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Evaluation of a rapid urine pneumococcal antigen test performed among pediatric patients Evaluation of a rapid urine pneumococcal antigen test performed.

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Presentation on theme: "Evaluation of a rapid urine pneumococcal antigen test performed among pediatric patients Evaluation of a rapid urine pneumococcal antigen test performed."— Presentation transcript:

1 Evaluation of a rapid urine pneumococcal antigen test performed among pediatric patients Evaluation of a rapid urine pneumococcal antigen test performed among pediatric patients F. Pagès-Jandot, A.M. Freydière, F. Vandenesch, C. Ploton. Laboratoire de Bactériologie, Hôpital Debrousse, Hospices Civils de Lyon, France Introduction and objectives Streptococcus pneumoniae prevails as the most common pathogen of community acquired pneumonia (CAP). Systemic pneumococcal infection is a major cause of morbidity and mortality, especially for young children. Microbiological diagnosis of pneumococcal CAP, based on blood or sputum cultures, is poorly efficient (1), particularly in children. The purpose of this study was to evaluate Binax Now  Streptococcus pneumoniae urinary antigen test, a rapid immunochromatographic test, in pediatric patients by testing urines sample from 80 children hospitalised with CAP and from 20 children without CAP. Material and methods Pneumonia group: 80 urines samples from children (age range: 1 month-15 years; median 4 years) with CAP defined by the presence of infectious syndrome (fever, leucocytosis, elevation of C-reactive protein), cough, sputum production and pulmonary infiltrates on the chest radiograph. Microbiological analysis included blood culture for 100% of children and sputum or broncho-alveolar-lavage (BLA) culture for 40% of them. Control group : 20 urines samples from children (age range: 2 months-15 years; median 4 years) admitted to hospital for non-CAP infections (including meningitis, urinary tract infections, asthma…). Results and discussion Pneumonia group The Binax Now® Streptococcus pneumoniae antigen urinary test was far more sensitive than conventional microbiological methods. Moreover this test is rapid (15 minutes), easy to use and non invasive. Thus, in spite of some false positive results in the control group due to nasopharyngeal pneumococci carriers, this test is a useful adjunct to clinical evidences and to bacteriological culture for an early diagnosis of pneumococcal CAP in pediatric patients. However, its use should be restricted to selected patients population (CAP) in order to maximize the specificity. References VPN = 75% VPP = 95% Control group 20 children without pneumonia 7 Binax Now® positive 3 S. pneumoniae meningitidis (Binax Now® yielded also a positive result with CSF) 4 nasopharyngeal carriers of pneumococci 13 Binax Now® negative Among the 48 patients with clinical, biological and radiological evidences for S. pneumoniae CAP, 10 were positive with conventional microbiological methods, while 38 were positive with the Binax Now®. The low sensitivity of microbiological methods could be due either to spontaneous lysis of the bacteria in blood specimens or to an initial antibiotic treatment. Among the 32 patients with evidence for other etiology of CAP; 2 patients with Haemophilus influenzae pneumonia yielded a Binax Now® positive result. There could be a cross-reactivity between S. pneumoniae C-polysaccharide and Haemophilus influenzae, or a mixed infection with 2 micro-organisms (4). In the present study, the Binax Now® showed a high specificity probably because of the very selective inclusion criteria for the pneumonia group. The Binax Now® results among nasopharyngeal carriers of pneumococci should be evaluated with a larger control group. As a matter of fact, the rate of nasopharyngeal colonisation range from 30 to 60 % among 2-5 years old children (2, 3), and it would be important to precise the rate of positive Binax Now ® among these carriers. However, in the absence of a reliable “gold standard method” this goal is difficult to achieve. The PCR method might be an alternative reference method in the future (5). Acknowledgements We thank the technicians of our laboratory and A. Frangin for her help in producing this poster. Table: Binax NOW® S. pneumoniae results in urine specimens of 80 children with CAP. Xth IUMS Paris 2002 In absence of pneumococcal antigens, the antibodies conjugated in excess are captured by immobilised goat anti-rabbit IgG, forming the control line. The resulting antigens-antibodies conjugated complexes are captured by immobilised anti-S. pneumoniae antibodies, forming the sample line. or 1- Murdoch D.R., R.T. Laing, G.D. Mills, N.C. Karalus, G.I. Town, S. Mirett and L.B. Reller Evaluation of a rapid immunochromatographic test for detection of Streptococcus pneumoniae antigen in urine samples from adults with Community acquired-Pneumonia.J. Clin. Microbiol 39: Dominguez J., N. Gali, S. Blanco, P. Pedroso, C. Prat, L. Matas and V. Ausina Detection of Sreptococcus pneumoniae antigen by a rapid immunochromatographic assay in urines samples. Chest 119: Dowell S.F., R.L. Garman, G. Liu, O.S. Levine and Y.H. Yang Evaluation of Binax NOW, an assay for the detection of pneumococcal antigen in urine samples, performed among pediatric patients. Clin. Infect. Dis. 32: Burel E., P. Dufour, V. Gauduchon, S. Jarraud and J. Etienne Evaluation of a rapid immunochromatographic assay for detection of Streptococcus pneumoniae antigen in urine samples. Eur. J. Clin. Microbiol. Infect. Dis. 20: Michelow I.C., J. Lozano, K. Olsen, C. Goto, N. K. Rollins, F. Ghaffar, V. Rodriguez-Cerrato, M. Leinonen and G.H. Mc Cracken Diagnosis of Streptococcus pneumoniae lower respiratory infection in hospitalized children by culture, Polmerase Chain Reaction, serological testing and urinary antigen detection. Clin. Infect. Dis 34: Clinical, biological and radiological evidences for S. pneumoniae CAP (n = 48) Clinical, biological and radiological evidences for other etiology of CAP (n = 32) Positive culture a with S. pneumoniae Negative culture Binax NOW® positive (40) Binax NOW® negative (40) Positive culture with organisms other than S. pneumoniae Negative culture 10 a b2b 11 c 0 19 Sensitivity = 79 % Specificity = 94 % a - Sputum or blood culture b - Haemophilus influenzae b (HI b) c - HI b, M. pneumoniae, VRS, Branhamella catarrhalis Methodology A swab is dipped into the urine sample. Migration buffer is added and the device is closed. - +  15 min Interpretation The swab is inserted into the test device. S. pneumoniae antigens present in the urine sample react to bind anti-S. pneumoniae conjugated antibodies Conclusion


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