TABLE 1

Histological scoring criteria

InflammationCriteria for score of:
0123
Interstitial<2 inflammatory cells/alveolar septal diam2–5 inflammatory cells/alveolar septal diam6–25 inflammatory cells/alveolar septal diam involving <5% of the parenchyma6–25 inflammatory cells/alveolar septal diam involving >5% of the parenchyma
PeribronchiolarRare inflammatory cellsMild; 250–1,000 inflammatory cells/mm2 involving <10% of bronchiolar circumferenceModerate; >1,000 inflammatory cells/mm2 involving <25% of bronchiolar circumferenceSevere; >1,000 inflammatory cells/mm2 involving >25% of bronchiolar circumference
PerivascularRare inflammatory cellsMild; 250–1,000 inflammatory cells/mm2 involving <10% of arteriolar circumferenceModerate; >1,000 inflammatory cells/mm2 involving <25% of arteriolar circumferenceSevere; >1,000 inflammatory cells/mm2 involving >25% of arteriolar circumference