Legionella Urinary Antigen Test Research Articles

Sensitivity of urinary antigen test in relation to clinical severity in a large outbreak of Legionella pneumonia in Spain

Presented here are the results of Legionella urinary antigen testing correlated with patient characteristics and severity of pneumonia (Fine score) in 295 patients diagnosed with Legionella pneumonia in connection with a large outbreak in Murcia, Spain. Overall, the sensitivity of the urinary antigen test was 47.7% (141/295). A statistically significant association was found between the clinical severity of pneumonia and test sensitivity; 85.7% for patients with severe pneumonia versus 37.9% for patients with mild pneumonia (risk ratio, 2.3). Variables significantly associated with test positivity in multivariate analysis were as follows: pre-existing pulmonary disease, body temperature >40 degrees C, leukocytosis and multilobar infiltrates. Patients with mild pneumonia may go undiagnosed if the urinary antigen test is used alone.

Legionnaires' Disease in Long‐Term Care Facilities: Overview and Proposed Solutions

Pneumonia is a leading cause of morbidity and mortality in nursing home patients. In acute care hospitals, there is considerable evidence to indicate that Legionnaires' disease is a significant cause of nosocomial pneumonia, the source of which is the potable water system. A relatively limited amount of data exists as to the role of Legionnaires' disease as a cause of pneumonia acquired in long-term care residents. Several lines of evidence suggest that Legionnaires' disease may be an important but underrecognized cause of pneumonia in long-term care residents. These include reports of outbreaks, prospective studies of community-acquired pneumonia that include nursing home patients, and prospective studies of individual long-term care facilities linking Legionnaires' disease to colonization of the potable water system with Legionella. Multiinstitutional studies combining environmental and clinical surveillance for Legionella are needed to further confirm the relationship between colonization of potable water and the occurrence of disease in the long-term care facilities. Until these studies are completed, it is recommended that individual facilities undertake annual sampling of the potable water system for Legionella, coupled with introduction of the rapid Legionella urinary antigen test should L. pneumophila serogroup 1 be found.

Impact of positive legionella urinary antigen test on patient management and improvement of antibiotic use

Aim: To assess the incidence of legionella infection over a 27 month period at a large university hospital. Material and Methods: The present retrospective cohort study enrolled patients with legionellosis,...

Legionnaires' disease: update on epidemiology and management options.

Infection with Legionella spp. is an important cause of serious community- and hospital-acquired pneumonia, occurring sporadically and in outbreaks. Outbreaks of Legionnaires' disease have recently received considerable media attention, and some factors indicate that the problem will increase in future. Infection with Legionella spp. ranks among the three most common causes of severe pneumonia in the community setting, and is isolated in 1-40% of cases of hospital-acquired pneumonia. Underdiagnosis and underreporting are high. Only 2-10% of estimated cases are reported. Detection of a single case should not be considered an isolated sporadic event, but rather indicative of unrecognized cases. There are no clinical features unique to Legionnaires' disease; however, suspicion should be raised by epidemiologic information commensurate with the diagnosis and the presence of headache, confusion, hyponatremia, elevated creatine kinase and/or severe pneumonia. An arterial oxygen partial pressure <60mm Hg on presentation and progression of pulmonary infiltrates despite appropriate antibacterial therapy should always alert clinicians to this cause.Macrolides, fluoroquinolones and rifampin (rifampicin) are the most widely used drugs in treatment. Fluoroquinolones or azithromycin are the treatment of choice in immunosuppressed patients and those with severe pneumonia. Incorporation of the legionella urinary antigen test in emergency departments in hospitals and progressive improvement in this test will, in the near future, permit appropriate diagnosis and treatment of this frequent, sometimes severe, illness.

