The Binax NOW^® Legionella Urinary Antigen Test is an in vitro rapid immunochromatographic assay for the qualitative detection of Legionella pneumonia 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. pneumophilia serogroup 1 in conjunction with culture and other methods.

Legionnaires’ Disease, named after the outbreak in 1976 at the American Legion convention in Philadelphia, is caused by Legionella pneumonia and is characterized as an acute febrile respiratory illness ranging in severity from mild illness to fatal pneumonia. The disease occurs in both epidemic and endemic forms and sporadic cases are not easily differentiated from other respiratory infections by clinical symptoms. An estimated 25,000 to 100,000 cases of Legionella infection occur in the US annually. The resulting mortality rate, ranging from 25 to 40 percent, can be lowered if the disease is diagnosed rapidly and appropriate antimicrobial therapy in instituted early. Known risk factors include immunosuppression, cigarette smoking, alcohol consumption and concomitant pulmonary disease. The young and the elderly are particulary at risk.

Legionella pneumonia is responsible for 80-90% of reported cases of Legionella infection with serogroup 1 accounting for greater than 70% of all legionellosis. Current methods for the laboratory detection of pneumonia caused by Legionella pneumophilia 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 indirect fluroescent antibody (IFA). All of these rely on either obtaining an adequate respiratory specimen for sufficient sensitivity, or collecting sera at a two to six week interval. Unfortunately, one of the presenting signs of patients with Legionnaires’ Disease is the relative lack of productive sputum. In many patients, this necessitates the use of an invasive procedure to obtain a respiratory specimen. Diagnosis by serological techniques is usually retrospective in nature, and even then, patient compliance in obtaining the necessary specimen is poor.

The Binax Now^® Legionella Urinary Antigen Test allows for early diagnosis of Legionella pneumophilia serogroup 1 infection through detection of a specific soluble antigen present in the urine of patients with Legionnaires’ Disease. Legionella pneumophilia serogroup 1 antigen has been detected in urine as early as three days after the onset of symptoms. The test is rapid, giving the result in 15 minutes, and utilizes a urine specimen which is convenient for collection, transport, and subsequent detection of early, as well as later stages of disease.

Urine specimens should be collected in standard containers. The samples can be stored at room temperature if assayed within 24 hours of collection.

Positive Presumptive positive for L. pneumophilia serogroup 1 antigen in urine s suggesting current or past infection.

Negative Presumptive negative for L. pneumophilia serogroup 1 antigen in urine, suggesting no recent or current infection. Infection due to Legionella cannot be ruled out since other serogroups and species may cause disease, antigen may not be present in urine in early infection and the level of antigen present may be below the detection limit of the test.

The overall sensitivity and specificity of the test is 95%.

1. The test has only been validated using urine samples. Other samples such as serum, plasma, potable water, etc. cannot be used. The test has been validated on hospital patients only. Performance of the test has not been performed on diuretic urine.
2. This test will not detect infections caused by other serogroups and by other Legionella species. A negative test does not exclude infection with Legionella serogroup 1. Culture is recommended for suspected pneumonia to detect causative agents.
3. The diagnosis of Legionnaires’ Disease cannot be based on clinical or radiological evidence alone. Therefore, testing should be used in conjunction with clinical findings.
4. Excretion of Legionella antigen in the urine can vary depending on the patient. Antigen excretion may begin within 3 days after onset of symptoms and can persist for up to 1 year afterwards.