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

The Changing Trends in Prenatal Diagnosis of Hemoglobinopathies in India: The Quest of a Single Center to Reduce the Burden of Disease over Three Decades

The β-thalassemias and sickle cell disorders pose a considerable health burden in India. Of the more than 10,000 annual births of children with a severe hemoglobinopathy, only around 10.0% are managed optimally. Thus, genetic counseling and prenatal diagnosis (PND) is a valid option for a large and diverse country. Our center was one of the first to initiate PND and we present our experience over 30 years to evaluate the impact of awareness in changing the trends of PND of hemoglobinopathies. Both second and first-trimester diagnoses were undertaken by fetoscopy/cordocentesis and globin biosynthesis/high-performance liquid chromatography (HPLC) analysis of fetal blood and chorionic villus sampling (CVS) and DNA analysis. Over 30 years, 3478 couples (first trimester: 2475; second trimester: 1003) from all over India were offered PND. The number of couples coming in the first trimester increased significantly over each decade and couples coming prospectively increased from 2.5 to 18.4%. A cost-effective stepwise approach was used for molecular analysis. Eight hundred and one fetuses (23.0%) were affected and all except three couples opted for termination of these pregnancies. Genetic counseling and PND is the only way to reduce the burden of disease. With awareness, there was a shift from second trimester to first trimester PND over each decade, with an increasing number of couples coming during the first pregnancy. There are only 15 to 20 centers in India offering PND. We have compared our study with other reports on PND from different regions in India.

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.

Impact of iron deficiency on hemoglobin A2% in obligate β-thalassemia heterozygotes

INTRODUCTION

The potential impact of concomitant iron deficiency on hemoglobin A2 (HbA2)-based identification of β-thalassemia trait (βTT) is a worrisome issue for screening laboratories. This is especially true for resource-constrained settings where iron deficiency is widespread and molecular confirmatory tests for borderline low HbA2 values may be unavailable.

METHODS

Obligate βTT carrier individuals (n = 752) were identified during screening studies on the parents of thalassemia major patients. HbA2%, complete blood counts and serum iron, ferritin and transferrin saturation were studied. Iron-deficient individuals (n = 135) with normal range HbA2% were taken as controls.

RESULTS

Concomitant iron deficiency (defined as ferritin ≤15 ng/mL and/or transferrin saturation ≤15%) was present in 20.7% (156/752) βTT cases, that is, 33.3% females (122/366) and 8.8% males with βTT (34/386). Mean HbA2 in iron-replete βTT was 5.4 ± 0.8 (range 3.1-7.9) and in iron-deficient βTT was 5.4 ± 0.9 (range 3.3-7.6). HbA2 < 4.0% was found in 23/752 (3.1%) βTT: 13/595 iron-replete (2.2%) and 10/157 (6.4%) iron-deficient βTT individuals. However, five of the 10 iron-deficient βTT cases carried the silent CAP+1 (A>C) β-thalassemia allele accounting for the borderline HbA2%. On a separate analysis, all five severely anemic βTT (Hb < 80 g/L) and 16/17 βTT with severe hypoferritinemia (<5 ng/mL) had HbA2 > 4.5%. The single case with serum ferritin 4.8 ng/mL and HbA2 3.3% showed a CAP+1 (A>C) mutation.

CONCLUSIONS

Iron deficiency was prevalent among north Indian βTT individuals, especially women. After adjusting for other causes of low HbA2 in βTT, iron deficiency, even when very severe, was very unlikely to interfere significantly with HbA2-based identification of βTT.

Frequency of β-thalassemia trait and other hemoglobinopathies in northern and western India

INTRODUCTION

India is an ethnically diverse country with an approximate population of 1.2 billion. The frequency of beta-thalassemia trait (βTT) has variously been reported from <1% to 17% and an average of 3.3%. Most of these studies have been carried out on small population groups and some have been based on hospital-based patients. There is also a variation in the prevalence of hemoglobinopathies in different regions and population groups in the country. A high frequency of Hb D has been reported from the North in the Punjabi population, Hb E in the eastern region of India and Hb S is mainly reported from populations of tribal origin from different parts of the country.

OBJECTIVES

To study the gene frequency of βTT and other hemoglobinopathies in three regions East (Kolkata), West (Mumbai) and North (Delhi) in larghe population group (schoolchildren) for a more accurate assessment of gene frequency for planning of control programmes for haemoglobinopathies.

