Assay Sheet

 

Test ID

5100 Legionella pneumophila PCR

CPT Code

87541

Clinical Utility

Legionella pneumophila is increasingly recognized as an important pathogen causing both community acquired pneumonia and nosocomial pneumonia. The mortality rate can be lowered if the disease is diagnosed rapidly and appropriate antimicrobial therapy is instituted. 

Laboratory diagnosis is important since pneumonia caused by L. pneumophila is clinically indistinguishable from other pneumonias. A molecular method such as PCR is a useful diagnostic tool since it is more rapid than culture and does not depend on growth of a fastidious organism. PCR is utilized for detection of L. pneumophila in lower respiratory tract specimens such as BAL and sputum, providing early, definitive diagnosis of infection. Moreover, the advantage of PCR includes its ability to detect all L. pneumophila serogroups which cause 80-90% of all Legionella infections. 

Procedure

Extraction of L. pneumophila DNA from respiratory specimens followed by amplification and detection of known L. pneumophila strains using real-time, qualitative PCR. An internal control is added to ensure the extraction was performed correctly and the PCR reaction was not inhibited.

Specimen type & specimen handling

Bronchial Lavage/Bronchial Wash: 2 mls collected in a sterile, screw top tube. Ship at ambient temperature Monday thru Friday. Specimen must be received within 96 hrs of collection.

Sputum: 2 mls collected in a sterile container, then transferred to sterile, screw top tube for shipment. Ship at ambient temperature Monday thru Friday. Specimen must be received within 96 hrs of collection.

Throat Gargle: 2 mls collected in a sterile container then transferred to sterile, screw top tube for shipment. Ship at ambient temperature Monday thru Friday. Specimen must be received within 96 hrs of collection.

Upper respiratory aspirate (NP aspirate, nasal aspirate/wash, tracheal aspirate, etc.): 2 mls collected in a sterile, screw top tube. Ship at ambient temperature Monday thru Friday. Specimen must be received within 96 hrs of collection.

Upper respiratory swab (NP swab, throat swab): Sterile swab placed in 2 ml sterile saline, M4, or viral transport media in a sterile, screw top tube.  Do not use calcium alginate swab or wood shafted swab.  Ship at ambient temperature Monday thru Friday.  Specimen must be received within 96 hrs of collection.

All suction-type collection devices are inappropriate for specimen transport. Transfer specimen into sterile, leak proof tube for transport.

Call ViraCor for authorization prior to sending any specimen type other than those listed above.  

If another specimen type has received authorization for testing the following comment will appear in the final report: "The clinical utility of this result has not yet been demonstrated in the peer reviewed literature and is therefore unknown."

Causes for rejection

Wood shafted swab, calcium alginate swab

Call ViraCor at 800-305-5198 if specimen is greater than 96 hrs old

Specimen types other than those listed above that were sent without prior authorization

Specificity

The Legionella pneumophila PCR assay was tested for cross reactivity against Bordetella pertussis, Bordetella parapertussis, Bordetella bronchiseptica, all relevant species of Chlamydophila, all relevant strains of Mycoplasma pneumoniae, Legionella anisa, Legionella dumoffii, Leginella feeleii, Legionella longbeachae, Legionella maceachernii, Legionella micdadei,  as well as human herpes viruses, polyoma viruses, hepatitis viruses, adenoviruses, parvovirus B19, Pneumocystis jirovecii and Toxoplasma gondii with no cross reactivity noted.

Assay Range

Qualitative results (Positive/Not Detected)

Turnaround Time

Same day (within 12 to 18 hours of receiving specimen), Monday through Saturday

Shipping

Ship Monday through Friday. Friday shipments must be labeled for Saturday delivery. All specimens must be labeled with patient's name and collection date. Multiple tests can be run on one specimen.

Ship specimens FedEx Priority Overnight to:

ViraCor Laboratories, 1001 NW Technology Dr, Lee's Summit, MO 64086

The CPT codes provided are based on ViraCor's interpretation of the American Medical Association's Current Procedural Terminology (CPT) codes and are provided for informational purposes only. CPT coding is the sole responsibility of the billing party. Questions regarding coding should be addressed to your local Medicare carrier. ViraCor assumes no responsibility for billing errors due to reliance on the CPT codes illustrated in this material. PCR tests are performed pursuant to a license agreement with Roche Molecular Systems, Inc. This assay was developed and the performance characteristics were determined at ViraCor Laboratories. This test is performed in a CLIA certified laboratory. FDA approval is not required for the performance of this test.

