Comparisons of clinical characters in patients with pneumococcal and Legionella pneumonia

Background/purpose: The etiology of pneumonia is usually unknown, but the availability of urinary pneumococcal and Legionella antigen tests can improve the diagnostic yield. Our aim was to provide clinical clues to help clinicians perform the appropriate urinary antigen tests.

Methods: A retrospective study of patients admitted to the National Cheng Kung University Hospital between July 2006 and June 2008 was conducted. Patients aged over 18 years presenting with clinical symptoms and signs, radiological findings compatible with pneumonia, and a positive pneumococcal or Legionella pneumophila urinary antigen test, were included. Medical records were reviewed for data collection.

Results: Overall, 55 adults with pneumonia, including 42 with pneumococcal pneumonia (PP) and 13 with Legionella pneumonia (LP), were enrolled. On admission, patients with PP tended to be older (73.5 years vs. 59.1 years; p=0.001), had lower body weights (52.0 kg vs. 69.7 kg; p < 0.001), more frequent respiratory symptoms (59.5%vs. 0%; p < 0.001), and lower systolic (123.0 mmHg vs. 141.0 mmHg; p=0.004) and diastolic blood pressures (68.3 mmHg vs. 81.7 mmHg; p=0.008), compared with patients with LP. However, those with LP had higher body temperatures (39.0°C vs. 37.5°C; p < 0.001), a higher incidence of relative bradycardia (45.5%vs. 0%; p < 0.001), diarrhea (15.4%vs. 0%; p= 0.053), and lower platelet counts (178.5 × 10(3)/mm(3)vs. 233.7 × 10(3)/mm(3); p= 0.026). Radiological findings showed that the major abnormality, lobar consolidation, was indistinguishable between LP and PP. The percentage of patients requiring intensive care (35.7%vs. 38.5%) or ventilator support (31%vs. 23.1%) and in-hospital crude mortality rates (9.5%vs. 7.7%) was similar in both groups.

Conclusion: Some clinical and laboratory characteristics may be regarded as important clues indicating the need for an appropriate urinary antigen test in patients with pneumonia.