From the Journals

Step test signals exercise capacity in asthma patients



The incremental step test is a highly reliable measure of exercise capacity in patients with moderate to severe asthma, based on data from 50 individuals.

Asthma patients often limit their physical exercise to avoid respiratory symptoms, which creates a downward spiral of reduced exercise capacity and ability to perform activities of daily living, wrote Renata Cléia Claudino Barbosa of the University of Sao Paulo and colleagues. “However, exercise training has been shown to be an important adjunctive therapy for asthma treatment that improves exercise capacity and health-related quality of life,” they wrote.

Step tests have been identified as a simpler, less costly alternative to cardiopulmonary exercise tests to measure exercise capacity in patients with chronic obstructive pulmonary disease, but their effectiveness for asthma patients has not investigated, the researchers said.

In a study published in Pulmonology, the researchers recruited 50 adults with moderate or severe asthma during routine care at a university hospital. The participants had been clinically stable for at least 6 months, with no hospitalizations, emergency care, or medication changes in the past 30 days. All participants received short-acting and long-acting bronchodilators and inhaled corticosteroids. The patients ranged in age from 18 to 60 years, with body mass index measures from 20 kg/m2 to 40 kg/m2.

Participants were randomized to tests on 2 nonconsecutive days at least 48 hours apart. On the first day, patients completed asthma control questionnaires and lung function tests, then performed either a cardiopulmonary exercise test (CPET) or two incremental step tests (IST-1 and IST-2). On the second day, they performed the other test. Participants were instructed to use bronchodilators 15 minutes before each test.

The step test involved stepping up and down on a 20-cm high wooden bench.

Overall, the peak oxygen uptakes were 27.6 mL/kg per minute for the CPET, 22.3 mL/kg per minute for the first IST, and 23.3 mL/kg per minute for the second IST.

“The IST with better performance regarding the peak VO2 value was called the best IST (b-IST),” and these values were used for validity and interpretability analyses, the researchers wrote.

In a reliability analysis, the intraclass correlation coefficient (ICC) was 0.93, the measurement error was 2.5%, and the construct validity for peak VO2 was significantly more reliable than the CPET (P < 0.001), the researchers said. The ICC for total number of steps was 0.88.

Notably, “the present study also demonstrated that IST is not interchangeable with the CPET since the subjects with moderate to severe asthma did not reach the maximal exercise capacity,” the researchers said. However, “we believe that the IST is superior to walking tests in subjects with asthma because it is an activity that requires greater ventilation in a subject’s daily life,” they said.

The study findings were limited by several factors including the relatively small study population and the small number of male patients, which may limit generalizability to males with asthma or other asthma endotypes, the researchers said. However, the results were strengthened by the randomized design, and support the value of the IST as a cost-effective option for assessing exercise capacity, preferably with two step tests to minimize the learning effect, they said. Additional research is needed to determine whether IST can assess responsiveness to pharmacological and nonpharmalogical treatments in asthma patients, they noted.

The study was supported by the Sao Paulo Research Foundation, Conselho Nacional de Pesquisa, and Coordination of Improvement of Higher Level Personnel--Brazil. The researchers had no financial conflicts to disclose.

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