Incremental Step Test for Asthma: Reproducibility, Validity, Reliability

In patients with moderate to severe asthma, the incremental step test (IST) provides excellent reliability and validity in assessing exercise capacity without ceiling or floor effects, according to a study published in Pulmonology.

The measurement properties of the IST in adults with asthma had not been previously investigated, although the test has proven reproducible and reliable in patients with COPD, bronchiectasis, acute lung diseases, and pulmonary hypertension, said the study authors. Therefore, researchers sought to investigate the measurement properties of the IST in 50 subjects with moderate to severe asthma recruited from a tertiary university hospital specializing in treating severe asthma.

All subjects performed 1 cardiopulmonary exercise test (CPET) and 2 ISTs in random sequences, with pulmonary gas exchange measured during all exercise tests. The researchers found that peak oxygen uptake (peak VO₂) levels were as follows: for the CPET, 27.6 ml/kg per minute; for the first IST, 22.3 ml/kg per minute; and for the second IST, 23.3 ml/kg per minute. The IST presented excellent reliability (intraclass correlation coefficient=0.93), very good measurement error (2.5%), and construct validity for peak VO₂ measurement compared with the CPET (P <.001) for assessing exercise capacity in subjects with moderate to severe asthma, with appropriate ceiling (10%) and floor (0%) effects.

“Our results demonstrate that the IST showed excellent reproducibility and strong validity in subjects with moderate to severe asthma,” concluded the researchers. “These results suggest that the IST provides a reliable measure of exercise capacity and can be used in clinical practice and research,” they added. However, future studies should be conducted to assess whether the IST is a valid instrument for measuring responsiveness to pharmacological and nonpharmacological treatments in this population.

Reference

Barbosa RCC, Silva RA, Lunardi AC, et al. Reproducibility, validity, and reliability of the incremental step test for subjects with moderate to severe asthma. Pulmonology. Published online February 24, 2022. doi:10.1016/j.pulmoe.2022.02.002