Hb O-Tibesti [beta121(GH4)Glu-->Lys; beta11(A8)Val-->Ile], a hemoglobin variant carrying in the same beta chain the substitutions of Hb O-Arab and Hb Hamilton, found in combination with Hb S [beta6(A3)Glu-->Val]

Pitfalls in the genetic diagnosis of Hb S

Patients homozygous for Hb S need to be properly identified to start as early as possible a treatment that should avoid complications. For prevention and genetic counseling, carriers of Hb S have to be screened. Hb S is easily detected by several analytical systems, but other variants, usually harmless, may behave as Hb S, leading to false positive diagnosis. Some interactions may also cause difficulties in the qualitative or quantitative interpretation of a chromatography or electrophoresis profile. These problems may result from several causes among which the simultaneous presence of an α chain variant leading to the formation of tetramers having both an α and a β chain modified, the presence of a second mutation within the Hb S allele, the existence of a compound heterozygous state leading to some "Hb S trait with dominantly transmitted sickle cell disease (SCD)", and the presence of thalassemic allele affecting the intracellular proportion of Hb S. In case of any "dominant Hb S trait" a thorough Hb study is always required. This work reports some of the difficulties observed by us, or reported in the literature, and propose how to avoid them and reach a correct diagnosis.

Globin chain analysis by reversed phase high performance liquid chromatography: recent developments

Reversed phase high performance liquid chromatography of globin chains is an important additional tool in the study of hemoglobin abnormalities. Using a technique modified from that of Leone et al.,[1] we report here the relative chromatographic behavior of about 200 different hemoglobin variants. This method provides an additional dimension in the presumptive characterization of hemoglobin variants. It was also found to be of special value for measuring the expression of neutral variants, such as thalassemic or unstable hemoglobins, and to identify neutral mutations associated with another variant, resulting in unusual hematological presentations.