Thalassemia and Hemoglobin Disorders In Khuzestan Province of IranCorrespondence Address :
Fakher Rahim, Physiology Research Center, Ahwaz Jondishapur University of Medical Sciences, Ahwaz, Iran. email@example.comE-Mail:Tel: +986113362411
Background and Aim:In prevalent regions, the thalassaemias often coexist with a variety of structural Hb variants giving rise to complex genotypes and an extremely wide spectrum of clinical and haematological phenotypes. Haematological and biochemical investigations, and family studies provide essential clues to the different interactions and are fundamental to DNA diagnostics of the Hb disorders.
Material and Methods:A careful three tier approach involving: (1) Full blood count (2) Special haematological tests, followed by (3) DNA mutation analysis, provides the most effective way in which primary gene mutations as well as gene-gene interactions that can influence the overall phenotype can be detected. In Iran, there are many different forms of α and β thalassemias. Increasingly, different Hb Variants are being detected, and their effects per se, or in combination with the thalassaemias, provide additional diagnostic challenges.
Result: We did step-by-step diagnostic workup in 800 patients of hemoglobinopathies who were referred to Research center of Thalassemia and Hemoglobinopathies in Shafa Hospital of Ahwaz Joundishapour University of Medical Sciences, respectively. We detected 173 patients as Iron Deficiency Anemia and 627 individuals as Thalassemic patients by use of different indices. We detected 75 %( 472/627) of the β-thalassemia mutations by using amplification refractory mutation system (ARMS) technique and 19 %( 130/627) of the α-thalassemia mutations by using Gap-PCR technique and 6 %( 25/627) as Hb variants by Hb electrophoresis technique successfully.
Conclusion:Almost all haemoglobinopathies can be detected with the current PCR-based assays with the exception of a few rare deletions. The knowledge of α and ÃŸ-gene numbers in α and ÃŸ-thalassemia traits of any population is necessary, as it modifies the phenotype of thalassemia by altering the ratio of α and ÃŸ -chains of hemoglobin.
α and β- thalassemia, Hemoglobin variants, Iron Deficiency Anemia (IDA), Gap-Polymerase Chain reaction (Gap-PCR).
Hemoglobinopathies are inherited disorders of globin, which is the protein component of hemoglobin (Hb). Hemoglobinopathies are the commonest genetic defect worldwide with an estimated 269 million carriers (1). Iran, a country 1,648,000 km2 wide, like many other countries in the region, has a large number of thalassemia patients (2). Thalassemias are the commonest monogenic diseases worldwide. Mutations in genes coding for the globin proteins that alter protein output produce the thalassemia syndromes. Mutations in the globin genes that lead to abnormal proteins are called variant Hbs (3). More than 23 different molecular defects have been identified for α -thalassemia till date. In the case of ÃŸ-thalassemia, presence of over 150 various known mutations, is even more perplexing (4). Thalassemia is found in some 60 countries with the highest prevalence in the Mediterranean region, parts of North and West Africa, the Middle East, the Indian subcontinent, Southern Far East and Southeastern Asia, together composing the so-called thalassemia belt. In western countries, thalassemia affects mostly individuals, whose ancestries are traceable to high prevalence areas [5-8]. Each population-at-risk, however, has its own spectrum of common mutations, usually from five to ten; a finding that simplifies mutation analysis, and thus, determines the origin of the mutant genes. For the purpose of this study, we studied the mutation of the important globin genes in humans i.e the 2 β globin genes and the 4 α globin genes.
Sample collection: Blood samples of 2mL each were collected in EDTA vials and in plain vials from 800 patients (4ml per patient) referred to Research Center of Thalassemia and Hemoglobinopathies (RCTH) ,which is the only center working on hematology and oncology in Southwest (Khuzestan) region of Iran. Time period of the study was Feb 2005 to August 2007.
Full Blood Count: In all these patients, serum ferritin levels (and if necessary serum iron, iron binding capacity and percentage saturation) were sought. This is recommended because at times, particularly during pregnancy, it is possible that iron stores will be low or, in the presence of iron deficiency, it is possible that the MCV or MCH are influenced by the iron deficiency. It is also occasionally seen that the HbA2 level can be falsely lowered by iron deficiency. We attempted to differentiate βâ€“thalassemia from Iron Deficiency Anemia by the help of discriminate indices include Mentzer Index (9), England and Fraser Index (10), Srivastava Index (11), Green and King Index (12), Shine and Lal Index (13), red blood cell (RBC) count, red blood cell distribution width index (RDWI) (14), Mean Density of Hemoglobin per Liter of blood (MDHL) and Mean Cell Hemoglobin Density (MCHD) (15). If iron deficiency is present, it is essential to correct this, and then repeat the full blood count and all other investigations. . We detected 173 patients as IDA and the rest as thalassemia disorders.
Special Haematological Tests: We screened all patients by above mentioned tests and compared all data in order to classify them. It is appropriate to order all tests simultaneously since they take time to do, and often information can be obtained from the tests that might not have been seen to be relevant, when first starting off the investigation of a haemoglobinopathy. Some of the tests are technically demanding and so the person ordering the tests should have some knowledge of the laboratoryâ€™s technical skills as well as experience in interpreting results. Other special haematological tests performed, particularly when investigating the more uncommon variant Hbs were tests for oxygen affinity, haemoglobin stability and detection of methaemoglobin. Mass spectrometry has been used to characterise various variant Hbs (17). The latter approach might be very valuable for population screening, but not for detection involving individual cases, DNA based approaches remain the methods of choice. We compared values of HbA, HbA2, HbF, and Hb variants to confirm our finding, respectively. We found that all of the 627 patients (130 patients suspected to α-thalassemia and 472 patients suspected to β-thalassemia) were having thalassemia. Also we detected 23 individuals who have HbS, HbDpanjub, and two cases were suspected to Hb Lepore (Table/Fig 1). Later on the entire β-globin gene was sequenced using direct mutation analysis by nucleotide base sequencing to confirm Hb Lepore status. Finally we have found that for both cases the presences of Hb Lepore were ruled out. We also compared values of HbA, HbA2, HbF, and Hb variants to confirm our finding, respectively.
