Incremental Shuttle Walk Distance Test May Help Detect Early PH, Study Reports

Patricia Inácio, PhD avatar

by Patricia Inácio, PhD |

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An easy and simple tool called the incremental shuttle walk distance test, or ISWD, appears promising to identify early signs of pulmonary hypertension (PH), according to a new study.

The results showed that patients with early PH who don’t show major disease symptoms already have a significant decrease in their exercise capacity, which is evaluated in the ISWD test.

The study, “Incremental Shuttle Walking Test Distance Is Reduced in Patients With Pulmonary Hypertension in World Health Organisation Functional Class I,” was published in the journal Frontiers in Medicine.

Despite the fact that an early diagnosis of PH leads to better patient outcomes, the disease is often diagnosed when patients are in advanced stages. So there is obviously a need to develop better strategies for earlier diagnoses and for screening patients at higher risk, such as those with systemic sclerosis, an autoimmune disease affecting connective tissues in the body.

International guidelines for PH screening highlight the need for performing an echocardiogram, an exam that uses sound waves to produce images of the heart. But this method has limitations, especially in newly diagnosed PH patients.

Also, previous results from the international DETECT study (NCT00706082) — which looked at potential biomarkers in systemic sclerosis patients with suspected PH — showed that some biomarker candidates had no prognostic value for detecting early signs of PH, including the 6-minute walking test (which assesses exercise capacity and endurance by measuring the distance covered over a period of six minutes).

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Now, a team of researchers investigated whether the exercise capacity of patients with newly diagnosed pulmonary hypertension with few or no symptoms was compromised. The team used the ISWD test to address this question.

In the ISWD test, patients are to walk as long as possible around a course that measures 10 meters, walking in time to a set of auditory beeps. Initially, the signals — and therefore the walking speed — is very slow, then it progressively increases. Patients walk for as long as they can until they are either breathless or can no longer keep up with the auditory signals. The number of times, or shuttles, around the 10-meter course is recorded.

The team analyzed data from the ASPIRE registry, which includes patients diagnosed with PH by cardiac catheterization between 2001 and 2010 and who underwent ISWD and lung function tests.

In total, they analyzed data from 895 PH patients with differences in functional capacity, according to the WHO classification system. At diagnosis, nine people were in WHO functional class 1 (which refers to patients who do not experience symptoms while exercising or at rest); 162 in WHO functional class 2 (defined as no symptoms at rest, but patients feel uncomfortable and have shortness of breath doing ordinary activities); 592 patients in WHO functional class 3, and 132 were in WHO class 4.

Patients in WHO classes 3 and 4 were in more advanced stages of the disease.

Researchers found that ISWD results correlated well with the patient’s exercise capacity, and suggested that “exercise capacity is more sensitive than measurements of gas transfer made at rest in identifying patients with pulmonary hypertension in WHO [classes] I and II.”

Patients in WHO class 1 had a significant reduction in exercise capacity, despite the absence of PH symptoms. Compared to patients in WHO class 1, those in class 2 had a lower ISWD.

The results show that patients with newly diagnosed pulmonary hypertension without major symptoms already show significant reduction in exercise capacity, which is detected by the simple ISWD test.

“Data from this study suggest [the ISWD test] might be suited to detecting early disease,” researchers wrote.

Additional studies are required “to assess whether the incremental shuttle walking test could be used as a first line investigation or as part of a battery of tests to screen at-risk patients, proceeding to more complex testing if abnormal,” they added.

A Conversation With Rare Disease Advocates