Bacterial pneumonia laboratory findings
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Arooj Naz
Overview
Patients infected with bacterial pneumonia present with a high leukocyte count as well as elevated inflammatory biomarkers. Other tests routinely done include electrolyte assessment, renal function tests, arterial blood gasses. pulse oximetry, gram staining and sputum samples. Blood cultures and PCR tests are sensitive tests that can provide a definitive diagnosis and aid in the selection of antibiotics.
Laboratory Findings
CBC
- RBC: Anemia
- WBC: Significant leukocytosis (with left shift), leukopenia may present in cases of atypical pneumonia
- Platelets: Thrombocytopenia
Electrolytes
- Electrolytes are particularly helpful but hyponatremia may be present in cases of Legionella
Inflammatory biomarkers
- Erythrocyte sedimentation rate: Elevated
- C-reactive protein: Elevated (> 100 mg/L)
RFTs
- BUN: elevated
Arterial Blood Gas
- Hypoxia
- Respiratory acidosis (pH <7.2, bicarbonate <22 mEq/L)
Pulse oximetry
- < 92% indicates severe hypoxia
Blood Culture
- Blood culture samples are necessary in diagnosing the bacterial agent responsible. Samples should be taken before administering antibiotics
- A common practice in hospitalized patients
Gram staining
- Gram staining can identify if an organism is gram positive, gram negative, or does not have a cell wall as in the case of Mycoplasma
Sputum samples
- Sputum samples should be obtained when patient presents with a productive cough
- A common practice in hospitalized patients
Polymerase Chain Reaction
- PCR results are very rapid and sensitive for detection of bacteria[2]