legionella pneumophila Antibody (Type 1), IgG by IFA
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.
Submit With Order
ARUP Consult®
Disease Topics
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.

Hotline History
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 view this test within the Laboratory Test Directory found at www.aruplab.com
  • Legionella pneumophila
  • Legionnaires Disease Testing