Prognostic value of 6-min walk test (6MWT) outcomes in patients with interstitial lung disease (ILD) from real-world studies and clinical trials
| Patient population | 6MWT outcomes associated or not associated with poorer prognosis (reduced survival unless otherwise stated) |
| Real-world studies | |
| Patients with ILD (n=62) [30] | Associated: impaired chronotropic response to 6MWT (peak heart rate minus resting heart rate of ≤20 beats·min−1) Not associated (in multivariate models): 6MWD and reduced nadir SpO2 |
| Patients with IPF (n=76) [33] | Associated: abnormal HRR1¶ Not associated (in multivariate models): shorter 6MWD (per 3.05 m) |
| Patients with IPF (n=70) [34] | Associated: shorter 6MWD (<330 m versus ≥330 m or <70% predicted versus ≥70% predicted) |
| Patients with IPF (n=44) [35] | Associated: shorter 6MWD (<212 m) and increased 6MWD decline over 12 months (in the 29 patients with 12 months of follow-up) |
| Patients with IPF (n=81) [36] | Associated: shorter 6MWD (≤300 m), increased oxygen desaturation and reduced distance-saturation product (when comparing mean values for survivors versus nonsurvivors at 12 months) |
| Patients with IPF on a lung-transplant waiting list (n=454) [37] | Associated: shorter 6MWD (<207 m; assessed as a categorical variable) |
| Patients with IPF (n=197) [38] | Associated: oxygen desaturation (SpO2 ≤88%) Not associated (in multivariate models): 6MWD (assessed as a categorical or continuous variable) |
| Patients with UIP or NSIP (n=105) [39] | Associated: oxygen desaturation (SpO2 ≤88%) Not associated: 6MWD (per 3.05 m) |
| Patients with fibrotic IIP (n=30) [40] | Associated: increased oxygen desaturation and SpO2 ≤88% Not associated: 6MWD |
| Patients with IPF (n=93) [41] | Associated: reduced nadir SpO2 and nadir SpO2 <88% Not associated (in multivariate models): 6MWD |
| Patients with interstitial pneumonia (n=73) [42] | Associated (with increased rehospitalisation for respiratory-related events): reduced SpO2 recovery index+ and HRR1¶ Not associated (with increased rehospitalisation for respiratory-related events in multivariate models): 6MWD, nadir SpO2, change in SpO2, SpO2 1 min after 6MWT and modified Borg scale |
| Clinical trials | |
| Patients with IPF from the placebo arms of the phase 3 CAPACITY trials (n=338) [13] | Tended to have higher mortality risk (not statistically significant): shorter 6MWD at baseline (<250 m or 250–349 m versus ≥350 m) and 6MWD decline of ≥50 m (versus 6MWD decline of <50 m) at 24 weeks |
| Patients with IPF from the placebo and interferon-γ arms of the phase 3 INSPIRE trial (n=822 and n=748, respectively) [43, 44]# | Associated: 6MWD of <250 m (versus ≥350 m) at baseline and 6MWD decline of 26–50 m or >50 m (versus 6MWD decline of ≤25 m) at 24 weeks Not associated: 6MWD of 250–349 m at baseline |
IPF: idiopathic pulmonary fibrosis; UIP: usual interstitial pneumonia; NSIP: nonspecific interstitial pneumonia; IIP: idiopathic interstitial pneumonia; 6MWD: 6-min walk distance; SpO2: peripheral oxygen saturation; HRR1: heart rate recovery after 1 min. #: analysis of outcomes in INSPIRE revealed no evidence of a treatment effect; therefore, these analyses included data from both treatment arms to maximise study power. One analysis included patients who completed the 6MWT at the baseline visit (n=822) and the other included patients who had both a baseline and week 24 visit (n=748). ¶: heart rate at the end of the 6MWT minus heart rate at 1 min after completion of the 6MWT; defined as abnormal if ≤13 beats. +: oxygen saturation recovery after the 6MWT.