Screening For Beta-thalassemia Research Articles

Mutation Analysis of Exon 1 in the Hemoglobin Subunit Beta (HBB) Gene in Beta-Thalassemia.

Introduction Thalassemia is a widely prevalent monogenic hematological disorder found worldwide. It exists in two forms: alpha- and beta-thalassemia. Alterations in the hemoglobin subunit beta (HBB) gene cause beta-thalassemia, with missense and point mutations affecting beta-globin synthesis. Consequently, genetic screening for beta-thalassemia is essential for genetic counseling, carrier screening, and prenatal diagnosis. Aim and objective This study aims to examine and identify mutations in the exon 1 region of the HBB gene in beta-thalassemia patients from the Vijayapura region. Methods This study involved 47 clinically diagnosed children with beta-thalassemia from a hospital in Vijayapura, India. Detailed clinical histories of all patients were recorded. Genomic DNA was extracted from the blood samples of these patients and subjected to polymerase chain reaction (PCR) using exon-specific primers for the HBB gene. The PCR products were then sequenced using the capillary-based Sanger sequencing method to identify mutations in the HBB gene. Results A total of 47 clinically diagnosed beta-thalassemia patients were included in the study, comprising 30 males and 17 females, aged between one and 20 years. Sequencing analysis of exon 1 in the beta-globin gene identified 17 beta-thalassemia variants. The most common mutation observed was T>G, G>C, C>A, and C>T in the exon 1 region of the HBB gene. Conclusion This study identifies the pattern of beta-thalassemia mutations, aiding in the prevention of the disorder through prenatal diagnosis and genetic counseling. Mutations can alter codon sequences, affecting protein production. Research highlights the importance of a primary prevention program to analyze mutations and sequence variations at the molecular level, thereby helping to address numerous genetic disorders.

Influence of iron deficiency anemia on hemoglobin A2 Levels: Possible consequences for beta thalassemia screening

Influence of iron deficiency anemia on hemoglobin A2 Levels: Possible consequences for beta thalassemia screening

Feasibility of combining short tandem repeats (STRs) haplotyping with preimplantation genetic diagnosis (PGD) in screening for beta thalassemia.

β-thalassemia is an autosomal recessive disease with the reduction or absence in the production of β-globin chain in the hemoglobin, which is caused by mutations in the Hemoglobin subunit beta (HBB) gene. In Vietnam, the number of β-thalassemia carriers range from 1.5 to 25.0%, depending on ethnic and geographical areas, which is much higher than WHO's data worldwide (1.5%). Hence, preimplantation genetic diagnosis (PGD) plays a crucial role in reducing the rate of β-thalassemia affected patients/carriers. In this research, we report the feasibility and reliability of conducting PGD in combination with the use of short tandem repeat (STR) markers in facilitating the birth of healthy children. Six STRs, which were reported to closely linked with the HBB gene, were used on 15 couples of β-thalassemia carriers. With 231 embryos, 168 blastocysts were formed (formation rate of 72.73%), and 88 were biopsied and examined with STRs haplotyping and pedigree analysis. Thus, the results were verified by Sanger sequencing, as a definitive diagnosis. Consequently, 11 over 15 couples have achieved pregnancy of healthy or at least asymptomatic offspring. Only three couples failed to detect any signs of pregnancy such as increased Human Chorionic Gonadotropin (HCG) level, foetal sac, or heart; and one couple has not reached embryo transfer as they were proposed to continue with HLA-matching to screen for a potential umbilical cord blood donor sibling. Thus, these results have indicated that the combination of PGD with STRs analysis confirmed by Sanger sequencing has demonstrated to be a well-grounded and practical clinical strategy to improve the detection of β-thalassemia in the pregnancies of couples at-risk before embryo transfer, thus reducing β-thalassemia rate in the population.

