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UW Health SMPH
American Family Children's Hospital

UW Hospital and Clinics Lab Test Directory

Test Name: Legionella Ab

Test Code(s): MISC / RMISC

CPT Code(s): 86713

Methodology: Indirect Fluorescent Antibody

Clinical Significance: Used to support a diagnosis of Legionnaires disease retrospectively during the convalescent phase of illness.

Testing Site: Testing will be sent to an approved reference laboratory.

Days Performed: Once a week.

Turnaround Time: Routine: 2 - 7 days.


Specimen Requirements

Specimen: Blood

Collection Instructions: Acute and convalescent serum required. Collect acute serum during first week of illness and convalescent serum 3-6 weeks post onset for diagnostic testing.

Include date of onset of illness and whether specimen is acute or convalescent.

Collection Container: Preferred: Red top

Collection Volume: Preferred: 9 mL
Pediatrics: 3 mL

Sample Analyzed: Serum

Volume Required: Preferred: 1 mL
Pediatrics: 0.5 mL

Specimen Processing: Centrifuge. Transfer cell free serum to plastic vial. Refrigerate.

Specimen Transport: Transport specimen to UWHC Core Laboratory (B4/220). Transport with coolant pack if coming from outreach location.  


Interpretation

Reference Interval:

A titer equal to 1:128 on a single serum or an increase of less than four-fold in the titer between acute and convalescent sera is considered negative.

Test Limitations:

The only confirmed positive serology result is demonstration of a four-fold rise in titer greater than or equal to 1:128 between paired sera. Varying background levels of antibody in the general population make it difficult to support a diagnosis based on a single serum titer.

Additional Information:

Must include date of collection and date of onset of illness.

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