Thalass. Rep., Volume 2, Issue 1 (June 2012) – 4 articles

The Laboratory for Molecular Prenatal Diagnosis of Hemoglobinopathies at the Villa Sofia-Cervello Hospital in Palermo, Italy, carries out an intensive screening program aimed at identifying the healthy carriers of thalassemia and, consequently, the couples at risk of bearing an affected fetus. The diagnostic process is basically divided into two phases: (i) hematologic and hemoglobin data; (ii) molecular analysis of globin genes and, when possible, a genetic study of the family. Since 2003, we have been performing DNA sequence analysis on those cases in which classical molecular methods failed to give a complete diagnostic response, particularly in phenotypes with borderline values of HbA₂ with mild or absent microcytosis. During ten years of screening activities (from 2003 to 2012), twenty-seven unknown or rare nucleotide changes of the β-globin gene have been identified; hematologic and hemoglobin data have been carefully evaluated and, wherever possible, we have conducted a family study to evaluate whether a phenotypic expression could be associated to these nucleotide changes. Because of the limited numbers of cases for each mutation, the significance of these nucleotide substitutions has still not been fully clarified, and this raises a number of questions that need to be answered when carrying out appropriate genetic counseling for couples presumed to be at risk.

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Cardiac disease in thalassemia is determined by the accumulation of iron in the tissue. Genetic factors could influence the severity and the rapidity of the modifications of the cardiac tissue. Mutations or polymorphisms of genes have already been described as being implicated in cardiac disease. In particular, we studied the polymorphisms C1091T in the Connexin 37 gene (CX 37), 4G -668 5G in the Plasminogen Activator Inhibitor-1 gene (PAI 1) and 5A-1171 6A in the Stromelysin-1 gene (SL) in 193 randomly selected patients affected by hemoglobinopathies and 100 normal subjects randomly selected from the general population. A retrospective analysis based on history, clinical data and imaging studies was carried out to assess the presence and type of heart disease. The results of our study do not demonstrate a close association between polymorphism in these candidate genes and cardiac disease, and in particular with myocardial infarction in a cohort of Sicilian patients affected by hemoglobinopathies.

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Nonsense-mediated mRNA decay (NMD) is a surveillance system to prevent the synthesis of non-functional proteins. In β-thalassemia, NMD may have a role in clinical outcome. An example of premature translation stop codons appearing for the first time is the β-globin cd39 mutation; when homozygous, this results in a severe phenotype. The aim of this study was to determine whether the homozygous nonsense cd39 may have a milder phenotype in comparison with IVS1,nt110/cd39 genotype. Genotypes have been identified from a cohort of 568 patients affected by β-thalassemia. These genotypes were compared with those found in 577 affected fetuses detected among 2292 prenatal diagnoses. The nine most common genotypes, each with an incidence rate of 1.5% or over, and together accounting for 80% of genotype frequencies, underwent statistical analysis. Genotype prevalence was calculated within the overall group. Results are expressed as proportions with 95% confidence intervals; p ≤ 0.05 was considered statistically significant. A binomial distribution was assumed for each group; z-tests were used to compare genotype frequencies observed in the patient group with frequencies in the affected fetus group. In the absence of selecting factors, prevalence of these two genotypes was compared between a cohort of 568 β-thalassemia patients (PTS) and 577 affected fetuses (FOET) detected during the same period. IVS1,nt110/cd39 was significantly more prevalent in FOET than PTS (p < 0.0001), while there was no significant difference in prevalence of cd39/cd39 in FOET compared with PTS (p = 0.524). These results suggest a cd39 genotype NMD mechanism may be associated with improved clinical outcomes in thalassemia major. Full article

Several attempts have been made previously to differentiate β-thalassaemia trait (BTT) from other microcytic anaemias using formulae with red cell (RC) parameters. Presently available formulae have low sensitivity and specificity. We wanted to develop a more precise algorithm, which could be used in situations where the gold-standard test for thalassaemia diagnosis: the high performance liquid chromatography (HPLC) is not available. The study was carried out prospectively from November 2008 to March 2010 from randomly collected blood samples with a mean cell volume (MCV) of less than 80 fL. HbA2 measured by HPLC was used to diagnose BTT. We used Fishers stepwise linear discriminant function analysis to develop an algorithm with RC parameters. Calculated new index Thal-index was then subjected to receiver operating characteristic curve analysis to identify best cutoff to discriminate BTT from other microcytic blood films. Software was developed to predict the BTT status (BTT prediction.exe). New index, referred to as the Thal-index, was calculated using discriminant function analysis and is given as Thal-index = [(0.615 x MCV) + (0.518 x mean corpuscular hemoglobin) + (0.446 x red cell distribution width)]. A value of 59 for Thal-index has 90% sensitivity and 85% specificity for differentiating BTT from other microcytic anaemias. This showed better sensitivity and specificity compared to other formulae presently used (i.e., Mentzer in Eshani, et al.). Our study gives a better answer to set-up where HPLC is not available. Although this cannot replace HPLC, BTT prediction.exe is useful to predict instantly and is the first ever computer program available for this function.

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