An efficient isoelectric focusing of microcolumn array chip for screening of adult Beta-Thalassemia

Traditional capillary isoelectric focusing (cIEF), liquid chromatography (LC) and capillary zone electrophoresis (CZE) still suffered from low resolution for hemoglobinopathy screening. Herein, a 30-mm pH 5.2–7.8 microcolumn IEF (mIEF) array chip was developed for hemoglobinopathy screening. As a proof of concept, adult beta-thalassemia was chosen as a model disease. In the method, blood samples were hemolyzed via hemolysin solution and loaded into the microcolumn. The experiments showed that (i) the species of Hb A, F, A2 and variants were clearly separated in the chip, and the resolution was greatly higher than the ones of LC/CZE/cIEF; (ii) up to 24 samples could be simultaneously analyzed in 12-min run; (iii) the intraday and interday RSDs were respectively 3.32–4.91 % and 4.07–5.33 %. The assays of mIEF to total 634 samples were compared with the ones of LC (n = 327) and PCR (n = 307). The cutoff of 3.5 % HbA2 led to the sensitivity of 100 % and specificity of 89.1 % for the mIEF-based screening; and there was 96.7 % coincidence between the methods of mIEF and PCR if refer Hb A2 and F. The method had the merits of facility, efficiency, specificity and sensitivity in contrast to the currently-used methods, implying its potential to screening of beta-thalassemia and hemoglobinopathies.

Healthcare professionals’ perceptions of implementing a decision support intervention for cascade screening for beta-thalassemia in Pakistan

Counselling relatives of individuals with βeta-Thalassaemia Major (β-TM) about cascade screening is the role of field officers (FOs) in the Punjab Thalassaemia Prevention Project (PTPP). This paper presents FOs’ views about using a ‘decision support intervention for relatives’ (DeSIRe) to facilitate informed decision making, and their perception of its implementation and sustainability. Semi-structured qualitative interviews were conducted with nine FOs (June to July 2021) in seven cities in the Punjab province (Lahore, Sheikhupura, Nankana Sahab, Kasur, Gujranwala, Multan, and Faisalabad) following its use in routine clinical practice. Thematic analysis shows that the FOs were overwhelmingly supportive of the DeSIRe, expressing enthusiasm and identifying benefits of its use, both for their own practice and for relatives. They supported the aim of the intervention to enable them to facilitate relatives’ decision-making about cascade screening, and advocated its use more widely within the PTPP and the other provinces of Pakistan. Overall, the DeSIRe was valued by the FOs for use in routine practice. These findings suggest the DeSIRe is highly likely to be implemented by healthcare professionals more widely in the PTPP and, therefore, is worth evaluating to prove its efficacy. Further research is needed on the extent to which the DeSIRe could be adapted for use by other healthcare professionals with similar responsibilities in the other provinces of Pakistan, and in other low-middle income countries.

Indeks Formula Eritrosit Untuk Uji Skrining Talasemia Beta Minor

Erythrocyte indices have been used as the first indicator in screening for beta-thalassemia minor. However, iron deficiency in hemoglobinopathies can reduce the sensitivity of screening, and the spectrum of mutations of different hemoglobinopathies between populations will result in discontinuation of the results of different erythrocyte indices. The research objective in this study was to determine the description of the erythrocyte indices used to screen for beta-thalassemia trait in Ciamis. The research method used in this study was a quantitative descriptive, using a cross-sectional study, data collection had been done during March-May 2021. The subjects of this study were 104 parents of a beta-thalassemia trait who have children with a beta-thalassemia major in Ciamis. The examination parameters used were complete blood count, with processing twenty-six erythrocyte formula index values. Ninety-two respondents were included in the inclusion criteria. The results of the erythrocyte indices in beta-thalassemia trait are England and Fraser, RBC, Mentzer, Srivastava, Shine and Lal, Ricerca, Green and King, Das Gupta, Jayabose, Telmissani-MCHD, Telmissani-MDH, Huber-Herklotz, Kerman I, Kerman II, Sirdah, Ehsani, Keikhaei, Nishad, Wongprachum, Sehgal, Pornprasert, Sirachainan, Bordbar, Matos and Carvalho and CRUISE has cut-off value in that range according to previous studies. Only the Bessman erythrocyte indices has a value of 17, exceeding the cut-off. Twenty-five erythrocyte indices with cut-off value according to previous studies can be used for beta-thalassemia screening in Ciamis, except for the Bessman erythrocyte indices.

