Anchor-based estimates of minimal clinically important difference (MCID) for worsening in idiopathic pulmonary fibrosis from current study and comparison with MCID estimates from previous studies

Current MCID estimatePrevious MCID estimate#
Time periodMCID+ (95% CI)Time period [ref.]MCID
6MWD m24 weeks−74.89 (−93.11– −56.66)48 weeks [14]24–45§
48 weeks [16]21.7 –37.0§
52 weeks [11]28
SF-36 physical component score60 weeks−6.79 (−8.66– −4.92)26 weeks [13]3
No specified time period [10]5
Total SGRQ score60 weeks10.95 (7.81–14.1)26 weeks [13]7 (5–10)##
52 weeks [12]4–5
UCSD SOBQ total score60 weeks11.38 (7.83–14.93)24 weeks [19]8 (5–11)##

6MWD: 6-min walk distance; SF-36: 36-Item Short-Form Health Survey; SGRQ: St George's Respiratory Questionnaire; UCSD SOBQ: University of California, San Diego Shortness of Breath Questionnaire. #: previous studies have estimated MCID values for worsening and improvement using both anchor-based and distribution-based methods; : 6MWD met responsiveness criteria only in the Sildenafil Trial of Exercise Performance in Idiopathic Pulmonary Fibrosis (STEP-IPF) cohort, while the SF-36 physical component score, SGRQ and UCSD SOBQ met criteria in only the Prednisone, Azathioprine, and N-Acetylcysteine: A Study That Evaluates Response in Idiopathic Pulmonary Fibrosis (PANTHER-IPF) cohort; therefore, time period for MCID is 24 weeks or 60 weeks; +: MCID for worsening only, since it was calculated as mean change in “somewhat worse” health transition question (SF2) group from baseline to follow-up; §: range; ##: point estimate (range).