Diagnostic approach to hemoglobinopathies

Abnormalities of hemoglobin (Hb) synthesis are among the most common inherited disorders of man and can be quantitative (thalassemia syndromes) or qualitative (variant Hbs). Definite identification of hemoglobinopathies can be achieved by a stepwise algorithmic approach, starting with a detailed clinical history, through hematologic evaluation [complete blood count (CBC)], reticulocyte count, red blood cell (RBC) morphology], protein based analytic methods [Hb electrophoresis or isoelectric focusing (IEF), cation exchange high performance liquid chromatography (HPLC), reversed phase HPLC] to nucleic acid based methods [such as polymerase chain reaction (PCR), reverse transcribed (RT)-PCR, sequencing of genomic DNA and sequencing of RT-PCR amplified globin cDNA of the gene of interest]. When an abnormality of Hb function (increased or decreased oxygen affinity) or stability (unstable Hb variants) is suspected from the phenotype, special confirmatory tests (determination of p50, Heinz body prep and isopropanol or heat stability tests) can be useful. Family studies are also helpful in certain cases. A review of the application of these methods to the diagnosis of hemoglobinopathies at the Sickle Cell Center Laboratory in Augusta, GA, USA, is presented below.