Archive for the “Lung Health” Category

Posted on 22 Sep 2014
Lung Health

Detection of Streptococcus pneumoniae

The results of the present study showed that PCR on pleural fluid samples can be a valuable test to diagnose pneumococcal pneumonia. The sensitivity and the specificity of the method were 78% and 93%, respectively, in patients with pneumonia, attending to results provided by alternative techniques. In comparison, the sensitivity of pleural fluid culture was only 22%. In addition, the PCR results were positive in 12% of patients with pneumonia of unknown etiology; although these cases were considered as false-positive results, they might certainly represent patients with pneumococcal pneumonia undetected by conventional methods. Unfortunately, a few unquestionably false-positive results were observed in the study of patients without pneumonia.

Prospective studies evaluating the etiology of CAP in adults have failed to identify the cause in 40 to 60% of patients. Blood cultures are very specific, but they have a low sensitivity, and the significance of Gram stain and culture of sputum is uncertain.2 In this context, pleural fluid, when present, can be considered as an attractive target to perform etio-logic studies for several reasons. First, a significant amount of parapneumonic effusion is detected by chest radiography in approximately 40% of patients with CAP.1 Second, in addition to the microbiology, biochemical examination is very useful for guiding therapeutic decisions; therefore, when a clinically important effusion is present, the pleural aspiration should be done routinely. And finally, the technique is not uncomfortable for patients, is associated with a low risk of complications, and always provides a valuable and specific sample, if we exclude a potential contamination by the habitual skin flora. However, the bacteriologic study of pleural fluid, based on Gram stain and cultures, is limited by the lack of sensitivity, particularly when criteria for empyema or complicated parapneumonic effusion are absent.14 Therefore, investigations with the use of new and more sensitive tests are needed.