Table 2 Distinguishing clinical features of idiopathic pulmonary fibrosis (IPF) and non-specific interstitial pneumonia (NSIP)

Clinical/radiographic/pathological features	IPF	NSIP
Duration of illness	Chronic (>12 months)	Subacute to chronic (months to years)
Frequency of diagnosis	47–64%	14–36%
Chest radiograph	Bilateral reticular opacities in lower zones; volume loss; ± honeycombing	Bilateral hazy and reticular opacity
HRCT	Peripheral, subpleural, basal predominance	Peripheral, subpleural, basal, symmetrical
	Reticular opacities	Ground-glass attenuation
	Honeycombing	Consolidation
	Traction bronchiectasis	Lower lobe volume loss
	Architectural distortion.
	Focal ground-glass
Key histological features	Usual interstitial pneumonia patternDense fibrosis causing remodeling of lung architecture with frequent “honeycomb” fibrosisFibroblastic foci typically scattered at the edges of dense scarsPatchy lung involvementFrequent subpleural and paraseptal distribution	NSIP patternCellular patternMild to moderate interstitial chronic inflammationType II pneumocyte hyperplasia in areas of inflammationFibrosing patternDense or loose interstitial fibrosis lacking the temporal heterogeneity pattern and/or patchy features of UIPLung architecture may appear lost on examination of H&E stained sections but relatively preserved with elastic stainsInterstitial chronic inflammation (mild or moderate)







Treatment	Poor response to any treatment	Corticosteroid responsiveness
Prognosis	50–70% mortality in 5 years	Unclear; <15% mortality in 5 years