Different laboratory tests might be used in patients with aspiration pneumonia. Sputum analysis including lipid laden macrophage, gram stain and culture must be done in patients with cough. ABG may show acute hypoxemia and decreased mixed venous oxygen saturation. CBC shows leukocytosis with left shift or leukopenia, anemia, or thrombocytopenia.

Findings in routine blood tests are based on the severity of the disease and the cause, they can include the following:^[1]

• CBC shows:
  • Leukocytosis with left shift (in cases of bacterial pneumonia)
  • Leukopenia (in cases of atypical pneumonia)
  • Eosinophilia (in cases of eosinophilic pneumonia)
  • Anemia
  • Thrombocytopenia
• Hyponatremia
• Elevated BUN
• ABG may show:
  • Acute hypoxemia
  • Normal to low partial pressure of carbon dioxide
  • Decreased mixed venous oxygen saturation if a patient is in septic shock
  • Decreased HCO₃
  • High lactate level if a patient is in septic shock

• Sputum samples should be obtained in all patients with productive cough.^[2][3]
• A sputum sample is easy to obtain, however, many patients do not produce any sputum and repeated attempts may be required to obtain a representative sample.
• Sputum test however has questionable reliability and lipid-laden macrophages have been demonstrated in the absence of lipoid pneumonia.
• Gram stain and culture should be performed to assess the causative agent and guide the therapy.