TP53 and bronchiolitis obliterans syndrome: In a 2018 study, the addition of a corresponding p53 immunohistochemistry (IHC) staining to 60 examined H&E stained BO biopsy slides as examined by 10 GI pathologists was found to significantly increase both interobserver agreement and diagnostic accuracy (as compared with “gold standard” diagnosis via consensus agreement between five expert BO pathologists) (p = 0.071 and p = 0.0021) [18].