Metodologias laboratoriais para o diagnóstico de hemoglobinas variantes / The laboratory methodology for diagnosis of hemoglobin variants

Among the electrophoretical methodologies for hemoglobin examinations under different experimental conditions, isoelectrofocusing and high performance liquid chromatography are the most frequently used for the detection of hemoglobin variants. Moreover, molecular techniques are also developed in many laboratories. The correct laboratorial diagnosis of hemoglobin alterations is especially important for the interactive forms principally in Brazil, because of the many associations of hemoglobin alterations and variants with co-migration. The association of classical and molecular techniques is essential for accurate identification of hemoglobin variants.

Contribuição do estudo molecular de hemoglobinas S-like para o conhecimento da diversidade genética da população brasileira: [carta ao editor] / The contribution of molecular studies of S-like hemoglobins to knowledge of the genetic diversity of the Brazilian population: [letter to editor]

Over 900 hemoglobin variants have already been described, withmore than 100 having electrophoretic migration similar to Hb S inalkaline pHs. In the analysis of 98 samples that presented with thismigration pattern, Hb D-Los Angeles in heterozygosis was prevalentand associations with Hb S and Hb Lepore were identified, apreviously unpublished fact and with beta-thalassemia, which isalso rare. In addition, carriers of Hb Korle-Bu and Hb Hasharonwere found amongst other hemoglobinopathies. This heterogeneityreflects the special colonization conditions and the high racialadmixture in Brazil. The correct laboratorial diagnosis is veryimportant for hemoglobinopathy carriers because of the manyassociations of hemoglobin alterations and the variants with comigration.An accurate identification of hemoglobin variants isessential for genetic counseling and appropriate therapy.

Avaliação eletroforética, cromatográfica e molecular da Hb D Los Angeles no Brasil / Electrophoretical, chromatographic and molecular valuations of Hb D Los Angeles in Brazil

A variante de hemoglobina (Hb) D mais comum, Hb D Los Angeles ou D Punjab, é originada de uma transversão GAA->CAA no códon 121 da globina beta; essa mutação resulta na substituição do ácido glutâmico por glutamina na proteína. É a terceira variante de hemoglobina mais freqüente da população brasileira. Como as hemoglobinas D apresentam migração similar à hemoglobina S em pH alcalino, e com a hemoglobina A em pH ácido, são necessários vários testes para o correto diagnóstico. No presente estudo objetivou-se relacionar os diferentes procedimentos laboratoriais de rotina diagnóstica, além da análise molecular, para estabelecer o perfil de Hb D Los Angeles no Brasil. Foram analisados 47 indivíduos da população brasileira com provável Hb D Los Angeles, por vários procedimentos eletroforéticos em diferentes condições de pH, além da cromatografia líquida de alta pressão, e testes moleculares para confirmação da mutação. Foram encontrados quatro tipos de combinações de hemoglobinas: 42 indivíduos portadores de hemoglobina AD Los Angeles, dois indivíduos com doença de Hb S/D Los Angeles, dois indivíduos com Hb D Los Angeles e talassemia beta e um indivíduo com Hb D Los Angeles e Hb Lepore. Os indivíduos heterozigotos para D Los Angeles são assintomáticos, entretanto, em associação com outras variantes e talassemias podem apresentar graus variáveis de manifestações clínicas. Os resultados apresentados enfatizaram a necessidade da associação de várias metodologias para a identificação da Hb D Los Angeles, além de auxiliar na elucidação de combinações raras

The most common Hb D variant, the Hb D-Los Angeles,also know as Hb D-Punjab, originates through aGAA¨CAA change at the 121 codon of the ƒÀ globingene; this mutation results in the replacement ofglutamic acid for glutamine in the protein. It is thethird most common hemoglobin variant in theBrazilian population. This variant has electrophoreticmigration in alkaline pHs similar to Hb S and identicalmigration to hemoglobin A in acidic pHs. Thus, severaltechniques are necessary for its correct diagnosis. Thepurpose of this work was to relate the differentlaboratorial techniques and molecular analyses to determinethe profile of Hb D Los Angeles in Brazil. Fortysevenindividuals from the Brazilian population withHb D Los Angeles were studied. Multiple electrophoresisin several experimental conditions were carried out,in addition to high performance liquid chromatography (HPLC) and molecular analysis to confirm thismutation. Four compound heterozygotes were observed:42 individuals heterozygous Hb AD Los Angeles, twowith Hb S/D Los Angeles disease, two individuals withHb D Los Angeles and beta-thalassemia and one withHb D Los Angeles and Hb Lepore. The heterozygoushemoglobin D Los Angeles is asymptomatic, even thoughits association with other variants and thalassemias maypresent varying degrees of clinical manifestations. Theresults presented emphasize the significance of theassociation of different laboratorial techniques for DLos Angeles diagnosis, and help to elucidate rarecombinations.