Cascade screening for beta-thalassemia in Pakistan: development, feasibility and acceptability of a decision support intervention for relatives

The government-funded ‘Punjab Thalassaemia Prevention Project’ (PTPP) in Pakistan includes cascade screening for biological relatives of children with beta-Thalassaemia Major (β-TM). However, there is low uptake of cascade screening. This paper presents the (i) development of a paper-based ‘decision support intervention for relatives’ (DeSIRe) to enable PTPP Field Officers to facilitate informed decision making about carrier testing, and (ii) assessment of the feasibility and acceptability of the DeSIRe. The intervention was developed using the International Patient Decision Aids Standards quality criteria and Ottawa Decision Support Framework. Twelve focus groups were conducted (September and October 2020) to explore the views of healthcare professionals (HCPs) and relatives of children with β-TM, in six cities. The focus groups were attended by 117 participants (60 HCPs and 57 relatives). Thematic analysis showed that the DeSIRe was considered acceptable for supporting relatives to make informed decisions about cascade screening, and potentially feasible for use in clinical practice. Suggestions for changing some words, the structure and adding information about how carrier testing relates to consanguineous marriages will enable further development of the DeSIRe. Participants generally welcomed the DeSIRe; however, they highlighted the perceived need to use more directive language, hence showed a cultural preference for directive genetic counselling. The findings highlight challenges for researchers using western theories, frameworks, policies and clinical guidelines to develop decision support interventions for implementation more globally. Future research is needed to evaluate the use of the DeSIRe in routine practice and whether it enables relatives to make informed decisions.

The ethics of genetic screening for beta thalassemia in Vietnam.

In this paper, I argue that genetic screening for beta thalassemia major is ethically justified in the context of Vietnam. First, I differentiate genetic screening from the moral objections commonly associated with eugenics on the basis of the primary motive for screening (avoidance of suffering) and the preservation of voluntary choice. To lay the groundwork for ethical discussion, I explain the basics of beta thalassemia biochemistry and screening and the clinical picture of beta thalassemia major. I then elaborate on a specific example of the challenges of beta thalassemia major in Cyprus before moving on to the case of Vietnam and discuss the improbability of treatment for this disorder in Vietnam and therefore, the extensive suffering that it causes the Vietnamese people. This leads to my argument that a beta thalassemia screening in Vietnam would hold up the ethical principle of nonmaleficence and also preserves and enhances reproductive choice. I then propose that Vietnam's successful COVID-19 response can be used as a roadmap for beta thalassemia screening.

Prevention programmes and prenatal diagnosis for beta thalassemia in Pakistan: A narrative review.

Beta thalassemia in Pakistan is a serious health concern with an estimated 5-8% carrier frequency and birth of 5000 major children every year in the country. The treatment of beta thalassemia major patients poses a great economic burden; hence, the ideal approach towards this disease should encompass effective prevention services. At present only one government funded project "Punjab Thalassemia Prevention Programme" existed in Punjab province, and providing free of cost services for beta thalassemia screening and prenatal diagnosis. Complete blood count and haemoglobin electrophoresis remains the preliminary test for screening, while chorionic villi sampling and amplification refractory mutation system method have been most widely used for molecular diagnosis of beta thalassemia. Modern molecular techniques, non-invasive prenatal diagnosis, and pre-implantation diagnosis are in trial phases. In this review we have discussed the available diagnostic facilities and status of prevention programmes for beta thalassemia in Pakistan as well as future perspectives.

