Iron deficiency anaemia in sickle cell disorders in India

BACKGROUND & OBJECTIVE

Iron deficiency anaemia (IDA) is uncommon in individuals with sickle cell disease (SCD) because of availability of an adequate iron source potentially from increased red cell turnover and from blood transfusions. Also, iron deficiency anaemia can often go unnoticed because the sickle cell disease patients are already anaemic. Iron deficiency in sickle cell patients may result in lowering the intracellular haemoglobin concentration and this may ameliorate sickling. The present study was undertaken to determine the prevalence of iron deficiency anaemia and the response of iron supplementation in sickle cell disorders in tribal population of the four States viz. Maharashtra, Gujarat, Orissa and Tamil Nadu.

METHODS

A total of 8434 individuals (7105 AA, 1267 AS and 62 SS) were tested for zinc protoporphyrin/haem (ZPP/H) ratio and haemoglobin levels. Twenty two sickle cell anaemia (SS), 47 sickle cell trait (AS) and 150 normal control (AA) individuals who were iron deficient, were given iron therapy for a period of 12 wk and the laboratory investigations were repeated at the 13th wk.

RESULTS

Sixty seven per cent of subjects with sickle cell anaemia and 26 per cent with sickle cell trait had elevated ZPP/H ratios (>80 micromol/mol) as against 22.8 per cent of normal individuals. The elevated ZPP/H ratios is an indicator of microcytic anaemia of iron deficiency. Following iron therapy, an improvement in the Hb levels and ZPP/H ratios was observed in both sickle cell disorders and normal individual cases.

INTERPRETATION & CONCLUSION

This study suggests that iron deficiency anaemia is an important problem in Indian sickle cell anaemia patients and iron supplementation should be given only in proven cases of iron deficiency anaemia.

Molecular characterization of G6PD Insuli--a novel 989 CGC --> CAC (330 Arg --> His) mutation in the Indian population

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common red cell enzymopathy among humans. G6PD deficiency was reported in India more than 30 years ago and about 13 biochemically characterized variants have been reported. We now describe the molecular characterization of a distinct biochemical variant from India which was previously characterized by us as a unique Class IV variant with fast electrophoretic mobility. The sequence of the G6PD gene from this variant has revealed the presence of a novel 989 G --> A mutation in exon 9 with a predicted amino acid change of Arg330His.

Clinical examination and hematological data in asymptomatic & apparently healthy school children in a boarding school in a tribal area

In a boarding school of Maharashtra State of India 314 students (Bhil & Pawar) were examined clinically and blood was examined. Anemia was present in 16.2% male & 38.3% female. B (Beta). Thalasemia trait was present in 1.6% male & 2.4% female. Sickle cell trait was present in 21.3% male and 14.4% female and sickle cell disease in 0.6% student. G6PD deficiency was seen in 5.1% male & 4.8% female students.

Genetic Disorders in Haematological Practice in India

Haemoglobinopathies represent a significant national health burden in India. The distribution of specific disorders varies geographically and by community. Heterozygote frequencies of beta-thalassaemia range from 1 to 15%, resulting in an estimated 20 million carriers. HbS is mainly present in tribal and non-caste communities, with carrier prevalences of up to 40%. By comparison, alpha-thalassaemia carriers are found in both the caste and tribal communities, and can reach a frequency of >90% in the latter case. Community control of haemoglobinopathies relies mainly on out-reach education programmes and genetic counselling, with antenatal diagnosis offered in specific major centres. Only partial data are available on the prevalence of haemophilia, but it has been estimated that there are some 50,000 affected individuals nationwide, with an additional 1,500 new cases born each year. RFLP-based techniques have been established to detect mutations in the factor VIII and IX genes, enabling the limited introduction of carrier detection and antenatal diagnosis.

