Prenatal screening for haemoglobin disorders

Prenatal Diagnosis and Screening of Thalassemia Mutations in Bangladesh: Presence of Rare Mutations

Thalassemia is the most common congenital monogenic disorder in Bangladesh. Prenatal diagnosis (PND) and pregnation termination of an affected child is one of the best options to reduce the burden of thalassemic children. This article reports the results of DNA analyses of chorionic villus sampling (CVS) and amniocentesis of fetuses of mothers who came to the thalassemia center of Dhaka Shishu (Children) Hospital, Dhaka, Bangladesh. DNA analysis was done by real-time polymerase chain reaction (qPCR) and Sanger sequencing. Maternal contamination was ruled out by variable number of tandem repeats (VNTRs). A total of 232 samples were analyzed. Hb E (HBB: c.79G>A)/β-thalassemia (Hb E/β-thal) was the most common type of thalassemia seen in 32 samples (13.79%) followed by β-thal major (β-TM) in 10 cases (4.31%). Molecular characterization of the most predominant mutation was IVS-I-5 (G>A) (HBB: c.92+5G>C). The analysis also revealed five rare mutations: IVS-II-654 (C>T) (HBB: c.316-197C>T), IVS-II-1 (G>A) (HBB: c.315+5G>A), codon 44 (-C) (HBB: c.135delC), -86 (C>A) (HBB: c.-136C>A) and codons 14/15 (+G) (HBB: c.45_46insG), which have not been reported previously in Bangladesh. This study provides important information for PND and will help in the development of similar diagnostic programs for other DNA centers in Bangladesh.

Prevalence of Thalassemia Traits and Iron Deficiency Anemia in Sindh, Pakistan

Among microcytic hypochromic anemias, the most common disorders are iron deficiency anemia and co-pathological conditions such as α- or β-thalassemia (α- or β-thal) traits. The aim of the present study was to determine the frequency and prevalence of iron deficiency anemia and α- or β-thal traits based on clinical laboratory data across different ethnic groups in five districts of Sindh Province, Pakistan. The present retrospective study analyzed 3 years (2012-2015) of encoded and unlinked clinical laboratory data, and identified 3030 microcytic hypochromic anemia cases. The data contained complete blood counts (CBCs) with smear morphology examinations, serum ferritin levels, and hemoglobin (Hb) electrophoreses. After reviewing the data, 994 confirmed subjects (iron deficiency anemia and α- and β-thal traits) were then selected for the present study. The prevalence of α- and β-thal traits was highest in Badin district (35.27%), while the prevalence of iron deficiency anemia was highest in Larkana district (30.73%). According to the ethnic-wise distribution, higher numbers of α- and β-thal trait cases were seen in the Sindhi ethnic group [375 (64.21%) and 283 (69.02%), respectively] than in the other ethnic groups. In addition, a higher distribution of β-thal trait cases was observed in the Sindhi ethnic group [n = 327 (56%)] in α- and β-thal cases overall. Findings from the present study strongly suggested that screening is important not only for β-thal trait but also other traits as well. However, careful monitoring of CBC parameters, including red blood cell (RBC) indices and morphology, along with clinical findings are essential to diagnose carrier cases, especially in high prevalence areas.

Iron: effect of overload and deficiency

Iron is a redox active metal which is abundant in the Earth's crust. It has played a key role in the evolution of living systems and as such is an essential element in a wide range of biological phenomena, being critical for the function of an enormous array of enzymes, energy transduction mechanisms, and oxygen carriers. The redox nature of iron renders the metal toxic in excess and consequently all biological organisms carefully control iron levels. In this overview the mechanisms adopted by man to control body iron levels are described.Low body iron levels are related to anemia which can be treated by various forms of iron fortification and supplementation. Elevated iron levels can occur systemically or locally, each giving rise to specific symptoms. Systemic iron overload results from either the hyperabsorption of iron or regular blood transfusion and can be treated by the use of a selection of iron chelating molecules. The symptoms of many forms of neurodegeneration are associated with elevated levels of iron in certain regions of the brain and iron chelation therapy is beginning to find an application in the treatment of such diseases. Iron chelators have also been widely investigated for the treatment of cancer, tuberculosis, and malaria. In these latter studies, selective removal of iron from key enzymes or iron binding proteins is sought. Sufficient selectivity between the invading organism and the host has yet to be established for such chelators to find application in the clinic.Iron chelation for systemic iron overload and iron supplementation therapy for the treatment of various forms of anemia are now established procedures in clinical medicine. Chelation therapy may find an important role in the treatment of various neurodegenerative diseases in the near future.

