Several trials in which patients had a capsule‐sponge followed by an endoscopy (totalling > 2000 procedures) show that CS is well‐tolerated and TFF3 immunohistochemical biomarker identifies BO with accuracy (80%–89% sensitivity and 92% specificity) [8, 9, 10, 11]. The gene discussed is TFF3; the disease is bronchiolitis obliterans syndrome.