TABLE 1.

Histological scoring criteria

Inflammation	Criteria for score of:
	0	1	2	3
Interstitial	<2 inflammatory cells/alveolar septal diam	2–5 inflammatory cells/alveolar septal diam	6–25 inflammatory cells/alveolar septal diam involving <5% of the parenchyma	6–25 inflammatory cells/alveolar septal diam involving >5% of the parenchyma
Peribronchiolar	Rare inflammatory cells	Mild; 250–1,000 inflammatory cells/mm2 involving <10% of bronchiolar circumference	Moderate; >1,000 inflammatory cells/mm2 involving <25% of bronchiolar circumference	Severe; >1,000 inflammatory cells/mm2 involving >25% of bronchiolar circumference
Perivascular	Rare inflammatory cells	Mild; 250–1,000 inflammatory cells/mm2 involving <10% of arteriolar circumference	Moderate; >1,000 inflammatory cells/mm2 involving <25% of arteriolar circumference	Severe; >1,000 inflammatory cells/mm2 involving >25% of arteriolar circumference