Assay Sheet

 

For in vitro diagnostic use

Test ID Code

5400 Legionella Urinary Antigen Test

CPT Code

87449

Clinical Utility

Legionella pneumophila is responsible for 80-90% of reported cases of Legionella infection with serogroup 1 accounting for greater than 70% of all legionellosis.

The BinaxNOW® Legionella Urinary Antigen Test is an in vitro rapid immunochromatographic assay for the qualitative detection of Legionella pneumophila serogroup 1 antigen (L. pneumophila serogroup 1 antigen) in urine specimens from patients with symptoms of pneumonia. It is intended to aid in the presumptive diagnosis of Legionella infection (Legionnaires' Disease) caused by L. pneumophila serogroup 1in conjunction with culture and other methods.

Procedure

The BinaxNOW® Legionella Urinary Antigen Test is an immunochromatographic membrane assay to detect Legionella pneumophila serogroup 1 soluble antigen in human urine.

Specimen type & specimen handling

Urine: 1 to 2 ml sample collected in a sterile urinalysis container. Transfer to a 15 ml sterile, screw-cap tube; Specimen should be stored refrigerated at 2 to 8°C or frozen and shipped with frozen gel packs for overnight delivery at ViraCor.

Causes for Rejection

• Specimens other than urine.
• Specimens that have been stored at ambient temperature for >24hours.
• Specimens that have been stored at 2 to 8°C for >14days.

Assay Limitations

The BinaxNOW® Legionella Urinary Antigen Test has been validated using urine samples only. Other samples (e.g., plasma, serum or other body fluids) that may contain Legionella antigen have not been evaluated. The test cannot be used on environmental samples (i.e. potable water).

This test will not detect infections caused by other L. pneumophila serogroups and by other Legionella species. A negative antigen result does not exclude infection with L. pneumophila serogroup 1. All laboratory findings should be used in conjunction with clinical findings to make an accurate diagnosis

Assay Range

Qualitative results(Positive/Not Detected)

Diagnonsis and Monitoring

Current methods for the laboratory detection of pneumonia caused by Legionella pneumophila require a respiratory specimen (e.g. expectorated sputum, bronchial washing, transtracheal aspirate, lung biopsy) or paired sera (acute and convalescent) for an accurate diagnosis. These techniques include Legionella culture, direct fluorescent antibody (DFA), DNA probe, and PCR.

Excretion of Legionella antigen in urine may vary depending on the individual patient. Antigen excretion may begin as early as 3 days after onset of symptoms and persist for up to 1 year afterwards. A positive BinaxNOW® Legionella Urinary Antigen Test result can occur due to current or past infection and therefore is not definitive for infection without other supporting evidence.

Turnaround Time

Same day (within 8 to 12 hours of specimen receipt), 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. A ViraCor test requisition form must accompany each 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. This test is performed at ViraCor Laboratories, a CLIA certified laboratory. The BinaxNOW® Legionella Urinary Antigen EIA is a product of Inverness Medical, Inc. BinaxNOW® is a registered trademark of Inverness Medical, Inc.

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.