Establishment of prenatal diagnosis for β-thalassaemia: A step towards its control in a developing country

Beta-thalassaemia constitutes a major health burden on the limited health resources of India and prenatal diagnosis is seen as an important preventive measure to reduce the burden of the disease. Prenatal diagnosis has been offered to 99 women in 112 pregnancies by fetal DNA analysis, using a PCR-based Amplification Refractory Mutation System (ARMS) for the common and uncommon Indian mutations. Restriction fragment length polymorphism (RFLP) for the beta-globin gene was used when the mutation remained unidentified in one of the parents or to complement the ARMS result. In 53 cases the fetus tested had beta-thalassaemia trait (betaTT) (47.3%), 22 were normal (19.6%) and 31 had thalassaemia major (27.6%). In five cases (4.5%), a definitive report could not be given due to maternal contamination. In one case (0.9%), there was a misdiagnosis. Pitfalls encountered in the diagnosis were maternal contamination and occasional non-amplification of the primers. Having established a regional centre for the prenatal diagnosis for thalassaemia, the screening programmes will be enlarged both to identify carriers and prevent the birth of further homozygous children, even during the first pregnancy.

Prenatal diagnosis of beta-thalassemia in Egypt: implementing accurate high-tech methods did not reflect much on the outcome

The clinical severity of thalassemia major makes it a priority genetic disease for prevention programs through prenatal diagnosis for carrier couples. Incorporation of automated DNA sequencing that enables the characterization of mutations not detected by other mutation specific detection procedures was a prime goal of this work. Automated DNA sequencing was offered on fetal tissues in 30 pregnancies during the year 2005. The pregnancies were at high risk for homozygosity or compound heterozygosity for beta-thalassemia based on mutation analysis of both parents before prenatal diagnosis. Both parents have beta-thalassemia trait. Fetal samples were collected by chorionic villus sampling (CVS) in the first trimester and by amniocentesis in the second trimester. The point mutations were characterized by PCR (ARMS). The absence of the expected fragment with all the mutant ARMS primers insinuated an uncharacterized DNA segment that was further subjected to direct automated fluorescent DNA sequencing in an attempt to know if the fetus was affected by parents' mutations. If no mutation was detected using the PCR ARMS, the sample was further analyzed using direct automated fluorescent DNA sequencing. The mean gestation when carrying out the invasive procedure was 14 (10 -18) weeks. All mothers had a previous affected pregnancy, and 13 had two or more previous affected pregnancies. Pregnancies were: 8 carrier fetuses (trait) and 22 affected fetuses in which 2 were homozygous and 20 double heterozygous. Fourteen parents of affected fetuses preferred to continue pregnancy and the babies were born as diagnosed. The other 8 parents decided on termination and DNA of the abortuses proved to be as previously diagnosed by DNA sequencing. The use of PCR amplification and direct sequencing have permitted the accurate characterization of unidentified alleles and successfully solved 100% of the examined samples. However, it has resulted in minor changes of the outcome as the majority of couples preferred continuation of pregnancy.

Study of beta-Thalassemia mutations using the polymerase chain reaction-amplification refractory mutation system and direct DNA sequencing techniques in a group of Egyptian Thalassemia patients

The aim of this study was the molecular characterization of beta-thalassemia (thal) mutations in a group of 95 Egyptian thalassemic patients from Fayoum in Upper Egypt, Cairo, Alexandria and Tanta in Lower Egypt and the Nile Delta. To identify these anomalies, the polymerase chain reaction-amplification refractory mutation system (PCR-ARMS) technique was used, complemented by direct DNA sequencing for uncharacterized cases. In 80 of the 95 patients, the beta-thal mutation was detected by PCR-ARMS. The most common allele encountered in our study was IVS-I-6 (T-->C) (36.3%); the second most common mutation was IVS-I-110 (G-->A) (25.8%). In addition, we report three homozygous cases for the promoter region -87 (C-->G) allele with a frequency of 3.2%. DNA sequencing of uncharacterized cases (14 cases, 15 alleles) revealed six cases (six alleles) of codon 27 (G-->T), and three cases (three alleles) of the IVS-II-848 (C-->A) mutation. Codon 37 (G-->A) in the homozygous state was found in one patient with positive consanguinity. The frameshift codon 5 (-CT) mutation was detected in two of our uncharacterized cases. The codon 15 (TGG-->TGA) mutations was detected in one patient (one allele, 0.5%). All studied cases were fully characterized by this strategy. Screening for beta-thalassemic mutations using ARMS-PCR for the seven most frequent alleles in Egypt succeeded in determining the beta-globin genotype in 84.2% of our patients (91.6% of the expected alleles). To improve the efficiency of routine screening, the PCR-ARMS mutation panel should be updated to include the reported rare alleles. Direct DNA sequencing is an additional way to allow a full characterization of beta-thal patients in the Egyptian population.