1009 V1

Pathogen Overview

 

About Legionella pneumophila

Legionnaires' disease (LD) is caused by Legionella pneumophila, a bacterial species which belongs to the family Legionellaceae. This family now includes 48 species and over 70 serogroups. Approximately half of these bacterial species have been implicated in human disease. Legionella species are small (0.3 to 0.9 μm in width and approximately 2 μm in length), faintly staining Gram-negative rods with polar flagella. Legionella is a fastidious organism and does not grow anaerobically or on standard media. L. pneumophila is responsible for approximately 90% of infections.  Fifteen serogroups of L. pneumophila have been identified, with serogroups 1, 4, and 6 being the primary causes of human disease. Serogroup 1 is thought to be responsible for 80% of the reported cases of LD caused by L. pneumophila. The bacteria got its name in 1976, when over 200 attendees of a Philadelphia convention of the American Legion suffered from an outbreak of this disease. Each year, between 8,000 and 18,000 people are hospitalized with Legionnaires' disease in the United States.

Legionella  Clinical Manifestations

Transmission of Legionella bacteria is thought to occur through inhalation of aerosolized mist from water sources contaminated with either the bacterium or amebic cells infected with the bacterium. Direct inhalation is the most likely method of transmission. Legionella species infect human macrophages and monocytes, and intracellular replication of the bacterium is observed within these cells in the alveoli.  The incubation period of LD is from two to ten days.  The patient may feel tired and weak for several days.  Most patients who are admitted to the hospital develop high fever often greater than 39.5°C (103°F). Cough, often accompanied by mucous production, can be the first sign of a lung infection. Gastrointestinal manifestations are common, with diarrhea being the most distinctive symptom.  Many patients have nausea, vomiting, and stomach discomfort.  Other common symptoms include headaches, muscle aches, chest pain, and shortness of breath. The most common risk factors include smoking, chronic lung disease, such as emphysema, diabetes, cancer, and age.  The most intense risk factor is immunosuppression as a result of HIV/AIDS or the administration of immunosuppressive drugs and corticosteroids. In response to Legionella infection, activated T cells produce lymphokines that stimulate increased antimicrobial activity of macrophages. This cell-mediated activation is key to halting the intracellular growth of Legionella. The significant role of cellular immunity explains why Legionella are observed more frequently in immunocompromised patients. Left untreated, Legionella infections may cause several life-threatening conditions, including respiratory failure, acute kidney failure, and septic shock.

Legionella Laboratory Diagnosis

Several laboratory tests can be used to detect the Legionella bacteria within the body. Traditionally, culture and serological tests have been utilized. However, culture is relatively insensitive for acute diagnosis and requires a long incubation period. Additionally, definitive diagnosis with serology requires seroconversion documented by paired specimens obtained 4 to 8 weeks apart. Currently, the most commonly used laboratory test for diagnosis is the urinary antigen test, which detects Legionella bacteria from a urine specimen. The persistence of antigen secretion in patients who are on antibiotic therapy increases the usefulness of this method. Recently, PCR has been utilized for detection of Legionella in urine, serum, and BAL, providing early, definitive diagnosis of infection. Moreover, the advantage of PCR includes its ability to detect all L. pneumophila serogroups.

Legionella Treatment

A delay in treatment significantly increases the risk of mortality. Therefore, empiric anti-Legionella therapy is often included in the regimen for severe community-acquired pneumonia and in specific cases of nosocomial pneumonia. Historically, erythromycin was used for L. pneumophila infection, but doxycycline, azithromycin, macrolides, and quinolones have proven more effective against LD.  The majority of healthy hosts exhibit clinical response to treatment within 3 to 5 days.

Selected References

Amsden GW. Treatment of Legionnaires' disease. Drugs. 2005;65(5):605-614.

Cunha BA. Hypophosphatemia: diagnostic significance in Legionnaires' disease. Am J Med. 2006;119(7):e5-6.

Cunha BA. The atypical pneumonias: clinical diagnosis and importance. Clin Microbiol Infect. 2006;12 Suppl 3:12-24.

Cunha BA. Legionella pneumonia: The value of clinical and laboratory findings. J Respir Dis. 2005;26:459-60.

Den Boer JW, Yzerman EP. Diagnosis of Legionella infection in Legionnaires' disease. Eur J Clin Microbiol Infect Dis. 2004;23(12):871-878.

Helbig JH, Engelstadter T, Maiwald M, et al. Diagnostic relevance of the detection of Legionella DNA in urine samples by the polymerase chain reaction. Eur J Clin Microbiol Infect Dis. 1999;18(10):716-722.

Kashuba AD, Ballow CH. Legionella urinary antigen testing: potential impact on diagnosis and antibiotic therapy. Diagn Microbiol Infect Dis. 1996;24(3):129-139.

Nolte FS. Molecular Diagnostics for Detection of Bacterial and Viral Pathogens in Community-Acquired

Pneumonia. Clin Infect Dis. 2008;47:S123-S126.

Schneeberger PM, Dorigo-Zetsma JW, van der Zee A, van Bon M, van Opstal JL. Diagnosis of atypical pathogens in patients hospitalized with community-acquired respiratory infection. Scand J Infect Dis. 2004;36(4):269-273.

Thibodeau KP, Viera AJ.  Atypical Pathogens and Challenges in Community-Acquired Pneumonia. American Family Physician. 2004;69(7):1699-1706.