Genetic epidemiology of beta-thalassemia in the Maldives: 23years of a beta-thalassemia screening program.

The Maldives is an archipelago of 407,660 people according to population census of 2014, made up of 20 atolls, which has one of the highest prevalence of β-thalassemia worldwide. However, there is a dearth of studies related to β-thalassemia in the Maldives; therefore, in this study, we aimed to investigate the genetic epidemiology of β-thalassemia in Maldives. Blood samples were collected from 110,504 participants (1992-2015). Hemoglobin and RBC indices were measured on automated hematology analyzers. The quantitation of hemoglobin, HbA2, Hb F, and other abnormal Hb variants were assessed by HPLC. Molecular analysis was performed for the most common mutations in Southeast Asia for only 874 individuals either heterozygous or homozygous for these mutations using reverse dot blot hybridization. We screened 110,504 individuals for β-thalassemia between 1992 and 2015, which is~30% of the entire population. The β-thalassemia carrier frequency was estimated to be 16.2%. Molecular diagnosis of 874 β-thalassemia carriers/major was performed for the most common seven mutations in Southeast Asia; of these, 139 patients were diagnosed as β-thalassemia major. This analysis showed that the most common mutations were IVS1+5G>C, (678; 77.6%), followed by the CD 30 (136; 15.6%). The least frequent mutation was FS8/9, (1, 0.001%), followed by IVS1+1G>T and CD15 (2; 0.2%). The frequency of β-thalassemia varies significantly among the 20 different atolls in Maldives. This study is expected to improve genetic counseling, creating awareness, enhance premarital screening, and customize the prevention and treatment strategies based on the needs of each atoll.

Red Cell Indices in Screening of Thalassemia Trait During Antenatal Period.

Baliyan et al. (in J Obstet Gynecol 10.1007/s13224-019-01220-8, 2019) in their study evaluated the sensitivity and specificity of MCV and MCH for the screening of the beta thalassemia trait in late pregnancy. However, they failed to rule out iron deficiency, which is a confounding factor for low MCV and MCH; as a result, they observed low specificity. Authors recommend ruling out iron deficiency prior to screening for beta thalassemia and preferably in the first trimester of pregnancy so that antenatal diagnosis can be performed in high-risk subjects if necessary.

The frequency of iron deficiency anemia and beta thalassemia carriers involunteers of marriage

Introduction: Thalassemia is one of the most important diseases associated with mild microcytic anemia, beta-thalassemia minor. This anemia usually does not require treatment, but it is important to screen for this anemia, especially before marriage, to prevent the birth of a newborn with thalassemia major in parents with β-thalassemia minor. Therefore, the aim of this study was to evaluate the prevalence of thalassemia and iron deficiency anemia in married couples of Ahwaz. Methods: This study is a cross-sectional and descriptive study. 5 cc of blood were prepared in two tubes containing EDTA and Hemoglobin, MCV, MCH, RDW were determined by the System KX21 solenoid and the amount of ferritin, iron, and TIBC was also found in the serum sample. Blood samples from the MCV, MCH low electrophoresis and HbA2 measurements are measured. Results: In this study 16281 couples (32,562) marriage volunteers who were referred to health centers in east and west of Ahwaz were studied. The results showed that the mean of ferritin, MCV and MCH hemoglobin was higher in males than in females. Of the 32,562 people surveyed (5.86%), 1908 had thalassemia minor, of which 966 (5.93%) and 942 (5.79%) were female. In addition, (30.44%), 3041 (10.69%) were 1741 males and (99.7%) were 1,300 women with alpha thalassemia. Of the 32,562 patients (55.1%), 504 had an anemia. Of these, were 284 (74.1%) men and 220 (1.25%) women. Conclusion: The results of this study showed that the prevalence of iron deficiency anemia, thalassemia minor and sickle cell anemia in β-thalassemia carriers were higher among those referring to Ahwaz health center than other cases. On the other hand, in the case of thalassemia continued beta-thalassemia screening of couples in this city can effectively prevent the birth of a newborn with thalassemia major and impose unwanted treatment costs.

