Four-meter gait speed predicts mortality in IPF

SAN DIEGO – Among patients with idiopathic pulmonary fibrosis (IPF), an improvement in 4-meter gait speed with pulmonary rehabilitation is an independent predictor of all-cause mortality at 1 year, suggest results from a multicenter study presented at an international conference of the American Thoracic Society.

The authors of the study found that patients who improved their gait speed had a longer survival time. In all, 11% of patients died within 1 year of completing pulmonary rehabilitation.

Doug Brunk/MDedge News

“Mortality is an attractive endpoint in IPF clinical research but requires large sample sizes and long follow-up duration, making clinical trials expensive and challenging to undertake,” lead study author Claire M. Nolan, MSc, said at the conference.

“Consequently, there is much interest in surrogate endpoints of mortality. In the elderly population, a lot of work has been done on performance measures, in particular the 4-meter gait test. It’s a simple test to do from the assessor’s perspective, because you just need a 4-meter corridor and a stopwatch. From the patient’s perspective, they only have to walk at their usual speed, making it feasible in most settings.”

The study by Ms. Nolan, a National Institute for Health Research fellow, and her associates, involved recruiting 90 IPF patients referred to three outpatient pulmonary rehabilitation programs in London. All patients underwent the following assessments before and after 8 weeks of pulmonary rehabilitation: spirometry; Medical Research Council dyspnea score; anthropometry; 4-meter gait speed; incremental shuttle walk test, and King’s Brief Interstitial Lung Disease questionnaire. Ms. Nolan, a respiratory physiotherapist with the Harefield Pulmonary Rehabilitation and Muscle Research Group, Royal Brompton and Harefield NHS Foundation Trust, Harefield, London, and her associates drew from national databases to obtain data on all-cause mortality 1 year following pulmonary rehabilitation.

“We also identified a cutpoint, so if patients improved their walking speed by 0.009 meters per second or above, that was associated with a longer survival time at 1 year (area under the curve of 0.76, for sensitivity of 69.6% and a specificity of 70%; P less than 0.01),” she said.* “Among patients who achieved that cutpoint or exceeded it, only 5% of them died in the 1-year follow-up period, compared with 23% in the group that didn’t achieve that cutpoint. That’s quite a big difference, but this requires external validation in another population.”

To determine the 4-meter gait speed change cut-off that best discriminated between patients who died and survived, the investigators plotted receiver operating characteristic curves. For validation, they conducted a Kaplan-Meier analysis to assess time to death, with significance assessed via the log-rank test. Finally, they used a multivariate Cox proportional hazards model to characterize the relationship between 4-meter gait speed change and all-cause mortality, adjusting for independent predictors of mortality (age, previous respiratory hospitalizations in the past year, forced vital capacity percent predicted) and baseline 4-meter gait speed.

At baseline, 70% of the 90 patients were male, mean age was 74 years, mean forced vital capacity was 72.8% predicted, and mean Medical Research Council dyspnea score was 3. In addition, mean body mass index was 27.2 kg/m², mean 4-meter gait speed was 0.92 meters per second, mean incremental shuttle walk test measurement was 271 meters, and mean King’s Brief Interstitial Lung Disease total score was 56.4. Following 8 weeks of pulmonary rehabilitation, the patients’ 4-meter gait speed improved significantly by a mean of 0.15 meters per second (P less than .001). All other variables also improved significantly, with the exception of forced vital capacity.

In an interview, Ms. Nolan characterized the results as “one piece of the puzzle in answering whether 4-meter gait speed is a useful test for clinicians and researchers. It needs to be taken in the context of 4-meter gait speed in other populations as well as with what we’re finding in patients with IPF. We know that this test is reliable, valid, and responsive to treatment. Now we know that it has predictive capacity as well.”

