KRT81 and Patent ductus arteriosus: The two-marker combination identified the QM-PDA (KRT81+/HNF1A–) subtype, which was associated with the shortest survival; the Exocrine-like (KRT81–/HNF1A+) subtype which was associated with the longest survival; and the Classical (KRT81–/HNF1A–) subtype, which was associated with intermediate survival (Noll et al., 2016).