Supplementary Material for: Additional upfront thoracic ultrasound in the workup of patients with unilateral pleural effusion: A prospective observational pilot study.

Abstract: Background: In patients with pleural effusion, specific ultrasound characteristics are associated with pleural malignancy. Objectives: This study aims to evaluate the added value of an additional, up-front, systematic thoracic ultrasound (TUS) to standard imaging in patients with unilateral pleural effusion of unknown cause in a clinical setting. Methods: In a prospective observational pilot study, patients referred for work-up and thoracentesis of a unilateral pleural effusion received up-front TUS following a set protocol in addition to available imaging and US guiding the thoracentesis or diagnostic puncture. The primary outcome was the proportion of cases where systematic TUS changed the planned diagnostic work-up. Follow-up took place 26 weeks after inclusion. Results: From February to December 2020, 55 patients were included. Thirty-six (65%) patients had other chest imaging available before TUS. Twenty-one (38%) were diagnosed with malignant pleural effusion. Three patients (5%) had clinically relevant changes in the diagnostic work-up after additional systematic TUS. Conclusions: Additional up-front, systematic TUS had limited clinically relevant effect on the planned diagnostic work-up in patients with unilateral pleural effusion in a setting where chest CT scans often are available at referral.