During her presentation, she cited potential reasons why change in gait speed is associated with survival. “Firstly, gait speed has been described as a clinical indicator of multisystem well-being and the ‘sixth vital sign,’ ”she said. “Walking ability and speed rely on multiple factors and the integration of many systems, cardiovascular and otherwise. We know that pulmonary rehab has multiple benefits and improves these systems, and it’s plausible that change in gait speed may be a surrogate marker for, say, improvement in exercise capacity or health status. But the precise mechanism requires verification.”

Ms. Nolan acknowledged certain limitations of the study, including the fact that contemporaneous measurement of full lung function testing and pulmonary hypertension diagnosis were not available at the time of the study. “Therefore, we were unable to account for [diffusing capacity of the lung for carbon monoxide] and pulmonary hypertension diagnosis,” she said. “Secondly, we were unable to identify the precise cause of death from the national database of harm and care records, but this corroborates previous data which suggest that it’s difficult to reliably discern if a death is IPF- or non-IPF related. Lastly, we know that the benefits of pulmonary rehab experienced by IPF patients tend to wane after 6 months. It would be interesting to compare the short-term improvements in gait speed that we observed to more sustained improvements, to identify whether this impacts prognostability.”

National Institute for Health Research funded the study. Ms. Nolan reported having no financial disclosures.

*Correction, 5/23/18: An earlier version of this article misstated the 4-meter gait speed cutoff point. 

dbrunk@mdedge.com

SOURCE: Nolan CM et al. ATS 2018, Abstract A2456.

SAN DIEGO – Among patients with idiopathic pulmonary fibrosis (IPF), an improvement in 4-meter gait speed with pulmonary rehabilitation is an independent predictor of all-cause mortality at 1 year, suggest results from a multicenter study presented at an international conference of the American Thoracic Society.

The authors of the study found that patients who improved their gait speed had a longer survival time. In all, 11% of patients died within 1 year of completing pulmonary rehabilitation.

Doug Brunk/MDedge News

“Mortality is an attractive endpoint in IPF clinical research but requires large sample sizes and long follow-up duration, making clinical trials expensive and challenging to undertake,” lead study author Claire M. Nolan, MSc, said at the conference.

“Consequently, there is much interest in surrogate endpoints of mortality. In the elderly population, a lot of work has been done on performance measures, in particular the 4-meter gait test. It’s a simple test to do from the assessor’s perspective, because you just need a 4-meter corridor and a stopwatch. From the patient’s perspective, they only have to walk at their usual speed, making it feasible in most settings.”

The study by Ms. Nolan, a National Institute for Health Research fellow, and her associates, involved recruiting 90 IPF patients referred to three outpatient pulmonary rehabilitation programs in London. All patients underwent the following assessments before and after 8 weeks of pulmonary rehabilitation: spirometry; Medical Research Council dyspnea score; anthropometry; 4-meter gait speed; incremental shuttle walk test, and King’s Brief Interstitial Lung Disease questionnaire. Ms. Nolan, a respiratory physiotherapist with the Harefield Pulmonary Rehabilitation and Muscle Research Group, Royal Brompton and Harefield NHS Foundation Trust, Harefield, London, and her associates drew from national databases to obtain data on all-cause mortality 1 year following pulmonary rehabilitation.

“We also identified a cutpoint, so if patients improved their walking speed by 0.009 meters per second or above, that was associated with a longer survival time at 1 year (area under the curve of 0.76, for sensitivity of 69.6% and a specificity of 70%; P less than 0.01),” she said.* “Among patients who achieved that cutpoint or exceeded it, only 5% of them died in the 1-year follow-up period, compared with 23% in the group that didn’t achieve that cutpoint. That’s quite a big difference, but this requires external validation in another population.”

To determine the 4-meter gait speed change cut-off that best discriminated between patients who died and survived, the investigators plotted receiver operating characteristic curves. For validation, they conducted a Kaplan-Meier analysis to assess time to death, with significance assessed via the log-rank test. Finally, they used a multivariate Cox proportional hazards model to characterize the relationship between 4-meter gait speed change and all-cause mortality, adjusting for independent predictors of mortality (age, previous respiratory hospitalizations in the past year, forced vital capacity percent predicted) and baseline 4-meter gait speed.