Sources of DNA and DNA preparation: The main source of DNA is peripheral leucocytes obtained from peripheral blood anticoagulated, preferably with ethlenediaminetetraacetic acid (EDTA). Fetal DNA is mainly isolated from chorionic villi obtained through ultrasound-guided transcervical aspiration or ultrasound-guided transabdominal aspiration. Foetal DNA can also be prepared from amniotic fluid cells directly or after culture. It is prudent to set aside a few milliliters for cultur
We did step-by-step diagnosis workup in 800 patients with hemoglobinopathies who were referred to Research center of Thalassemia and Hemoglobinopathies in Shafa Hospital of Ahwaz Joundishapour University of medical sciences, respectively. We detected 173 patients as IDA and the rest as hemoglobinopathies by the help of above techniques. Also we found that all of the 627 patients (130 patients suspected to α-thalassemia and 472 patients suspected to β-thalassemia) were having thalassemia. Among the rest 25 cases, we detected 23 individuals ,who had HbS, HbDpunjab, and rest two cases were suspected having Hb Lepore (Table/Fig 1). Later on the entire β-globin gene was sequenced using direct mutation analysis by nucleotide base sequencing to confirm Hb Lepore status. Finally we have found that the presence of Hb Lepore for both cases was ruled out. The most predominant β-thalassemia mutation that we had found was IVS II â€“ 1(G→C) (20 %) followed by another many less frequent known mutations for Southern part of Iran listed in (Table/Fig 2). There were 130 patients who were suspected to have α-thalassemia based on hematological tests in our study. So for confirming that we analyzed the α-globin gene deletion by Gap-PCR technique and found 6 types of mutations in 98 individuals out of 130. The most predominant one was â€“ α 3.7 (62 %) followed by - - MED, â€“ α 5NT, - - MEDII, â€“ α4.2, â€“ α PA , and - - MED /â€“ α 3.7 (HbH) for Southern part of Iran listed in (Table/Fig 3). We detected 6 individuals with three of them were shown values less than 1.0 and by further investigation using molecular analysis techniques confirmed them as β â€“ thalassemia affected cases with heterozygous patterns. Three out of six cases were shown values more than 1.0 and were considered as α-thalassemia cases which by the help of further investigation using molecular analysis techniques were confirmed as α â€“ thalassemia affected cases with heterozygous patterns (Table/Fig 4).
Among all the hemoglobinopathies, Alpha and Beta thalassemias are the commonest. Almost all hemoglobinopathies can be detected with the current PCR-based assays with the exception of a few rare deletions. The complex mutational spectrum of the hemoglobinopathies, especially relevant in a multi-ethnic community, requires a method with the capacity to scan the β (and/or α) globin genes rapidly and accurately for all mutations. The commonest type of β â€“thalasemia seen in Iran is â€“ α 3.7 deletion. Hadavi et al(22) has reported the prevalence of â€“α3.7deletion in the population of Iran as 30.2%.Our data showed the prevalence of- αâ€“3.7 deletion in 20% in the population of Southwest (Khuzestan) region in Iran. In our study we found only two cases of â€“ α4.2 deletion and few cases of any other deletions reported so far. Hadavi et al., (22) have reported â€“ α 4.2 deletion in Iranian subjects with a prevalence of 3.5%. Najmabadi et al., (23),(24) has reported the prevalence of IVS-II-I (G â€”> A) β-thalassemia mutation of 34 % in the population of Southwest region of Iran. In our study, we found that most frequent mutations were CD 36/37, IVS II-I, and IVS I-110 followed by other cases of any other mutations reported so far. Our study showed that most frequent mutations were the single-gene deletion (â€“ α 3.7) in Iranian subjects which is also coherent with other studies. The knowledge of α and ÃŸ-gene number in α and ÃŸ-thalassemia traits in any population is necessary, as it modifies the phenotype of thalassemia by altering the ratio of α and ÃŸ -chains of hemoglobin.
The compactness of the globin genes means that haemoglobinopathy detection is largely a PCR-based approach that can utilize direct sequencing analysis. Almost all haemoglobinopathies can be detected with the current PCR-based assays with the exception of a few rare deletions. However, the molecular diagnostic service is still under development to try and meet the demands of the population it serves. A higher throughput approach will be required to meet practice pressures and the increasing needs set by the antenatal screening programme. This increasing workload dictates increasing automation, which may necessitate the use of automated robotic platforms to prepare samples and reactions, and the use of automated platforms to perform the actual detection. In most populations the β-thalassaemias (and related haemoglobinopathies) are clinically more relevant than the α-thalassaemias. The complex mutational spectrum of the haemoglobinopathies, especially relevant in a multi-ethnic community, requires a method with the capacity to scan the β (and/or α) globin genes rapidly and accurately for all mutations. This aspect is being addressed by the development of arrays. Although in their infancy, the arrays hold great promise and are amenable to scaling up and automation. In the short term, the current generation of instruments such as the capillary electrophoresis systems, has greatly simplified DNA sequence analysis. The capillary electrophoresis system also lends itself to the multiplexed mini-sequencing methodology which is highly suitable for screening for the common globin gene mutations.
This work was supported by the director of Shafa hospital and department of hematology and oncology. The author also wants to thank the patients and their families.
JCDR research services were used in redrafting of the manuscript.
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