Improvements in physical ability as seen with the incremental shuttle walk test (ISWT) mirror pulmonary function improvements in bronchiectasis patients, a study reports, indicating that the test could serve as a valid tool to measure therapy response in clinical trials.
The study, “Validation of the incremental shuttle walk test as a clinical endpoint in bronchiectasis,” was published in the journal Chest.
Most clinical trials testing the effectiveness of bronchiectasis treatments are focused on improvements in pulmonary function and clearance of microbial infections. There is, however, a need to understand the impact therapies have on improving the functional capacity of patients, the researchers said.
The ISWT is a frequently used functional capacity assessment. It tests a person’s ability to walk around two cones set 9 meters apart — so the final track is 10 meters — in time to a set of auditory beeps that get progressively faster; patients walk for as long as they can until they are either too breathless or can no longer keep up with the beeps.
Researchers in this study evaluated the reliability, validity, and ability of the ISWT to indicate disease severity in response to treatment, with the goal of including it as an assessment tool to determine the effectiveness of bronchiectasis therapies.
A total of 30 clinically stable bronchiectasis patients with a mean age of 59.1 years participated in the study. Patients took the test two times, with a period of six months between each test.
In the first test, the patients walked a mean distance of 390 meters, while six months later, they covered a mean distance of 400 meters, revealing no significant change in functional capacity. This result indicates the test’s reliability, according to the researchers.
To test the validity of the ISWT, they compared its results with those of the standard St. George’s Respiratory Questionnaire (SGRQ), a tool used to assess the impact of disease on daily life and overall well-being of patients. The higher the SGRQ score, the greater the severity of the disease.
When the results of 94 patients were compared, researchers observed that the lower the SGRQ score, the better the patient did in the ISWT, indicating a negative correlation between the two tests.
The team found a similar relationship between the ISWT and the Bronchiectasis Severity Index (BSI), which examines patients’ clinical, radiological, and infection-related parameters to determine the severity of the disease. Like the SGRQ, a higher BSI reflects a more severe disease. In 40 bronchiectasis patients, researchers found that the longer the distance walked in the ISWT, the lower the patients’ BSI.
Similarly, they found that the longer patients spent inactive, or sedentary, the more their ISWT distance was decreased, while increased physical activity markedly improved the distance they could cover in the ISWT.
As a result of comparing ISWT data with that of standard disease severity scoring tools, the researchers established the validity of the ISWT.
Concerning the responsiveness of the test, the team initially analyzed data from 30 patients who received antibiotics intravenously for an episode of disease exacerbation. Patients were evaluated at the beginning and after 14 days of treatment to assess their condition and the effectiveness of the treatment.
In addition to the ISWT, pulmonary function was also assessed by measuring forced vital capacity.
Researchers found a marked improvement in the patients’ mean distance walked in the ISWT after 14 days of therapy (335 meters) compared with the start of the treatment (265 meters). These results correlated with an improvement in pulmonary function.
Similarly, in 94 patients who received oral antibiotics for exacerbation treatment, the researchers reported a 16.3% improvement in the distance walked in the ISWT over the start of the treatment, which mirrored the positive outcomes observed in other tests.
Researchers also assessed data from a previously published study in which 65 patients received either nebulized gentamicin (an antibiotic) or a placebo. After 12 months of treatment, these patients could cover 34.7% more distance in the ISWT test compared with those on a placebo.
Statistical analysis revealed that an improvement of 5% on the ISWT would be able to indicate therapy effectiveness with 92% sensitivity and 50% specificity.
The team concluded that the ISWT is “reliable, valid and additionally, responsive to therapy (both short-term and long-term) in a large cohort of patients with bronchiectasis and therefore supports its use as an objective clinical endpoint that represents functional capacity.”
They propose a minimum clinically relevant difference of 5% improvement in the ISWT as an objective endpoint in clinical trials to assess the effectiveness of therapies in bronchiectasis patients.