Diagnostic Approaches for Suspected Pneumonia

Recommendations for Blood Cultures

The American Thoracic Society recommends blood cultures for patients with severe community-acquired pneumonia (CAP) 1, 2, 3
Blood cultures should be obtained for patients being empirically treated for MRSA or Pseudomonas aeruginosa, as recommended by the American Thoracic Society 1, 2
The American Thoracic Society suggests blood cultures for patients previously infected with MRSA or P. aeruginosa, especially with prior respiratory tract infection 1
Patients hospitalized and received parenteral antibiotics in the last 90 days should have blood cultures obtained, according to the American Thoracic Society 1

The yield of blood cultures is low in non-severe CAP, with a positivity rate of 2% in outpatients and 9% in inpatients, as reported by the American Thoracic Society 2, 4
Blood cultures may generate false-positive results, leading to unnecessary antibiotic use, as noted by the American Thoracic Society 2, 4
The collection of blood cultures is associated with increased length of stay and duration of antibiotic therapy, according to the American Thoracic Society 2, 4

The American Thoracic Society recommends sputum cultures for patients with severe CAP 1, 3, 5
Sputum cultures should be obtained for patients being empirically treated for MRSA or P. aeruginosa, as recommended by the American Thoracic Society 1
The American Thoracic Society suggests sputum cultures for patients who do not respond to empirical antibiotic therapy 3, 5
Sputum cultures should be collected before antibiotic administration whenever possible, as recommended by the American Thoracic Society 6, 7

Good-quality specimens (fewer than 10 squamous epithelial cells and >25 neutrophils per low-power field) are essential for sputum cultures, according to the American Thoracic Society 7
Sputum samples should be transported rapidly to the laboratory, as recommended by the American Thoracic Society 3

For outpatients with suspected CAP, microbiological investigations including sputum cultures are not recommended routinely, as stated by the American Thoracic Society 3, 5
For hospitalized patients with non-severe CAP who can expectorate purulent samples and have not received prior antibiotics, sputum samples should be sent for culture, according to the American Thoracic Society 3, 5
If a sputum culture is obtained, it should be correlated with Gram stain findings, as recommended by the American Thoracic Society 6

Delaying antibiotic administration to collect cultures can worsen outcomes, as noted by the American Thoracic Society 7
Interpreting culture results without considering quality of the specimen can lead to inappropriate treatment, according to the American Thoracic Society 7
Changing antibiotics based on contaminants in blood cultures can lead to inappropriate antimicrobial use, as reported by the American Thoracic Society 2, 4