Successful Full-Term Twin Pregnancy in Hemoglobin Brockton: A Rare Hemoglobinopathy – Case Report

INTRODUCTION

Hemoglobin Brockton is indicated by the hemolytic anemia, which is rare qualitative variant of aspect of the hemoglobinopathies. Hemoglobin disorders in pregnancy are associated intrauterine growth retardation, premature birth, and low birth weight. One of the unstable hemoglobinopathies, Hb Brockton associated with pregnancy has not been previously mentioned in the literature. In this case presentation and things to be done in case of a pregnant patient with rare hemoglobinopathy have been reviewed in reference to the literature.

CASE REPORT

Twin pregnancy of a 26-year-old patient with Hb Brockton disorder which was diagnosed at the age of 11, and has led to minor hemolytic anemia crisis over the years, was observed. Due to decrease in hemoglobin level, 8 units of transfusion were made. A twin pregnancy continued without any problems until the 38th week when a caesarean section was performed due to breech-breech presentations. The hemoglobin pattern of the newborn was studied at birth and after 1 year; the variant in the mother was not found.

DISCUSSION

During pregnancies with unstable hemoglobinopathy, observation of hemoglobin levels every 3 weeks and carrying out blood transfusions when below 8 g/dl can stabilize the pregnancy in terms of the development of the baby and the mother. Patients with hemoglobinopathy carry an increased risk for complications and should therefore seek medical care early in pregnancy and be managed by a multidisciplinary team of specialists.

Prenatal diagnosis of β-thalassemia in Southern China

OBJECTIVE

To control the birth of thalassemic children in Southern China.

STUDY DESIGN

DNA-based diagnosis was offered on fetal tissues in pregnancies when beta-globin gene mutations were identifiable in both parents using polymerase chain reaction (PCR)-reverse dot blot (RDB) assay. An automated high-performance liquid chromatography (HPLC) system was used to analyze fetal hemoglobin in pregnancies when mutation was unidentified in at least one parent. Fetal samplings were collected by chorionic villi sampling (CVS) in the first trimester, and by amniocentesis or cordocentesis in the second trimester. Maternal contamination of fetal DNA was ruled out by short tandem repeats (STR) analysis.

RESULTS

Five hundered and forty-five fetuses of 540 at-risk pregnancies were performed prenatal diagnosis. Out of 540 fetuses tested by DNA analysis, 150 were found to be normal, 257 were carriers, whereas 133 were affected. Out of five fetuses diagnosed by HPLC, one fetus was affected and four were unaffected. Totally, 133 pregnancies with affected fetuses, except for one twin pregnancy, were voluntarily terminated, leading to a marked reduction of severe beta-thalassemia in this region.

CONCLUSIONS

Our prenatal diagnosis strategy proved to be highly effective. DNA- and HPLC-based testing could enable prenatal diagnosis of beta-thalassemia in all at-risk pregnancies.

Molecular diagnosis of inherited disorders: lessons from hemoglobinopathies

Hemoglobinopathies constitute a major health problem worldwide, with a high carrier frequency, particularly in certain regions where malaria has been endemic. These disorders are characterized by a vast clinical and hematological phenotypic heterogeneity. Over 1,200 different genetic alterations that affect the DNA sequence of the human alpha-like (HBZ, HBA2, HBA1, and HBQ1) and beta-like (HBE1, HBG2, HBG1, HBD, and HBB) globin genes are mainly responsible for the observed clinical heterogeneity. These mutations, together with detailed information about the resulting phenotype, are documented in the globin locus-specific HbVar database. Family studies and comprehensive hematological analyses provide useful insights for accurately diagnosing thalassemia at the DNA level. For this purpose, numerous techniques can provide accurate, rapid, and cost-effective identification of the underlying genetic defect in affected individuals. The aim of this article is to review the diverse methodological and technical platforms available for the molecular diagnosis of inherited disorders, using thalassemia and hemoglobinopathies as a model. This article also attempts to shed light on issues closely related to thalassemia diagnostics, such as prenatal and preimplantation genetic diagnoses and genetic counseling, for better-quality disease management.

