Fatigue in idiopathic pulmonary fibrosis measured by the Fatigue Assessment Scale during antifibrotic treatment

Background: Fatigue is a common complaint in patients with idiopathic pulmonary fibrosis (IPF) and has been reported in a considerable percentage of patients. Fatigue is also a registered side effect of pirfenidone, one of two approved antifibrotic drugs. The Fatigue Assessment Scale (FAS) was developed for assessment of fatigue in sarcoidosis and validated in patients with sarcoidosis. FAS has been used in a few IPF studies but has not been validated. Aims: To study the change in FAS after initiation of pirfenidone or nintedanib in the treatment of patients with IPF during a six-month period. Methods: Between April 2017 and January 2018, all incident patients with IPF starting antifibrotic treatment were invited to complete FAS before, four weeks, three, and six months after initiation of antifibrotic treatment. Baseline characteristics including lung function were registered. Results: Fifty-two patients were included, mean FVC% 84.8, mean DLCO% 51.4. Nintedanib was started in 25 patients; 27 patients started pirfenidone. Sixty-four percent of patients had a FAS score >22 indicating substantial fatigue at baseline. There was no statistically significant difference in FAS score for patients treated with nintedanib or pirfenidone at any time point. FAS score increased statistically significantly during the six-month follow-up. This change was driven by patients without substantial fatigue at baseline with an increase in FAS score of 8.4 points; patients with substantial fatigue at baseline experienced no statistically significant change. Conclusion: A majority of patients with IPF suffered from substantial fatigue at the time of diagnosis. Fatigue progressed over time and increasing fatigue was associated with younger age, nintedanib treatment and low degree of fatigue at baseline. There was no significant difference in FAS score between the two antifibrotic treatments at any time point, even though fatigue is not a registered side effect in nintedanib.