Table 4

MID estimates for 6MWD

TimeES=0.5ΔFVC=7–12%ΔSGRQt=5–10Regression equation for FVCRegression equation for SGRQtMean
Baseline to 6 months41.3 m17.4 m*10.8 m

  • Δ6MWD=2.6+1.9 (ΔFVC)

  • Corresponding to 10% change in raw FVC, Δ6MWD=21.6 (8.6–33.6)

  • Δ6MWD=−4 +(−1.2)(ΔSGRQt)

  • Corresponding to 7 unit change in SGRQt, Δ6MWD=12.4 (5.4–19.4)

20.7
6–12 months58.5 m40.2 m*22.5 m

  • Δ6MWD=−6.1+2.9(ΔFVC)

  • Corresponding to 10% change in raw FVC, Δ6MWD=22.9 (6.9 to 39.9)

  • Δ6MWD=−1.9 +(−4.4)(ΔSGRQt)

  • Corresponding to 7 unit change in SGRQt, Δ6MWD=32.7 (25 to 41.1)

35.4

  • Grand mean=28, thus MID=28 m.

  • The 95% CIs around the MID estimates from the regression equations are sample size dependent. The point estimates should be viewed as the best estimates of the MID.

  • ↵* Weighted mean of subjects whose raw FVC changed by 7–12% over the indicated time interval.

  • ES, effect size; FVC, forced vital capacity; MID, minimum important difference; 6MWD, 6 minute walk distance; SGRQt, Saint George's Respiratory Questionnaire SGRQ Total.