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HelpTest Code LEGRP Legionella species, Molecular Detection, PCR, Varies
Reporting Name
Legionella PCRUseful For
Sensitive and rapid diagnosis of pneumonia caused by Legionella species
The assay is not recommended as a test of cure because bacteria nucleic acids may persist after successful treatment.
Method Name
Rapid Polymerase Chain Reaction (PCR)
Performing Laboratory
Mayo Clinic Laboratories in Rochester
Specimen Type
VariesNecessary Information
Specimen source is required.
Specimen Required
The high sensitivity of amplification by polymerase chain reaction requires the specimen to be processed in an environment in which contamination of the specimen by Legionella DNA is unlikely.
Specimen Type: Lower respiratory
Sources: Bronchoalveolar lavage, bronchial aspirate/brushing/lavage/washing, tracheal/endotracheal secretions/aspirate, sputum
Container/Tube: Sterile container
Specimen Volume: 1 mL
Specimen Type: Fresh tissue or biopsy
Sources: Lung, pleura, heart valve, pericardium
Container/Tube: Sterile container
Specimen Volume: Entire collection or 5 mm(3) - approximately the size of a pencil eraser
Collection Instructions: Aseptically collect a 1 to 2 cm(3) piece of tissue whenever possible
Specimen type: Fluid
Sources: Pericardial, pleural, chest, chest tube drainage, thoracentesis, empyema
Container/Tube: Sterile container
Specimen Volume: 1 mL
Specimen Minimum Volume
See Specimen Required
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Varies | Refrigerated (preferred) | 7 days | |
| Frozen | 7 days |
Reject Due To
| Tissue in formalin, formaldehyde, or acetone Formalin-fixed paraffin-embedded (FFPE) block |
Reject |
Reference Values
Not applicable
Day(s) Performed
Monday through Sunday
CPT Code Information
87801
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| LEGRP | Legionella PCR | 5020-3 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| SRC57 | Specimen Source | 31208-2 |
| 29515 | Legionella PCR, Result | 5020-3 |
Clinical Information
Legionnaires disease was first recognized during a pneumonia outbreak at the Legionnaires convention in Philadelphia in 1976. Investigators with the Centers for Disease Control and Prevention isolated a novel, gram-negative bacillus, later named Legionella pneumophila. It is now widely recognized that L pneumophila (and other members of the genus Legionella) cause Legionnaires disease.
Interpretation
A positive polymerase chain reaction (PCR) result for the presence of a specific sequence found within the Legionella 5S ribosomal RNA gene indicates the presence of a Legionella species DNA, which may be due to Legionella infection or environmental/water Legionella DNA in the specimen.
A negative PCR result indicates the absence of detectable Legionella DNA in the specimen but does not rule-out legionellosis as false-negative results may occur due to inhibition of PCR, sequence variability underlying the primers and probes, or the presence of Legionella species in quantities less than the limit of detection of the assay.
Cautions
This assay does not differentiate between the Legionella species. False-positive results are theoretically possible if patient specimens are contaminated with Legionella DNA, which may occur since Legionella species are environmental organisms present in aquatic environments.
The following uncommonly encountered species of Legionella are not detected by this assay: Legionella anisa,  Legionella feeleii,  Legionella maceachernii,  Legionella parisiensis, and  Legionella sainthelensi.
Method Description
This method employs a target-specific detection system using fluorescent resonance energy transfer (FRET) hybridization probes designed for a specific sequence found within the Legionella 5S ribosomal RNA gene. The LightCycler (LC) instrument amplifies and monitors target nucleic acid sequences by fluorescence during polymerase chain rection (PCR) cycling. This is an automated PCR system that can rapidly detect amplified product development through stringent air-controlled temperature cycling and capillary cuvettes. The detection of amplified products is based on the FRET principle. For FRET product detection, a hybridization probe with a donor fluorophore, fluorescein, on the 3' end is excited by an external light source, which emits light that is absorbed by a second hybridization probed with an acceptor fluorophore, LC-Ted 640, on the 5' end. The acceptor fluorophore then emits light of a different wavelength that can be measured with a signal that is proportional to the amount of specific PCR product. The detection process is completed in under an hour using a closed tube system.(Cunningham SA, Sloan LM, Uhl JA, et al: Validation of a real-time PCR assay for the detection of Legionella species in respiratory samples. Abstracts of the Annual Meeting of the Association for Molecular Pathology, 2009 General Meeting, Nov. 19-22, 2009; Rucinski SL, Murphy MP, Kies KD, Cunningham SA, Schuetz AN, Patel R. Eight years of clinical Legionella PCR testing illustrates a seasonal pattern. J Infect Dis. 2018 Jul 13;218(4):669-670. doi: 10.1093/infdis/jiy201)