Introduction: The gold standard for physical activity (PA) measurement is the accelerometer. Its availability is limited. Our objective is to describe PA in idiopathic pulmonary fibrosis (IPF) using the IPAQ-SF (International Physical Activity Questionnaire-Short Form) and to compare it with the accelerometer.

Method: PA was measured using the IPAQ-SF and an accelerometer. Lung function and exercise capacity were evaluated. Both instruments were compared with concordance (Bland-Altman graphs) and correlation analysis (Spearman) between PA parameters and clinical variables.

Results: 40 patients with IPF were included. 75% males, with a mean age of 71 years. Mean FVC and DLco(%pred.) were 79(19) and 45%(14), and the distance walked in the six-minute walk test (6MWT) was 452(93)m. In the IPAQ-SF, patients reported a median(p25-p75) of 420(304-630) mins/week of walking time (WT), 35 mins/week(0-274) of moderate-vigorous PA(MVPA) and 420 mins/day (300-480) of sedentary time (ST). The accelerometer showed 5116(3350-7775) steps/day, 351 mins/week (225-743) of MVPA and 730 mins/day(691-759) of ST. The Bland-Altman graphs evidenced an underestimation of MVPA and ST with the IPAQ-SF compared to the accelerometer, being less marked in sedentary patients. A positive correlation was observed between steps/day and WT in the IPAQ-SF (r=0.348,p=0.038) and an inverse correlation between steps/day and ST in the IPAQ-SF (r=-0.338,p=0.047). Likewise, an inverse correlation was found between ST in the IPAQ-SF and FVC and minimum SpO2 in the 6MWT (r=-0.338,p=0.047 and r=-0.368,p=0.029).

Conclusion: The IPAQ-SF underestimates MVPA and ST compared to the accelerometer. Steps/day were correlated with WT and ST measured by the IPAQ-SF.