Ethnicity and the politics of the new genetics: principles and engagement

Identifying the genetic basis of disease is not a straightforward medical procedure but implicates the broader social, cultural and political context. Ethnicity represents an important part of this context, particularly given the confused and poorly informed debate about genetic differences among supposedly different 'racial' populations. Debates about the 'new genetics', however, have not engaged fully with the issue of ethnicity and racism. This paper, by reviewing a mix of empirical and theoretical debates, explores the discursive practices that inform current thinking on genetics, ethnicity and race. The account begins by exploring some of the philosophical tensions inherent in providing genetic testing. In doing so, the paper argues that current debates about genetics are not neutral but evoke a specific set of received ideas and codes of intervention, embodying social and power relationships. The paper then broadens the discussion by exploring the general meaning of screening and counselling for the 'lay' population, before focusing on the process of providing information and identifying people as carriers. The paper concludes by suggesting that the social space in which the 'new genetics' is enacted, understood and given meaning raises generic concerns, irrespective of ethnicity. These include the potential tension between prevention and informed decision making, whereby ideas about empowering individuals to exercise choice exist alongside a more general societal concern with minimising impairment and illness. In more practical terms, individual choice is compromised by poor-quality care, inadequate information, insensitivity to an individual's worries and concerns and a more general failure to meet his or her needs. At the same time, however, the often racialised perspectives articulated through the activities of service professionals can further complicate the choices and decisions available to minority ethnic populations. The failure to recognise and respond to diversity; blaming minority ethnic populations for their health problems; and the pervasiveness of racist myths and stereotypes in service provision, serve to disadvantage minority ethnic populations. This explains why themes such as equity and access, political engagement as well as more general notions of deservingness based on the construction of citizenship and identity emerge as fundamental in making sense of the relationship between ethnicity and the politics of the 'new genetics'.

Recommendations for introducing genetics services in developing countries

Many concerned scientists believe that developments in the medical application of genomics will widen the gap between the developed and the developing world. We argue that most developing countries now urgently need to incorporate genetic approaches (including DNA diagnosis) into their health services, and that many are able to do so. DNA diagnosis is relatively inexpensive, helps to develop skills in molecular biology and provides a basis for developing national expertise in genomics.

Screening extended families for genetic hemoglobin disorders in Pakistan

BACKGROUND

We have investigated a strategy for identifying and counseling carriers of recessively inherited disorders in developing countries where consanguineous marriage is common. In such communities, gene variants are trapped within extended families, so that an affected child is a marker of a group at high genetic risk.

METHODS

Fifteen large Pakistani families, 10 with a history of a hemoglobin disorder and 5 without any such history (controls), were screened for beta-thalassemia and abnormal hemoglobins. All carriers and married couples consisting of two carriers received counseling, and eight families have been followed for two years.

RESULTS

In the control families, no carrier was found among 397 members tested. In the 10 families with an index case, 183 of 591 persons tested (31 percent) were carriers; carriers had a 25 percent risk of being in a marriage at risk for producing an affected child, and 17 of 214 married couples (8 percent) consisted of two carriers. No couple at risk was identified among 350 randomly selected pregnant women and their partners. All carriers reported that they have used the information provided in the testing and counseling process: carriers married to carriers with two or more healthy children have avoided further pregnancy, and most such couples with one or no healthy children have used prenatal diagnosis. Seven of eight new marriages and engagements are known not to be at risk.

CONCLUSIONS

Testing of extended families is a feasible way of deploying DNA-based genetic screening in communities in which consanguineous marriage is common.

