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

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.

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 (S _pO ) nadir.

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 (S _pO delta >4% or nadir <88%), which is a known prognosis factor.

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.