Motivational Interviewing and Compliance with Carriers Screening for Beta-Thalassemia Trait in Zahedan Premarital Counseling Center, Iran

Background: Screening and early genetic counseling programs for beta-thalassemia (BT) are of paramount importance during the pre-pregnancy period in high-risk individuals. Objectives: The current study aimed to evaluate the efficacy of motivational interviewing on couples` compliance with carriers screening for BT. Methods: The study was performed on 80 couples with suspected blood indexes for thalassemia trait (mean corpuscular volume (MCV) < 80 and/or mean corpuscular hemoglobin (MCH) < 27 and hemoglobin (Hb) A2 ≤ 3.5), referred to Zahedan premarital counseling center (PCC), Iran, from April 2015 to January 2016. The participants were randomly divided into motivational interviewing (MI) and routine care (control) groups; compliance was considered as number of couples referring to the center after 30 days post-intervention for re-evaluation of blood indexes, and in the second phase, if needed, referring to Zahedan prenatal diagnosis (PND) center for genetic testing, within five months. Results: In the first phase, noncompliance rates were 9.86% and 26.03% for the motivational interviewing (MI) and control groups, respectively. Preventive fraction (PF) indicated a 62% reduction in noncompliance after one month. In the second phase, five months after MI, noncompliance rates were 79.17% and 94.74% in the MI and control groups, respectively (PF=0.17). Conclusions: The MI group showed better compliance with short-term BT screening program, evidenced by higher rates of referral to the PCC.

Carrier screening for beta-thalassemia in the Maldives: perceptions of parents of affected children who did not take part in screening and its consequences.

The Republic of Maldives (Maldives) is an island nation in the Indian Ocean with a population of 344, 023. Studies show that Maldives has one of the world's highest thalassemia carrier rates. It is estimated that 16-18% of the Maldivians are β-thalassemia carriers, and approximately 28 new β-thal cases are recorded annually. Poor uptake of screening for the condition is one of the main reasons for this high number of new cases. The aim of this study was to explore the reasons for not testing for thalassemia in Maldives before or after marriage. Findings show that participants did not undergo carrier tests because of poor awareness and not fully knowing the devastating consequences of the condition. The outcomes of not testing were distressing for most participants. Religion played a vital role in all the decisions made by the participants before and after the birth of a β-thal child.

Effect of antiretroviral therapy on hemoglobin A2 values can have implications in antenatal beta-thalassemia screening programs

Background: Raised hemoglobin-A2 (HbA2) is the diagnostic hallmark of beta-thalassemia trait (βTT). Diagnostic difficulties may arise in HIV-positive patients on antiretroviral therapy (ART). We compared the effect of various antiretroviral drugs on HbA2 levels. We attempted to determine which drugs elevate HbA2 levels causing a false-positive diagnosis of βTT and correlate the findings with red cell indices. Methods: A retrospective analysis of the records of an antenatal thalassemia screening program was carried out for 78 HIV-positive adults (70 antenatal women and 8 husbands) to study the effect of antiretroviral drugs on HbA2 levels. Three had βTT; 20 treatment-naïve subjects constituted controls. The effects of zidovudine (36 cases), stavudine (7 cases), and tenofovir (12 cases) were evaluated. High-performance liquid chromatography was done for HbA2 levels. Values of 3.5–3.9% were borderline and ≥ 4% with hypochromic microcytosis was considered to be βTT. Results: Twenty individuals not on ART had normal HbA2%. Three patients had βTT and showed hypochromic microcytosis despite being on zidovudine. Fourteen of 55 patients on treatment (25.5%) had borderline HbA2 values (mean 3.7%): 11 were on a zidovudine-based regimen and 3 on a stavudine-based regimen. One patient on zidovudine had 4.1% HbA2 with normal Hb and severe macrocytosis (MCV 128.5 fl), leading to a false suspicion of βTT. All patients on tenofovir had normal HbA2. Hematological parameters, including mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH), and HbA2 levels were increased due to antiretroviral drugs zidovudine and stavudine. Conclusion: Treatment-naïve subjects and those on tenofovir showed no effect on HbA2 levels compared with zidovudine and stavudine. A proportion of patients on zidovudine or stavudine had borderline elevated HbA2 levels, which could lead to a false impression of βTT.

