14
Diagnosis
Table 5. Chest HRCT Scan Features of the Fibrotic HP
Pattern
HRCT
Pattern Typical HP
Compatible with
GHP
Indeterminate
for HP
Description e "typical HP"
pattern is suggestive
of a diagnosis of
HP. It requires a) an
HRCT pattern of
lung fibrosis (as listed
below) in one of the
distributions and b) at
least one abnormality
that is indicative of
small airway disease.
"Compatible-with-HP"
patterns exist when the
HRCT pattern and/
or distribution of lung
fibrosis varies from
that of the typical HP
pattern; the variant
fibrosis should be
accompanied by signs of
small airway disease.
e "indeterminate-
for-HP" pattern
exists when the
HRCT is neither
suggestive nor
compatible with a
typical and probable
HP pattern.
Relevant
radiological
findings
HRCT abnormalities
indicative of lung
fibrosis are most
commonly composed
of irregular linear
opacities/coarse
reticulation with lung
distortion. Traction
bronchiectasis and
honeycombing may
be present but do not
predominate.
Various patterns of lung
fibrosis:
• UIP pattern: basal
and subpleural
distribution of
honeycombing with/
without traction
bronchiectasis (per
2018 diagnosis of
IPF guidelines)
• Extensive GGOs
with superimposed
subtle features of
lung fibrosis
Lone patterns (i.e.,
not accompanied
by other findings
suggestive of HP) of:
• UIP pattern
(as per 2018
IPF diagnosis
guidelines)
• Probable
UIP pattern
(as per 2018
IPF diagnosis
guidelines)
• Indeterminate
pattern for UIP
(as per 2018
IPF diagnosis
guidelines)
• Fibrotic NSIP
pattern
• Organizing
pneumonia–like
pattern
e distribution of
fibrosis may be:
• Random both
axially and
craniocaudally or
• Mid lung zone–
predominant or
• Relatively spared
in the lower lung
zones
Variant (predominant)
distributions of lung
fibrosis:
• Axial:
peribronchovascular,
subpleural areas
Distribution of
parenchymal
abnormalities:
• Craniocaudal:
diffuse (with or
without some basal
sparing )
• Axial: diffuse