A multi-center study in order to further define the molecular basis of beta-thalassemia in Thailand, Pakistan, Sri Lanka, Mauritius, Syria, and India, and to develop a simple molecular diagnostic strategy by amplification refractory mutation system-polymerase chain reaction

The spectrum of the beta-thalassemia mutations of Thailand, Pakistan, India, Sri Lanka, Mauritius and Syria has been further characterized by a multi-center study of 1,235 transfusion-dependent patients, and the mutations discovered used to assess the fidelity of a simple diagnostic strategy. A total of 44 beta-thalassemia mutations were identified either by allele-specific oligonucleotide hybridization, amplification with allele-specific primers, or DNA sequencing of amplified product. The results confirm and extend earlier findings for Thailand, Pakistan, India, Mauritius and Syria. This is the first detailed report of the spectrum of mutations for Sri Lanka. Two novel mutations were identified, codon 55 (-A) and IVS-I-129 (A-->C), both found in Sri Lankan patients. Two beta-thalassemia mutations were found to coexist in one beta-globin gene: Sri Lankan patients homozygous for the beta0 codon 16 (-C) frameshift were also homozygous for the beta+ codon 10 (C-->A) mutation. Studies of Sri Lankan, Pakistani, and Indian carriers suggest the codon 10 (C-->A) mutation is just a rare polymorphism on an ancestral allele, on which the beta0 codon 16 (-C) mutation has arisen. Each country was found to have only a few common mutations accounting for 70% or more of the beta-thalassemia alleles. A panel of primers to diagnose the majority of the mutations by the amplification refractory mutation system was developed, enabling a simple molecular diagnostic strategy to be introduced for each country participating in the multi-center study.

Attitude of Saudi families affected with hemoglobinopathies towards prenatal screening and abortion and the influence of religious ruling (Fatwa)

Hemoglobinopathies are common inherited disorders in Saudi Arabia. Prenatal diagnosis for such diseases is specific and sensitive but not yet implemented in Saudi Arabia. Saudis are Muslims with a very high rate of consanguinity and inherited genetic disorders. To examine the attitude of Saudi families affected with hemoglobinopathies towards prenatal diagnosis and abortion, and to evaluate the effect of education on religious ruling on such attitudes, 32 families were interviewed using a pre-structured questionnaire. The majority accepted prenatal diagnosis (81.3%). The attitude towards abortion was greatly affected by religious values. Education about religious ruling significantly affected parents' attitude towards accepting abortion and prenatal diagnosis. No other factors were found to influence the outcome. Although the majority of families received some kind of formal genetic counseling [23/32 (71.9%)], none of them was informed about the possibility of prenatal or preimplantation diagnosis prior to the interview. Therefore for prevention of genetic disorders, the emphasis in countries with a vast majority of Muslims such as Saudi Arabia has probably to be placed on public awareness about genetic risks, the risk of consanguinity, availability of services, and so on, while at the same time taking into consideration the religious beliefs and education of the target population

Long-term effect of prospective detection of high genetic risk on couples' reproductive life: data for thalassaemia

Prospective risk detection with availability of prenatal diagnosis is the best service currently available for couples at high genetic risk Here we describe the long term effect of this service on the reproductive life of 102 couples at risk of thalassaemia, whose risk was detected prospectively by carrier screening, who made use of prenatal diagnosis, and where the woman is now over 40. Overall outcome for couples is described in terms of number of favourable versus unfavourable pregnancy outcomes. (A favourable pregnancy outcome = unaffected livebirth, or affected livebirth resulting from informed parental choice.) The 102 couples had a total of 356 pregnancies, including 302 viable pregnancies, and 88% achieved a family unburdened by thalassaemia. 68% of viable pregnancies had a favourable outcome, but only 43% of couples had only favourable outcomes, and 26% lost two or more viable wanted pregnancies. When early losses are included 58% of pregnancies had a favourable outcome, but only 30% of couples had only favourable outcomes, and 41% lost two or more pregnancies. Even with the best available service, at risk couples remain victims of chance, and a significant minority experience great difficulty in obtaining even one healthy child. Research is needed on approaches that may allow couples better control of reproductive outcomes.

Genetic screening in patients of reproductive age. How do you advise prospective parents who want to know specific risks?

At times, determining the actual genetic condition occurring in a family can be very difficult. The most important steps in deciding when testing is appropriate are the patient's age and family history, with special attention to ethnic background. By identifying risk factors before pregnancy, prospective parents can be fully informed about their specific risk of having a child with a genetic condition. Furthermore, the pros and cons of invasive prenatal diagnostic procedures often can be fully discussed well in advance of an actual pregnancy. Clinical geneticists and genetic counselors can provide valuable assistance when difficult questions or problems arise.

