TABLE 1.

Assessment of immortal time bias (ITB) in published studies reporting effects of antifibrotic therapy on survival of participants with idiopathic pulmonary fibrosis (IPF).

References	Country	ITB checklist*					Presence of ITB	Statistical methods
		C1	C2	C3	C4	C5
Hosein et al. (40)	Canada	No	NA	NA	NA	No	NA	NA
Jo et al. (19)	Australia	Yes	Yes	No	Yes	No	Yes	Time-fixed
Margaritopoulos et al. (43)	Greece	Yes	Yes	No	Yes	No	Yes	Time-fixed
Zubairi et al. (48)	Pakistan	Yes	Yes	No	No	No	Yes	Time-fixed
Cerri et al. (36)	Italy	No	NA	NA	Yes	No	NA	NA
Dempsey et al. (16)	USA	Yes	Yes	No	Yes	No	Yes	Exclusion
Fernández-Fabrellas et al. (39)	Spain	Yes	Yes	No	No	No	Yes	Time-fixed
Kaunisto et al. (42)	Finland	Yes	Yes	No	Yes	No	Yes	Time-fixed
Zurkova et al. (48)	Czech Republic	Yes	Yes	No	Yes	No	Yes	Exclusion
Kang et al. (41)	South Korea	Yes	Yes	No	Yes	No	Yes	Exclusion
Adegunsoye et al. (18)	USA	Yes	Yes	No	Yes	No	Yes	Time-fixed
Alhamad et al. (35)	Saudi Arabia	Yes	Yes	No	Yes	No	Yes	Time-fixed
Behr et al. (17)	Germany	Yes	Yes	No	Yes	No	Yes	Exclusion
Dhooria et al. (37)	India	Yes	Yes	No	Yes	No	Yes	Time-fixed
Feng et al. (38)	China	Yes	Yes	No	Yes	No	Yes	Time-fixed
Moon et al. (44)	South Korea	Yes	Yes	No	Yes	No	Yes	Time-fixed

*The ITB Study Assessment Checklist; ITB: immortal time bias; IPF: idiopathic pulmonary fibrosis; NA: not applicable.

C1: Does study report cohort entry time–point for both intervention and comparator groups.

C2: Does immortal time exit in this study.

C3: Does study report intervention eligibility period for the intervention group.

C4: Does study report observation period for all groups.

C5: Does study report appropriate statistical methods (time–dependent or landmark methods) to address immortal time bias.