Hemoglobinopatias em Portugal e estratégias de Prevenção: Contributo do laboratório de Hematologia e Bioquímica

The hemoglobinopathies are inherited monogenic autosomal recessive disorders resulting from mutations affecting genes responsible for synthesis of the globin chains of haemoglobin, or their regulatory regions. They can be classified, into two main groups: the thalassemias resulting from reduced or no synthesis of one or more globin chains and the haemoglobin variants arise from an alteration in the globin protein structure. Sickle-cell disease and β-thalassemia are the most common human monogenic diseases and represent a serious public health problem in many regions of the world. The most effective way to control this disease is prevention through the detection and identification of carriers of hemoglobinopathies, genetic counselling of couples at risk, and when necessary, the provision of prenatal diagnosis. To be aware the prevalence of hemoglobinopathies in Portugal several studies were conducted. The results indicated that the prevalence is about 2% 1,2,3. The highest prevalence (more than 5%) was observed in the Mira River Basin and the Western Algarve (Barlavento) for carriers of β-thalassemia, and in Coruche, Alcácer do Sal (lower courses of the rivers Tejo and Sado) for carriers of Hb S 1,2. The hemoglobinopathies laboratory performs the diagnosis screening and confirmation in collaboration with Public Health Laboratories and other health care entities, in order to prevent the onset of severe forms of hemoglobinopathies. Hemoglobinopathies are possibly unique amongst all genetic diseases in that which carriers identification is possible (and preferable) by haematological (biochemical) tests rather than DNA analysis. Variant haemoglobins of clinical relevance are Hb S, Hb DPunjab, Hb C, Hb E, Hb Lepore e Hb OArab, since they confer greater risk when associated with other specific alleles 4. Presumptive identification of haemoglobin variants requires performing a minimum of two techniques based on different principles. The MCH below 27 pg and the Hb A2 above 3.5 % make the β thalassemia trait diagnosis. The screening is directed to detect carriers of thalassemia and haemoglobin variants. To do so, we use first line methods, the red cell indices (with morphology) and isoelectric focusing of haemoglobin. The second line tests involve chromatographic techniques, including the study of globin chains by reversed-phase high-performance liquid chromatography (HPLC-RP) and functional tests such as the solubility test for Hb S. HPLC-RP of human globin chains is an important tool in phenotype study of haemoglobin disorders for the detection and presumptive characterization of haemoglobin variants. It was found to be of special value to detect neutral variants. The cases diagnosed by the laboratory between 2010 and 2013 indicate that β-thalassemia and Hb S trait are the most frequent observed. The regions of Algarve, Alentejo and Lisbon, still are the main origin of hemoglobinopathies. Nevertheless it has been detected several cases in the northern region (including β-thalassemia and Hb Lepore). Furthermore the relatively recent population migration, particularly from Brazil and Eastern Europe (where for example the variant Hb OArab is frequent 5) make us expected that the detection of hemoglobinopathies will be a problem not exclusively restricted to certain regions, and should therefore be considered across all country 6. Also concerning prevention, the INSA laboratory promotes health care professional training/education, bearing in mind the promotion of quality results, improvement in performance and in last direct benefit to the population