Prognostic assessment of pleural effusion: the American College of Chest Physicians guidelines

Pleural space anatomyPleural fluid bacteriologyPleural fluid chemistryCategoryRisk of poor outcomeDrainage
Minimal, free-flowing effusion (< 10 mm on lateral decubitus image)andCulture and Gram stain results unknownandpH unknown1Very lowNo
Small to moderate free- flowing effusion (> 10 mm and < 1/2 hemithorax)andNegative culture and Gram stainandpH ≥ 7.202LowNo
Large, free-flowing effusion (≥ 1/2 hemothorax), loculated effusion, or effusion with thickened parietal pleuraorPositive culture and Gram stainorpH < 7.203ModerateYes