[Biological diagnosis of hemoglobinopathies by phenotype analysis]

Haemoglobinopathies are defined by the presence of qualitative and/or quantitative globin chains abnormalities. In most cases, laboratory diagnosis relies on phenotype analysis. Ethnic group, clinical data, complete blood count in absence of recent blood transfusion, iron status, should be taken into account for the diagnosis. Electrophoresis using an alkaline pH buffer system is used as an initial technique for the detection of haemoglobin variants, showing abnormal bands as compared with reference samples. Isoelectric focusing is more resolutive and could be preferred for this reason: If the migration pattern differs from normal, additional confirmatory tests, as citrate agar electrophoresis (acid pH), are required. Relative amounts of variant haemoglobin (Hb A2, F and S...) are quantified using chromatographic methods. Other tests, such as solubility tests, stability tests, Kleihauer-Betke test, are useful in specific cases. The diagnosis relies on clinical and laboratory findings. In the Paris area, the most common variant is Hb. S. Taalassemia traits are also very common. Screening of SS. S beta D. SO Arab, SD Punjab, SC, or thalassaemia major should be made early so that patients found to have one of these varieties should be referred to haemoglobinopathy centers.