Severe Acute Respiratory Syndrome: The Evolution of a New Epidemic

Severe Acute Respiratory Syndrome: The Evolution of a New Epidemic

Neumonía comunitaria por Legionella pneumophila serogrupo 1. Estudio de 97 casos

Legionella pneumophila is the causal agent of 5% to 12% of sporadic community-acquired pneumonia cases, though rates are changing with the use of new diagnostic methods. This is a retrospective study of all patients admitted to our hospital with community-acquired pneumonia due to Legionella pneumophila between 1997 and 2001. Diagnostic criteria included either a positive Legionella serogroup 1 urinary antigen test or seroconversion and a chest radiograph consistent with pneumonia. A total of 97 patients were studied. Ninety cases (92.8%) were community-acquired and 7 (7.2%) were associated with travelling. In 82 cases (84.5%) the presentation was sporadic. Seventy-five patients were smokers (77.3%). The most common symptoms were fever in 91 patients (93.8%) and cough in 67 (68.1%). In five patients (5.2%) creatine phosphokinase concentrations were over 5 times their baseline values (in two over 100 times); four of these patients presented acute renal failure. Seroconversion was observed in 23/42 patients (54.8%). There were no statistically significant differences between the administration of erythromycin or clarithromycin in monotherapy, or in combination with rifampin. Nineteen patients (19.6%) presented acute renal failure and mechanical ventilation was necessary in 22 (22.7%). Twelve patients died (12.5%). Independent prognostic factors associated with death included respiratory rate > 30 breaths/min, urea > 60 mg/dL and PaO2 < 60 mmHg. A significant linear association was found between severity scale scores and the presence of complications or mortality. The Legionella urinary antigen test permits early diagnosis and treatment of this disease. The severity scale is an indicator of complications or death.

The impact of diagnosis by legionella urinary antigen test on the epidemiology and outcomes of Legionnaires' disease.

Legionnaires' disease is an uncommon but important cause of life-threatening community-acquired or nosocomial pneumonia. The urinary antigen enzyme immunoassay test, used in Victoria since 1995, now accounts for the majority of initial laboratory notifications (81% in 1999). We review the impact of the test on the disease epidemiology and the public health investigative process. We focus on the major subgroup of cases due to Legionella pneumophila serogroup 1, comparing delays until notification and mortality for urinary antigen detected cases with culture detected cases. The urinary antigen test facilitates a 5-day reduction for the delay between onset of illness and notification. We observed that there was minimal clinical heterogeneity of urinary antigen detected cases whether they were subsequently culture confirmed or not. We encourage clinician use of the urinary antigen test in cases of community-acquired pneumonia where Legionnaires' disease is a possible diagnosis, in conjunction with culture of clinical specimens.

Evaluation of the Winthrop-University Hospital Criteria to Identify Legionella Pneumonia

To measure the ability of a set of clinical parameters, the Winthrop-University Hospital (WUH) criteria, to identify Legionella pneumonia while discriminating against bacteremic pneumococcal pneumonia at the time of hospitalization for community-acquired pneumonia (CAP). Retrospective case-control study. An urban county hospital and a tertiary-care Veterans Affairs hospital. Thirty-seven patients with Legionella pneumonia (diagnosed by a positive result of a urinary Legionella antigen test) and 31 patients with bacteremic pneumococcal pneumonia. A subgroup of patients with all required laboratory criteria were studied further. The WUH criteria correctly identified 29 of 37 patients with Legionella pneumonia (sensitivity, 78%; 95% confidence interval [CI], 61 to 90%), while successfully excluding legionellosis in 20 of 31 patients with bacteremic pneumococcal pneumonia (specificity, 65%; 95% CI, 45 to 80%). The positive and negative predictive values, adjusted for a relative prevalence of 1:3 between Legionella and Streptococcus pneumoniae bacteremia, were 42% (95% CI, 25 to 61%) and 90% (95% CI, 74 to 97%), respectively. In the subgroup analysis, the WUH criteria were successful in identifying 20 of 23 patients with Legionella pneumonia (sensitivity, 87%; 95% CI, 65 to 97%), while excluding legionellosis in 9 of 18 patients with bacteremic pneumococcal pneumonia (specificity, 50%; 95% CI, 27 to 73%). The adjusted positive and negative predictive values for a 1:3 relative prevalence were 37% (95% CI, 20 to 59%) and 92% (95% CI, 62 to 98%), respectively. The predictive values were changed in the directions expected for an increased relative prevalence of 1:1. The areas under the receiver operating characteristic curves were 0.72 +/- 0.06 for the entire study group and 0.68 +/- 0.09 for the subgroup. Although the WUH criteria discriminated fairly well between cases (mean +/- SE) and control subjects, the sensitivity is not high enough to exclude legionellosis confidently. These results suggest that empiric therapy for Legionella pneumonia should be included in the initial antibiotic regimen for hospitalized patients with CAP.

