Association of the three-minute step test with the occurrence of pulmonary exacerbations in children with cystic fibrosis: a cross-sectional study.

Background: Cystic fibrosis (CF) patients experience pulmonary exacerbations and the three-minute step test (3-min step test) may be a simple and easy-to-perform functional test to help identify such episodes. The present study aimed to evaluate the association of the 3-min step test with the occurrence of pulmonary exacerbations in children with CF.

Methods: Cross-sectional study of CF patients aged 6 years and older. Pulmonary exacerbations were assessed using both the Fuchs criteria and the Kanga Score. The 3-min step test was performed using a 15 cm-high step and heart rate (HR), oxygen saturation (SpO2), and dyspnea were measured before and after the test. Correlations between the test and the scores, as well as comparisons between patients experiencing or not an exacerbation, were performed.

Results: Sixty-two patients (11.1±4.3 years) were included. Both the Fuchs criteria and the Kanga score correlated significantly with age, forced expiratory volume in the first second (FEV1), final SpO2, and 1-min recovery SpO2. A fall greater than 4% in the final SpO2 was significantly associated with the presence of a pulmonary exacerbation, considering both Fuchs and Kanga criteria. Age, resting HR, and HR after 1-min recovery were significantly higher, while FEV1, SpO2 at rest, final SpO2, and SpO2 after 1-min recovery were significantly lower in patients classified as exacerbated.

Conclusions: Physiological responses to the 3-min step test are associated with the occurrence of pulmonary exacerbation in children with CF. Desaturation at the end of the test or during 1-min recovery may be the best variable to monitor.