Usefulness of PCR and antigen latex agglutination test with samples obtained by transthoracic needle aspiration for diagnosis of pneumococcal pneumonia.
In a large number of cases, the etiology of community-acquired pneumonia (CAP) is not established. Some cases are probably caused by Streptococcus pneumoniae. Transthoracic needle aspiration (TNA) culture has a limited sensitivity which might be improved by antigen detection or gene amplification techniques. We evaluated the capacity of a PCR assay and a latex agglutination test to detect S. pneumoniae in samples obtained by TNA from 95 patients with moderate-to-severe CAP. Latex agglutination and PCR had sensitivities of 52.2 and 91.3%, specificities of 88.7 and 83.3%, positive predictive values of 62.3 and 65.6%, and negative predictive values of 83.3 and 96.5%, respectively, when culture techniques were used as the "gold standard." When we considered expanded criteria for the diagnosis of pneumococcal pneumonia as a standard for our calculations, latex agglutination and PCR had sensitivities of 53.6 and 89.7%, specificities of 93.0 and 90.0%, positive predictive values of 78.9 and 81.3%, and negative predictive values of 80.3 and 94.7%, respectively. The additional diagnosis provided by the PCR assay compared to latex agglutination was 12.2% (95% confidence interval of the difference from 0.4 to 20. 1%). PCR was more sensitive than TNA culture, particularly in patients who had received prior antibiotic therapy (83.3 versus 33. 3%). Although PCR is a very sensitive and specific technique, it has not proved to be cost-effective in clinical practice. Conversely, latex agglutination is a fast and simple method whose results might have significant implications for initial antibiotic therapy.
García
A
A
Microbiology, Ciutat Sanitària i Universitària de Bellvitge, L'Hospitalet de Llobregat, Barcelona, Spain.
Rosón
B
B
Pérez
J L
JL
Verdaguer
R
R
Dorca
J
J
Carratalà
J
J
Casanova
A
A
Manresa
F
F
Gudiol
F
F
D000907:Antibodies, Bacterial / Q000097:blood; D001707:Biopsy, Needle; D003937:Diagnosis, Differential; D006785:Hospitals, University; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D007075:Immunoglobulin M / Q000097:blood; D007841:Latex Fixation Tests; D011015:Pneumonia, Aspiration / Q000175:diagnosis; D018410:Pneumonia, Bacterial / Q000175:diagnosis; D011018:Pneumonia, Pneumococcal / Q000175:diagnosis* / Q000276:immunology / Q000473:pathology; D016133:Polymerase Chain Reaction / Q000379:methods; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity; D013030:Spain; D013296:Streptococcus pneumoniae / Q000302:isolation & purification*; D013909:Thorax