Summary of available data for the FSS total score. FSS total score was based on the mean of the 9-item score. If the number of missing items was <4, the FSS total score was the mean of the non-missing items; if 4 or more items were missing, the total score was set to missing. The PILLAR study was the first simeprevir trial to include PRO endpoints. Sites that enrolled the first patients did not have appropriate language translations of the PRO instruments for their patients to complete at their baseline visit, hence the low patient numbers at baseline in PILLAR (n = 245). Some of these patients subsequently completed PRO instruments at post-baseline visits. BL baseline, FSS Fatigue Severity Scale, ITT intent to treat, PRO patient-reported outcome.