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Detection of Streptococcus pneumoniae antigen in bronchoalveolar lavage fluid samples by a rapid
Jan A Jacobs1, Ellen E Stobberingh, Elisa I M Cornelissen
1Department of Medical Microbiology, University Hospital of Maastricht, P.O. Box 5800, 6202 AZ Maastricht, The Netherlands. jja@lmib.azm.nl
Abstract:
We conducted a retrospective study to evaluate an immunochromatographic membrane test (ICT), applied to bronchoalveolar lavage (BAL) fluid samples obtained in patients with suspected pneumonia, for the detection of Streptococcus pneumoniae antigen. The NOW Streptococcus pneumoniae test was assessed on 96 BAL fluid samples. Sensitivity was tested in 20 samples obtained from patients diagnosed as having pneumococcal pneumonia (growth of S. pneumoniae in blood cultures and/or in BAL fluid samples of > or =10(4) CFU/ml). Specificity was tested in BAL fluid samples of nonpneumococcal etiology (n = 41) and in samples with no respiratory pathogen and a total bacterial count of <10(4) CFU/ml (n = 35). Using the ICT, pneumococcal antigen was detected in 29 (30.2%) BAL fluid samples, with a sensitivity of 95.0% (95% confidence interval [CI], 90.6% to 99.4%) and a specificity of 86.8% (95% CI, 80.1% to 93.8%). The ICT was easy to perform and revealed unequivocal and reproducible results. No interference was observed with high cell counts, red blood cells, or elevated protein levels. Four out of 10 false-positive readings occurred in samples with S. pneumoniae counts below the 10(4) CFU/ml threshold limit of pneumonia. In BAL fluid samples obtained after pneumococcal bacteremia, positive test results were found for up to 35 days after bacteremia. The ICT test applied to BAL fluid specimens is reproducible and accurate in the diagnosis of pneumococcal antigen. Further studies are required to establish the impact of the ICT on patient care.
Insights
This study found the immunochromatographic membrane test (ICT) accurately detects Streptococcus pneumoniae antigen in bronchoalveolar lavage fluid. The test offers high sensitivity and specificity for diagnosing pneumococcal pneumonia.
Area of Science:
- Microbiology
- Infectious Diseases
- Diagnostic Testing
Background:
- Pneumonia diagnosis relies on identifying causative pathogens.
- Streptococcus pneumoniae is a common cause of bacterial pneumonia.
- Rapid diagnostic tools for pneumococcal pneumonia are needed.
Purpose of the Study:
- To evaluate the performance of an immunochromatographic membrane test (ICT) for detecting Streptococcus pneumoniae antigen.
- To assess the sensitivity and specificity of the NOW Streptococcus pneumoniae test using bronchoalveolar lavage (BAL) fluid.
Main Methods:
- A retrospective study analyzed 96 BAL fluid samples from patients with suspected pneumonia.
- Sensitivity was determined in 20 confirmed pneumococcal pneumonia cases.
- Specificity was assessed in 41 non-pneumococcal pneumonia cases and 35 controls.
Main Results:
- The ICT detected pneumococcal antigen in 30.2% of BAL samples.
- Sensitivity was 95.0% and specificity was 86.8%.
- The test demonstrated reproducibility and was unaffected by sample conditions; however, some false positives occurred below the pneumonia threshold.
Conclusions:
- The ICT is a reproducible and accurate method for detecting Streptococcus pneumoniae antigen in BAL fluid.
- Further research is needed to determine the clinical impact of this diagnostic test on patient management.
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