Mll. Lorente et al., Diagnosis of pneumococcal pneumonia by polymerase chain reaction (PCR) in whole blood: a prospective clinical study, THORAX, 55(2), 2000, pp. 133-137
Background-Streptococcus pneumoniae is the leading cause of community acqui
red pneumonia; however, only a small proportion of cases can be detected by
conventional methods. The ability of the polymerase chain reaction (PCR) t
est performed on whole blood samples to identify patients with pneumococcal
pneumonia was investigated.
Methods-One hundred and fourteen consecutive adult patients with community
acquired pneumonia were evaluated by a wide battery of diagnostic tests in
order to determine the aetiology. Blood samples from these patients and 50
controls were also tested by the nested PCR test to detect selected pneumol
ysin gene fragments of S pneumoniae.
Results-The patients were divided into four groups: (1) 40 patients with pn
eumococcal pneumonia in 22 of whom (55%) the PCR was positive (eight of 11
with bacteraemia and 14 of 29 without); (2) 30 with pneumonia due to other
pathogens in all of whom the PCR was negative; (3) 44 with pneumonia of unk
nown aetiology in 14 of whom (32%) PCR was positive, and (4) 50 controls in
whom the PCR test was positive in two (4%). Thus, the sensitivity of the t
est was 55% and the specificity 100% (81% if positive PCR tests among undia
gnosed patients are considered as false positive results).
Conclusion-PCR applied to whole blood samples appears to be a sensitive and
very specific diagnostic test for identifying patients with pneumococcal p
neumonia with a potential application in clinical practice.