Table 1.

HRCT Criteria for the UIP Pattern.

UIP	Probable UIP	Indeterminate for UIP	Alternative diagnosis
- Predominantly subpleural and basal distribution - Reticular abnormality - Honeycombing with or without traction bronchiectasis	- Predominantly subpleural and basal distribution - Reticular abnormality with peripheral traction bronchiectasis - May have mild GGO	- Predominantly subpleural and basal distribution - Mild reticulation, mild GGO or distortion - CT features that do not suggest any specific etiology	- Distribution other than subpleural/basal - Extensive GGO (extension > reticular abnormality) - Profuse micronodules (bilateral, predominantly upper lobes) - Discrete cysts (multiple, bilateral, apart from areas of honeycombing) - Diffuse mosaic attenuation/air-trapping (bilateral, in three or more lobes) - Consolidation in bronchopulmonary segment(s)/lobe(s)

CT: Computed Tomography; GGO: Ground-glass Opacity; UIP: Usual Interstitial Pneumonia; >: Greater Than.

Adapted from Raghu et al. (6).