D1.99 - Exploring the relationship between 6 minutes walk test (6MWT) performance and lung function in Severe Asthma and CRSwNP

6-minute walk test (6MWT) is a simple standardized measure of physical performance and functional exercise capacity that reflects the combined function of the lungs, heart, circulation and muscles. To date, there is scant literature investigating 6MWT in asthma. The aim of this study is to investigate if there is a correlation between 6mwt and pulmonary function tests assessed through spirometry in patients with severe asthma and CRSwNP that need a therapeutic step up. 

16 patients were enrolled in this longitudinal prospective study: 5 were at GINA step 5 and required to add a biologic, 11 were at GINA step 4 and moved to GINA step 5 and 8 had severe CRSwNP requiring biologic therapy. We assessed eosinophil counts, ECP, BMI, spirometry and 6MWT at baseline (T0), one month(T1) and three months(T2). Additionally IPAQ (International Physical Activity Questionnaire), ACT and/or SNOT-22 questionnaires were administered. Changes in the variables studied over time were analyzed by the non-parametric paired test.

A statistically significant increase of 6mwt distance was observed between T0 and T1(566m vs 624m, p=0.002), T0 and T2(566m vs 634m, p=<0.001), T1 and T2(624m vs 634m, p=0.017). There was an increase in FEV1(T0 2.91mL vs T2 3.23mL, p=0.372). IPAQ increase is not statistically significant(p<0.05). Using the Spearman test, we investigated whether there is a correlation between distance in 6MWT and different variables.  6MWT(T0) has a fair correlation with FEV1(T0) (Rho=0.443, p=0.050), suggesting a positive relationship. The correlation between 6MWT and FEV1 at T1 and T2 was not significant(p>0.05). The performance in the 6MWT improves independently of respiratory function tests. The 6MWT(T1) showed a significant correlation with ACT(T0) (Rho=0.637, p=0.011), while no significant correlations were observed at other time points(p>0.05). Using linear regression analysis with the predicted variable 6MWT(T1), a significant correlation was observed with sex, BMI, ACT(T0) and IPAQ(T0) score. The same test with the predicted variable 6MWT(T2), this correlation was no longer observed, highlighting how these variables may predict which patients are early responders.

Due to the study's limitations, more research with a larger sample size is needed to confirm our findings and explore the potential of 6MWT as an indicator of therapy response, in severe asthma and CRSwNP patients. Further work towards standardization and its use in asthma should be considered.