Distribution of hemoglobinopathies in patients presenting for electrophoresis and comparison of result with High performance liquid chromatography

Background: Nearly 226 million carriers of thalassemias and abnormal hemoglobin are present worldwide according to the World Health Organization (WHO). The laboratory plays an important role in the investigation of the thalassemias and hemoglobinopathies. Cellulose acetate electrophoresis at alkaline pH and diagnosis based mainly on visual impression of thickness of band may miss the thalassemic trait patients. The aim of this study was to find out different hemoglobinopathies and thalassemia presenting in our hospital and to compare electrophoresis results with HPLC.Materials and Methods: This study was performed in the hematopathology section of Department of Pathology of Tribhuvan University Teaching Hospital on cases sent for electrophoresis during 18 months period from October 2013 to March 2015 and included hemoglobinopathies and thalassemias identified by either electrophoresis or HPLC. 97 cases fulfilled the inclusion criteria and thus were included in the study. Electrophoresis at alkaline pH was done in all whereas HPLC was performed in 27 cases.Results: A sharp peak of hemoglobinopathies and thalassemias was seen in Tharu community though other communities are also affected. Thalassemia trait was the most common diagnosis (26.8%) followed by sickle cell anemia (21.6%). Electrophoresis was efficient in detecting some alpha thalassemia variants but missed many cases of beta thalassemia trait.Conclusion: Beta Thalassemia trait and sickle cell anemia both are common in Nepal , along with some other hemoglobinopathies A sharp peak of hemoglobinopathies and thalassemias are seen in Tharu community. These abnormal hemoglobins and thalassemias are mainly seen in Terai region. Electrophoresis fails to quantify hemoglobin percentage and thus is not appropriate test in beta thalassemia screening.

Prenatal screening and counseling for genetic disorders

Introduction: The carriers of the same autosomal recessive disorder are usually unaware of onset of the genetic diseases in the children even if screenings are available for many of these disorders. In this paper, we report the experience of the Prenatal Diagnosis Center of AOU Federico II and we discuss the role of the screening for beta-thalassemia (BT), cystic fibrosis (CF) and for other rare genetic disorders.Materials and Methods: We analyzed retrospectively the indication for Prenatal Diagnosis (PD) of all the couples referred to our center from January 1993 to May 2013. We divided our sample into three groups: couples at high risk for BT, for CF and for other rare genetic disorders.Results: From January 1993 to May 2013, we performed 1269 PD for genetic disorders. There are still couples who discovered to be carriers of BT by screening after the birth of the affected child (n = 51 (11,3%)); the majority of the people were screened for CF carrier after the birth of an affected child (n = 155 (80,7%)) or through the cascade screening (n = 28 (14,6%)). Large-scale screenings for rare genetic conditions are not available and people were screened only if they have a positive familial history.Conclusion: Parental screening is available for many severe and rare diseases whose genetic origin is known. The proportion of patients referred for very high-risk indications increased over time with an higher demand for rare disease. An adequate counseling is fundamental to identify women at risk for having affected child. Screening, counseling and PD of genetic diseases is a complex matter and needs for a continuous update.