Laboratory diagnosis of Legionnaires' disease: The expanding role of the Legionella urinary antigen test

Introduction Legionnaires’ disease is pneumonia, caused by Legionella species. At least 39 Legionella species have been identified, but L. pneumophila causes approximately 90% of the reported cases of Legionnaires’ disease in the U.S. (1). Legionnaires’ disease has been aptly described as under-diagnosed but overtreated (2). The Centers for Disease Control and Prevention in Atlanta, GA (CDC) estimates that 18,000 to 25,000 cases of Legionnaires’ disease occur annually in the U.S. However, these figures underestimate the true incidence of Legionnaires’ disease (I ). Cases of Legionnaires’ disease go unrecognized because it is not possible to clinically distinguish Legionnaires’ disease from other causes of pneumonia, and the diagnostic tests for Legionella are not ordered routinely. The tests currently available for making the diagnosis of Legionnaires’ disease include culture isolation, visualization of the bacterium by direct fluorescent antibody (DFA) staining of respiratory secretions, serum antibody testing, and Legionella urinary antigen testing. The reported sensitivities of these tests vary widely depending on the study. The sensitivity of culture, DFA, serology, and the urinary antigen test has been reported to be between 40 to 80,25 to 75,40 to 75, and 70 to 90%. respectively (3-5). These tests should be performed by experienced microbiologists to achieve optimal results. Since many laboratories have inadequate experience with these tests, specimens for Legionella testing are often sent to a reference laboratory. Those laboratories that do perform Legionella diagnostic testing in-house may not do it well. A College of American Pathologists survey of laboratories showed that only 32% of laboratories successfully identified a pure culture of L. pneumophila (3). At the V.A. Medical Center Special Pathogens Laboratory, Pittsburgh, PA, we have found culture to be the most sensitive diagnostic method. We optimize the recovery of Legionella from culture by using multiple selective media and acid-buffer pretreatment of sputum specimens, but for many smaller laboratories this approach may be impractical (6). For pneumonia caused by L. pneumophifa serogroup 1, the urinary antigen test is a practical alternative to culture for the diagnosis of Legionnaires’ disease. The urinary antigen test has several advantages over culture. For many patients with Legionnaires’ disease, obtaining an adequate sputum specimen is difficult; urine, on the other hand, is easily obtained. The results of urinary antigen testing can be available within hours, whereas culture results require three to five days. The disadvantage of the urinary antigen test is that it is specific for L. pneumophila, serogroup 1 only. Since the vast majority of cases of Legionnaires’ disease are caused by this species and serogroup, this limitation has not been considered a major disadvantage of the test.

Evaluation of a rapid immunochromatographic assay for the detection of Legionella antigen in urine samples.

A new immunochromatographic membrane assay for detecting Legionella pneumophila serogroup 1 antigen in urine samples (Binax Now Legionella Urinary Antigen Test; Binax, USA) was evaluated. Its sensitivity, specificity and level of agreement with the Binax enzyme immunoassay were compared using nonconcentrated and concentrated urine samples. The overall agreement between the two tests was 98.1%; the specificity of both was 100%. The sensitivity of the immunochromatographic assay was 55.5% in nonconcentrated urine and 97.2% in concentrated urine in comparison with the enzyme immunoassay, using concentrated urine as the reference test. This immunochromatographic assay screens successfully for Legionella pneumophila serogroup 1 soluble antigen in concentrated urine samples.

Legionella urinary antigen testing: Potential impact on diagnosis and antibiotic therapy

Although Legionella is an important cause of severe pneumonia, difficulty still exists in its diagnosis. Because at least 80% of patients with legionellosis excrete the Legionella antigen in their urine, various methods have been investigated for urinary antigen detection. Specificity for these methods has been reported to be 100%, and sensitivity has been shown to vary between 70 and 100%. The advantages of these methods include ease of specimen collection, the ability to obtain large quantities of specimen for concentration, the ability to detect antigen after initiation of antibiotic therapy, and the ability to obtain results quickly. Disadvantages include the ability to only reliably detect urinary L. penumophila serogroup 1 antigen and the inability to diagnose relapse or reinfection due to persistence of antigen excretion. Of the commercially-available detection methods, the polyclonal enzyme-linked immunosorbent assay (ELISA) appears to be most efficient. Its use with routine Legionella screening procedures should be considered in target populations, with the intent of early diagnosis and antibiotic therapy streamlining.

Legionella Urinary Antigen in Early Disease

The results of Legionella urinary antigen testing were correlated to the interval between onset of disease and sampling of urine in 134 patients in connection with a large outbreak of Legionnaires' disease at a Swedish hospital. In 17 patients with the disease, 5/7 sampled during the first 5 days of illness proved negative in the urinary antigen test. The risk of obtaining negative results during the first days of the disease is emphasized.