Table 2.

Distribution of patients with fibrosing ILD (specific, two-claim definition) who progressed during follow-up, according to underlying disease

	Incident and existing fibrosing ILD			Incident fibrosing ILD only
	Patients, n	Patients with progression at any time, n*	Percent with progression at any time	Patients, n	Patients with incident progression, n*	Percent with incident progression	Median time to progression, days [IQR]†
All fibrosing ILD	35,825	21,719	60.6	23,577	13,518	57.3	117 [63, 224]
Unclassifiable IIP	24,881	15,515	62.4	17,385	10,241	58.9	115 [62, 219]
iNSIPs	196	150	76.5	106	69	65.1	67 [50, 176]
Sarcoidosis	2522	1160	46.0	1740	744	42.8	148 [73, 255]
RA-ILD	3040	1777	58.5	1798	1018	56.6	128 [67, 235]
SSc-ILD	1066	618	58.0	482	248	51.5	125 [74, 246]
MCTD-ILD	119	62	52.1	38	18	47.4	72 [61, 338]
No underlying diagnosis	313	153	48.9	237	109	46.0	145 [61, 275]
Multiple underlying diagnoses	404	240	59.4	204	119	58.3	111 [58, 219]
Exposure-related ILD	692	481	69.5	419	284	67.8	133 [65, 232]
Hypersensitivity pneumonitis	455	346	76.0	190	141	74.2	109 [63, 232]

Percentages are shown for the overall cohort (incident and existing fibrosing ILD) and for the incident fibrosing ILD cohort only

IIP idiopathic interstitial pneumonia, ILD interstitial lung disease, iNSIP idiopathic non-specific interstitial pneumonia, IQR interquartile range, MCTD mixed connective tissue disease, RA rheumatoid arthritis, SSc systemic sclerosis

*Patients in the existing fibrosing ILD cohort could have existing or incident progression, while patients in the incident fibrosing ILD cohort could have incident, but not existing, progression (diagnosed by proxies). Most patients with incident progression were from the incident fibrosing ILD cohort (13,518/14,722, 91.8%)

^†Time to progression was calculated from the first of the two claims that were required to establish a diagnosis of incident fibrosing ILD to the time of the claim indicating progression