At baseline, 70% of the 90 patients were male, mean age was 74 years, mean forced vital capacity was 72.8% predicted, and mean Medical Research Council dyspnea score was 3. In addition, mean body mass index was 27.2 kg/m², mean 4-meter gait speed was 0.92 meters per second, mean incremental shuttle walk test measurement was 271 meters, and mean King’s Brief Interstitial Lung Disease total score was 56.4. Following 8 weeks of pulmonary rehabilitation, the patients’ 4-meter gait speed improved significantly by a mean of 0.15 meters per second (P less than .001). All other variables also improved significantly, with the exception of forced vital capacity.

In an interview, Ms. Nolan characterized the results as “one piece of the puzzle in answering whether 4-meter gait speed is a useful test for clinicians and researchers. It needs to be taken in the context of 4-meter gait speed in other populations as well as with what we’re finding in patients with IPF. We know that this test is reliable, valid, and responsive to treatment. Now we know that it has predictive capacity as well.”

During her presentation, she cited potential reasons why change in gait speed is associated with survival. “Firstly, gait speed has been described as a clinical indicator of multisystem well-being and the ‘sixth vital sign,’ ”she said. “Walking ability and speed rely on multiple factors and the integration of many systems, cardiovascular and otherwise. We know that pulmonary rehab has multiple benefits and improves these systems, and it’s plausible that change in gait speed may be a surrogate marker for, say, improvement in exercise capacity or health status. But the precise mechanism requires verification.”

Ms. Nolan acknowledged certain limitations of the study, including the fact that contemporaneous measurement of full lung function testing and pulmonary hypertension diagnosis were not available at the time of the study. “Therefore, we were unable to account for [diffusing capacity of the lung for carbon monoxide] and pulmonary hypertension diagnosis,” she said. “Secondly, we were unable to identify the precise cause of death from the national database of harm and care records, but this corroborates previous data which suggest that it’s difficult to reliably discern if a death is IPF- or non-IPF related. Lastly, we know that the benefits of pulmonary rehab experienced by IPF patients tend to wane after 6 months. It would be interesting to compare the short-term improvements in gait speed that we observed to more sustained improvements, to identify whether this impacts prognostability.”

National Institute for Health Research funded the study. Ms. Nolan reported having no financial disclosures.

*Correction, 5/23/18: An earlier version of this article misstated the 4-meter gait speed cutoff point. 

dbrunk@mdedge.com

SOURCE: Nolan CM et al. ATS 2018, Abstract A2456.

SAN DIEGO – Among patients with idiopathic pulmonary fibrosis (IPF), an improvement in 4-meter gait speed with pulmonary rehabilitation is an independent predictor of all-cause mortality at 1 year, suggest results from a multicenter study presented at an international conference of the American Thoracic Society.

The authors of the study found that patients who improved their gait speed had a longer survival time. In all, 11% of patients died within 1 year of completing pulmonary rehabilitation.

Doug Brunk/MDedge News

“Mortality is an attractive endpoint in IPF clinical research but requires large sample sizes and long follow-up duration, making clinical trials expensive and challenging to undertake,” lead study author Claire M. Nolan, MSc, said at the conference.

“Consequently, there is much interest in surrogate endpoints of mortality. In the elderly population, a lot of work has been done on performance measures, in particular the 4-meter gait test. It’s a simple test to do from the assessor’s perspective, because you just need a 4-meter corridor and a stopwatch. From the patient’s perspective, they only have to walk at their usual speed, making it feasible in most settings.”