MATERIALS AND METHODS

This study included 5408 children from 11 schools in Delhi, 5682 from 75 schools in Mumbai and 957 schoolchildren from Kolkata who were screened for βTT and haemoglobinopathies. These included 5684 children from 75 schools in Mumbai and 5408 children from 11 schools in Delhi. Children were 11-18 years of age of both sexes. The final report is, however, only on 11090 schoolchildren from Mumbai and Delhi as data from Kolkata was restricted both in numbers and objectives and could not be included for comparison.

RESULTS

The overall gene frequency of βTT in Mumbai and Delhi was 4.05% being 2.68% and 5.47% in children of the two cities respectively. In Mumbai, the gene frequency was evenly distributed. Majority of the children with βTT from Mumbai were from Marathi (38.9%) and Gujarati (25%) speaking groups. Gene frequency was >5% in Bhatias, Khatris, Lohanas and Schedule Castes. In Delhi, a higher incidence was observed in schoolchildren of North and West Delhi (5.8-9.2%). The schoolchildren of North and West Delhi comprised predominantly of Punjabi origin compared to children in the South of the city (2.2%, 2.3%). When analyzed state-wise, the highest incidence was observed in children of Punjabi origin (7.6%) and was >4% from several other states. Majority of the traits from Mumbai were anemic (95.1% male and 85.6% in female). The prevalence of anemia was lower (62.7% male and 58.4% female) children with βTT from Delhi. This was a reflection of the higher prevalence of anemia in children without hemoglobinopathy in Mumbai than in Delhi. Nutritional deficiency was probably more severe and rampant in children Mumbai. Gene frequency of Hb D was greater in schoolchildren from Delhi (1.1%) than in Mumbai (0.7%). Hb S trait (0.2%) was observed exclusively in children from Mumbai. A low incidence of Hb E trait (0.04%) was seen in children in Mumbai. A higher incidence is reported from the East. The number of cases studied from the eastern region was small as the data from the East (Kolkata) could not be included in the analysis.

CONCLUSION

This study comprises a larger number of children studied for the gene frequency of βTT and other hemoglobinopathies from India. Population groups with higher gene frequencies require screening programmes and facilities for antenatal diagnosis as well as increased awareness and educational programmes to control the birth of thalassemic homozygotes. The overall carrier frequency of βTT was 4.05% and reinforces the differential frequency of β-thalassemia trait in schoolchildren from Delhi and Mumbai and the higher incidence of hemoglobin D in Punjabis as reported previously. The birth incidence calculated thereof for homozygous thalassemics would be 11,316 per year which are added each year to the existing load of homozygous thalassemics. This is much higher than the previously reported number of births annually. Hence suitable control measures need to be undertaken urgently in India.

The clinical significance of the spectrum of interactions of CAP+1 (A→C), a silent β-globin gene mutation, with other β-thalassemia mutations and globin gene modifiers in north Indians

OBJECTIVES

To assess the clinical significance of the interactions of CAP+1 (A-->C), a silent beta-globin gene mutation, with other beta-thalassemia mutations and globin gene modifiers in north Indians.

METHODS

The clinical phenotypes associated with compound heterozygosity for the CAP+1 (A-->C) mutation with other beta-thalassemia mutations, together with the potential effect of the genetic modifiers alpha-thalassemia and the Xmn-1(G)gamma C-->T polymorphism were studied in 30 patients. The frequency of the CAP+1 (A-->C) polymorphism was determined and an analysis of the red cell indices, HbA(2) levels, iron status, and alpha-globin genes was carried out in 35 heterozygotes.

RESULTS

Based on an analysis of 1075 beta-thalassemia alleles the CAP+1 (A-->C) mutation constituted 3.2% of north Indians. There was a wide spectrum of phenotypic severity in compound heterozygotes; 18 of 30 were transfusion dependent. There was a very high frequency of the -/- genotype of the Xmn-1(G)gamma polymorphism in compound heterozygotes. Analysis of 35 heterozygotes indicated that approximately half were hematologically normal and therefore genuine 'silent' carriers.

CONCLUSIONS

Compound heterozygotes for CAP+1 (A-->C) and other severe beta-thalassemia alleles are phenotypically severe enough to necessitate appropriate therapy and counseling. The unexpected severity of these interactions may be due, in part, to the high frequency of beta-thalassemia alleles associated with the Xmn-1(G)gamma- allele in Indian populations. It is concluded that the CAP+1 (A-->C) mutation can pose serious difficulties in screening and counseling programs in populations in which it occurs at a significant frequency.