Blood Tests for Lung Abscess: Supportive but Not Diagnostic Alone

Blood tests complement imaging (CXR, CT) and microbiology in lung abscess diagnosis but cannot confirm it independently.

Key Blood Markers

• CRP/ESR: Elevated in inflammation/infection; nonspecific.
• CBC with differential: Leukocytosis with left shift (neutrophilia) supports bacterial infection.
• Procalcitonin: More specific for bacterial sepsis; guides antibiotic duration.
• Blood cultures: Positive in 20–30% of lung abscesses; identifies organism and sensitivities.
• Electrolytes, renal/liver function: Assess systemic impact, guide dosing.
• ABG: Evaluates gas exchange if extensive disease.

Definitive Diagnosis Requires

• Imaging: Cavitary lesion with air-fluid level on CXR/CT
• Sputum/ETT culture: Identifies pathogen
• Bronchoscopy: Excludes obstruction, obtains lower airway samples

Blood tests inform severity, organism, and organ function; imaging + microbiology confirm.