The study by Ms. Nolan, a National Institute for Health Research fellow, and her associates, involved recruiting 90 IPF patients referred to three outpatient pulmonary rehabilitation programs in London. All patients underwent the following assessments before and after 8 weeks of pulmonary rehabilitation: spirometry; Medical Research Council dyspnea score; anthropometry; 4-meter gait speed; incremental shuttle walk test, and King’s Brief Interstitial Lung Disease questionnaire. Ms. Nolan, a respiratory physiotherapist with the Harefield Pulmonary Rehabilitation and Muscle Research Group, Royal Brompton and Harefield NHS Foundation Trust, Harefield, London, and her associates drew from national databases to obtain data on all-cause mortality 1 year following pulmonary rehabilitation.

“We also identified a cutpoint, so if patients improved their walking speed by 0.009 meters per second or above, that was associated with a longer survival time at 1 year (area under the curve of 0.76, for sensitivity of 69.6% and a specificity of 70%; P less than 0.01),” she said.* “Among patients who achieved that cutpoint or exceeded it, only 5% of them died in the 1-year follow-up period, compared with 23% in the group that didn’t achieve that cutpoint. That’s quite a big difference, but this requires external validation in another population.”

To determine the 4-meter gait speed change cut-off that best discriminated between patients who died and survived, the investigators plotted receiver operating characteristic curves. For validation, they conducted a Kaplan-Meier analysis to assess time to death, with significance assessed via the log-rank test. Finally, they used a multivariate Cox proportional hazards model to characterize the relationship between 4-meter gait speed change and all-cause mortality, adjusting for independent predictors of mortality (age, previous respiratory hospitalizations in the past year, forced vital capacity percent predicted) and baseline 4-meter gait speed.

At baseline, 70% of the 90 patients were male, mean age was 74 years, mean forced vital capacity was 72.8% predicted, and mean Medical Research Council dyspnea score was 3. In addition, mean body mass index was 27.2 kg/m², mean 4-meter gait speed was 0.92 meters per second, mean incremental shuttle walk test measurement was 271 meters, and mean King’s Brief Interstitial Lung Disease total score was 56.4. Following 8 weeks of pulmonary rehabilitation, the patients’ 4-meter gait speed improved significantly by a mean of 0.15 meters per second (P less than .001). All other variables also improved significantly, with the exception of forced vital capacity.

In an interview, Ms. Nolan characterized the results as “one piece of the puzzle in answering whether 4-meter gait speed is a useful test for clinicians and researchers. It needs to be taken in the context of 4-meter gait speed in other populations as well as with what we’re finding in patients with IPF. We know that this test is reliable, valid, and responsive to treatment. Now we know that it has predictive capacity as well.”

During her presentation, she cited potential reasons why change in gait speed is associated with survival. “Firstly, gait speed has been described as a clinical indicator of multisystem well-being and the ‘sixth vital sign,’ ”she said. “Walking ability and speed rely on multiple factors and the integration of many systems, cardiovascular and otherwise. We know that pulmonary rehab has multiple benefits and improves these systems, and it’s plausible that change in gait speed may be a surrogate marker for, say, improvement in exercise capacity or health status. But the precise mechanism requires verification.”

Ms. Nolan acknowledged certain limitations of the study, including the fact that contemporaneous measurement of full lung function testing and pulmonary hypertension diagnosis were not available at the time of the study. “Therefore, we were unable to account for [diffusing capacity of the lung for carbon monoxide] and pulmonary hypertension diagnosis,” she said. “Secondly, we were unable to identify the precise cause of death from the national database of harm and care records, but this corroborates previous data which suggest that it’s difficult to reliably discern if a death is IPF- or non-IPF related. Lastly, we know that the benefits of pulmonary rehab experienced by IPF patients tend to wane after 6 months. It would be interesting to compare the short-term improvements in gait speed that we observed to more sustained improvements, to identify whether this impacts prognostability.”

National Institute for Health Research funded the study. Ms. Nolan reported having no financial disclosures.

*Correction, 5/23/18: An earlier version of this article misstated the 4-meter gait speed cutoff point. 

dbrunk@mdedge.com

SOURCE: Nolan CM et al. ATS 2018, Abstract A2456.