Two decades of pre-marital screening for beta-thalassemia in central Iran

Thalassemia is the most widespread recessive disease worldwide (Ryan et al. 2010; Weatherall and Clegg 2001). Beta-thalassemia is characterized by the deficiency or absence of beta globin production. The condition is clinically mild in the healthy carrier that can be easily detected through routine blood testing, but intermediate or severe in the patients who are born with 25 % chance at each pregnancy from parents who are both healthy carriers. Thalassemia carriers are today present worldwide with high frequencies mainly in the endemic countries of Africa, the Middle East, the Indian subcontinent, Southeast Asia, and the Mediterranean region (Fucharoen and Winichagoon 2007; AlHamdan et al. 2007; Sarper et al. 2009). Thalassemia is a common disease in Iran with higher frequencies in the north and south parts of the country (Haddow 2005; Samavat and Modell 2004; Moafi et al. 2010). Thalassemia major leads to serious medical, social, and economic problems for patients and their families, and patient’s care represents a considerable financial burden for the public health budget (Verma et al. 2011; Langlois et al. 2008). After a 5-year pilot screening, the Iranian Ministry of Health approved in 1996 a mandatory national screening protocol for premarital testing. This program included a laboratory strategy to identify and counsel couples at risk providing support and care (Samavat and Modell 2004; Iranian Health 2004). Although compared to other regions, the Isfahan province can be considered an area at moderate prevalence; premarital screening was locally started in 1992 and gradually extended to the entire province by 1997 (Zeinalian et al. 2009). This report presents the results of the premarital screening program applied in the Isfahan province during the last two decades (1992–2010).

Carrier Screening for β-Thalassemia during Pregnancy in India: A 7-Year Evaluation

Premarital screening for beta-thalassemia is not widely acceptable in India; hence, we evaluated the effectiveness of antenatal screening and counseling over 7 years. 61,935 pregnant women were screened using the single-tube osmotic fragility test during their first antenatal visit. Individuals who were positive were investigated further for diagnosis of beta-thalassemia and other abnormal hemoglobins. Spouses of carrier women were tested whenever available. Couples at risk were given the option of prenatal diagnosis. Only 19% of the women registered at the antenatal clinic in the first trimester of pregnancy, and 14% of the women were positive per the osmotic fragility test; 1020 beta-thalassemia heterozygotes and 213 women with other hemoglobinopathies were identified, majority being in the second and third trimesters. Seven hundred and thirteen (69%) of their husbands could be tested, and 37 couples at risk were identified. Only 15 couples had a prenatal diagnosis done. Four couples with affected fetuses opted for termination of pregnancy. The remaining couples either did not respond after counseling or the pregnancies were advanced for prenatal intervention. This first large study shows that antenatal screening is acceptable in India; however, awareness generation is still a primary requisite to make women register early at antenatal clinics and bring their spouses for screening when required.

New analytical tools and epidemiological data for the identification of HbA 2 borderline subjects in the screening for beta-thalassemia

The increase of HbA 2 is the most important feature in the identification of beta-thalassemia carriers. However, some carriers are difficult to identify, because the level of HbA 2 is not in the typical range. Few data are available concerning the prevalence of such unusual phenotypes, and knowing their expected prevalence could be helpful in detecting systematic drifts in the analytical systems for HbA 2 quantification. In this study we report a retrospective investigation in two centres with high prevalence of beta-thalassemia. The prevalence of borderline subjects was found to be 2.2 and 3.0%, respectively. The genotypes of a subgroup of these subjects were then analyzed and in about 25% of cases a mutation in the globin genes was identified. We conclude that the occurrence of HbA 2 borderline phenotypes is not a rare event. In order to obtain more accurate HbA 2 measurements the development of an international reference measurement system for HbA 2, based on quantitative peptide mapping, has been recently started. We believe that the innovative approach of our method could also be used as a model to develop accurate quantitative methods for other red cell proteins relevant to the biodynamic properties and the surface electrochemistry of erythrocytes.