Table 1.

—Categorizing Risk for Poor Outcome in Patients With PPE

Pleural Space Anatomy		Pleural Fluid Bacteriology		Pleural Fluid Chemistrya	Category	Risk of Poor Outcome	Drainage
A0 minimal, free-flowing effusion (< 10 mm on lateral decubitus)b	AND	Bx culture and Gram stain results unknown	AND	Cx pH unknown	1	Very low	Noc
A1 small to moderate, free-flowing effusion (> 10 mm and < 1/2 hemithorax)	AND	B0-negative culture and Gram staind	AND	C0 pH ≥ 7.20	2	Low	Noe
A2 large, free-flowing effusion (≥ 1/2 hemithorax),f loculated effusion,g or effusion with thickened parietal pleurah	OR	B1-positive culture or Gram stain	OR	C1 pH < 7.20	3	Moderate	Yes
		B2 pus			4	High	Yes

PPE = parapneumonic effusion. Reprinted with permission from Colice et al.²

^apH is the preferred pleural fluid chemistry test, and pH must be determined with a blood gas analyzer. If a blood gas analyzer is not available, pleural fluid glucose should be used (P₀ glucose ≥ 60 mg/dL; P₁ glucose < 60 mg/dL). The American College of Chest Physicians Parapneumonic Effusions Panel cautions that the clinical utility and decision thresholds for pH and glucose have not been well established.

^bClinical experience indicates that effusions of this size do not require thoracentesis for evaluation but will resolve.

^cIf thoracentesis were performed in a patient with A₀ category pleural anatomy and P₁ or B₁ status found, clinical experience suggests that the P₁ or B₁ findings might be false positive. Repeat thoracentesis should be considered if effusion enlarges or clinical condition deteriorates.

^dRegardless of prior use of antibiotics.

^eIf clinical condition deteriorates, repeat thoracentesis and drainage should be considered.

^fLarger effusions are more resistant to effective drainage possibly because of the increased likelihood that large effusions will also be loculated.

^gPleural loculations suggest a worse prognosis.

^hThickened parietal pleura on contrast-enhanced CT scan suggests presence of empyema.