Informed choice in genetic screening for thalassaemia during pregnancy: audit from a national confidential inquiry

OBJECTIVE

National audit of informed choice in antenatal screening for thalassaemia.

DESIGN

Audit from the UK Confidential Enquiry into Counselling for Genetic Disorders.

SETTING

Thalassaemia module of the UK Confidential Enquiry into Counselling for Genetic Disorders.

SUBJECTS

138 of 156 couples who had had a pregnancy affected by a major beta thalassaemia from 1990 to 1994.

MAIN OUTCOME MEASURES

How and when genetic risk was identified for each couple, and whether and when prenatal diagnosis was offered.

RESULTS

Risk was detected by screening before or during the first pregnancy in 49% (68/138) of couples and by diagnosis of an affected child in 28% (38/138) of couples. Prenatal diagnosis was offered in 69% (274/400) of pregnancies, ranging from 94% (122/130) for British Cypriots to 54% (80/149) for British Pakistanis and from 90% in the south east of England to 39% in the West Midlands. Uptake of prenatal diagnosis was 80% (216/274), ranging from 98% (117/120) among British Cypriots in either the first or second trimester to 73% (35/48) among British Pakistanis in the first trimester and 39% (11/28) in the second trimester. A demonstrable service failure occurred in 28% (110/400) of pregnancies, including 110 of 126 where prenatal diagnosis was not offered and 48 of 93 that ended with an affected liveborn infant.

CONCLUSION

Although antenatal screening and counselling for haemoglobin disorders are standard practices in the United Kingdom, they are delivered inadequately and inequitably. An explicit national policy is needed, aiming to make prenatal diagnosis in the first trimester available to all couples and including ongoing national audit.

Thalassemia carrier screening and prenatal diagnosis among the British Columbia (Canada) population of Chinese descent

The goal of thalassemia screening is the identification, prior to the conception or birth of an affected child, of couples where both partners are thalassemia carriers. When both partners are identified as carriers for alpha- or beta-thalassemia, the risk of having a fetus who is homozygous or compound heterozygous for the abnormal gene is 25%. A study was performed to identify whether routine screening for thalassemia is indicated for the Chinese population in British Columbia (BC). In a population of 783 subjects, studied either prospectively or retrospectively, 5.0% were alpha-thalassemia carriers and 1.7% were beta-thalassemia carriers. In addition, a review of all BC cases of prenatal diagnosis for thalassemia over a 6-year period indicated that 26% of couples were identified as alpha-thalassemia carriers because of a second or third trimester diagnosis of fetal hydrops, and 17% of couples referred for beta-thalassemia already had an affected child. The experience with prenatal diagnosis shows that a significant proportion of at-risk couples are not identified prior to or early in a pregnancy. The prevalence of carriers for thalassemia would warrant a program of education and routine screening for this condition in the BC Asian population.

Delivering genetic screening to the community

Concern is often expressed that, in the future, screening for genetic risk will become too widespread. Haemoglobin disorders (the thalassaemias and sickle cell disorders) offer an excellent model for genetic screening, because they are common and severe. They are recessively inherited. Carriers can be detected by conventional blood tests with an accuracy of 99%, so couples at risk can be identified before they have children and offered genetic counselling and prenatal diagnosis. Carrier-screening programmes have been in place in several countries for over 20 years and now offer extensive practical experience of the problems of delivering the service equitably to entire populations. This experience suggests that the main risk is of too little rather than too much genetic screening, and of doing it badly, and demonstrates the need for a discipline of 'community genetics'. Here I propose that modern information technology has a central role in providing communities with adequate access to correct genetic information.

Haemoglobinopathies

The inherited haemoglobinopathies are a heterogeneous group of recessive disorders that include the thalassaemias and sickle cell disease. Nearly a thousand mutant alleles have now been characterized. The mutations are regionally specific and in most cases the geographical and ethnic distributions have been determined providing the foundation for a programme of control through screening, genetic counselling and prenatal diagnosis. The main requirements for methodologies providing molecular diagnosis are speed, cost, convenience and the ability to test for multiple mutations simultaneously. For beta-thalassaemia mutations the procedures that meet these requirements are the amplification refractory mutation system and the reverse dot-blot hybridization system. For alpha-thalassaemia the technique of gap PCR is useful for targeting specific deletion mutations but Southern blotting remains the standard diagnostic test.