Modified 1-min sit-to-stand test for evaluating exercise capacity in pulmonary fibrosis

Abstract

Question The reference test for the functional evaluation of pulmonary fibrosis (PF) during exercise is the 6-min walk test (6MWT). However, the 6MWT involves temporal and spatial constraints that the 1-min sit-to-stand test (1-MSTST) does not have. Previous studies have not validated 1-MSTST use in this context, mainly because of far less oxygen desaturation. We hypothesise that the modified 1-MSTST (m1-MSTST), taking into account the recovery phase, could compensate this shortcoming. Patients and methods This was a randomised, crossover, single-centre trial conducted in 36 patients with PF. A 6MWT and 1-MSTST were performed 30 min apart for each patient in a randomised order. An equivalence test was performed on the peripheral oxygen saturation (SpO2) nadir. Results The 36 patients comprised eight with idiopathic PF, five with nonspecific idiopathic pneumonia, eight with collagen tissue disease-associated PF, four with hypersensitivity pneumonitis, two with sarcoidosis and nine with other PF. Mean±sd nadir desaturation was 84.9±4.3% for the 6MWT and 88±3.5% for the m1-MSTST, with a strong correlation between both tests. 33 patients (91.7%) had concordant results in the two tests regarding significant desaturation (SpO2 delta >4% or nadir <88%), which is a known prognosis factor. Conclusion The m1-MSTST, taking into account the recovery phase, is a sensible compromise to the 6MWT in measuring exercise performance in people with PF. As many clinical endpoints transfer from hospital to outpatient care, the m1-MSTST is technically easier and more practical for patients. Further studies are warranted to determine the minimal clinically important difference and norms in healthy subjects.