Abnormal hemoglobin HbS hemoglobin SNOMEDCT_US:50095005 UMLS:C0019043 Presence of an abnormal type of hemoglobin characterized by the substitution of a glutamic acid residue at position 7 following the initial methionine residue by a valine (the mutation causative of sickle cell disease). The mutation promotes the polymerization of the HbS under conditions of low oxygen concentration. HbS can be identified by multiple methodologies including hemoglobin electrophoresis and high-performance liquid chromatography.