Red cell genetic abnormalities, beta-globin gene haplotypes, and APOB polymorphism in the Great Andamanese, a primitive Negrito tribe of Andaman and Nicobar Islands, India

The Great Andamanese are a primitive Negrito tribe of the Andaman and Nicobar Islands, India, with a total population of 37. We studied 29 individuals from eight families from this population for abnormal hemoglobins, G6PD deficiency, DNA haplotypes, and apolipoprotein B (APOB, gene) polymorphism. Hb E was detected in five individuals, the prevalence of Hb E heterozygotes being 14.3%. One individual had beta-thalassemia trait. One female was G6PD deficient and showed the G6PD Orissa mutation. Haplotype analysis of the beta-globin gene cluster showed that the betaE chromosomes were linked to two haplotypes (- - - - - + + and + + - + + + +) representing the framework 1 gene, whereas the betaA chromosomes showed eight different haplotypic patterns corresponding to framework 1 and 3 genes. APOB polymorphism analysis showed that the 631-base-pair (bp) allele was the predominant one with a high homozygosity rate, which could be due to the higher rate of inbreeding in this isolated group. The presence of Hb E and our findings on haplotype analysis supports the hypothesis that the Great Andamanese are reasonably believed to be the surviving representatives of the Negrito race that once flourished in the entire Southeast Asian region in ancient times.

Detection of the beta s gene: an evaluation of the solubility test against automated chromatography and haemoglobin electrophoresis

The solubility test is evaluated against automated high-performance liquid chromatography (HPLC) and haemoglobin (Hb) electrophoresis for its efficacy in screening for the beta s gene in population groups in remote areas. Blood samples taken from 3246 individuals from the tribal populations of the Dhule and Gadchiroli districts of Maharashtra state were analysed by all three methods. The solubility test detected 871 out of 932 individuals positive for the beta s gene by HPLC and Hb electrophoresis, and showed an overall sensitivity of 93.8% and specificity of 100%, with a positive predictive value of 100% and negative predictive value of 97.4%. Both HPLC and Hb electrophoresis are relatively expensive and not available in most laboratories in remote tribal areas, where the frequency of the beta s gene is very high. We conclude that the solubility test could be used for preliminary screening to determine the prevalence of the beta s gene in different population groups, particularly in remote areas where other facilities are not available. Individuals who test positive for the beta s gene by the solubility test require further investigation by either HPLC or Hb electrophoresis.

Splenomegaly in school children in a remote tribal area of Dhole district, Maharashtra

Sickle-cell gene is known to protect against P. falciparum infection and provides a selective survival advantage in those areas where P. falciparum infection is endemic. This protection is not absolute and many other factors, inherited and acquired also contribute to the immunity against P. falciparum infection. We investigated incidence of splenomegaly and typical history of malaria in the past two years in apparently healthy school children in a tribal area in Dhole district of Maharashtra to see whether the incidence of malaria (splenomegaly and typical history) was different in children having sickle-cell trait to that of those who did not have this trait. A total of 480 school children were clinically examined for splenomegaly and history of typical malaria fever and/or blood slide positivity for malaria in the past two years. About 9.55 per cent of normal population had either splenomegaly or convincing history of malarial infection in the past two years which is not statistically different from the sickle-cell trait patients having evidence of past malaria (8.79 per cent; p > 0.05).

Trimodal distribution of HbS levels in sickle heterozygotes--an useful predictor of the alpha-genotype for population screening

The trimodal distribution of HbS levels in sickle heterozygotes has been used as an indirect approach to determine the prevalence of alpha-thalassaemia in different population groups. We used this approach to predict the alpha-genotypes of 124 sickle cell heterozygotes where the HbS concentration varied from 20 to 46 per cent with antimodes at 28.0 and 33.0. The alpha-genotypes in these individuals were also determined by Southern blot hybridization. We predicted homozygous (-alpha/-alpha) or heterozygous (-alpha/alpha alpha) alpha-thalassaemia-2 in 78 subjects by the trimodal distribution of HbS. However, actual genotyping showed that 75 patients had alpha-thalassaemia. Forty six of the 47 subjects with a normal alpha-globin genotype (alpha alpha/alpha alpha) could be predicted indirectly. The overall sensitivity was 100 per cent and specificity was 94.2 per cent with a positive predictive value of 96.2 per cent and negative predictive value of 100 per cent. As alpha-genotyping is very expensive and not feasible in most laboratories in India, we conclude that the trimodal distribution of HbS levels is a suitable method for screening for alpha-thalassaemia in population studies.

The influence of alpha-thalassaemia on the haematological & clinical expression of sickle cell disease in western India

We evaluated the clinical and haematological features of 29 sickle cell anaemia patients with associated alpha-thalassaemia and 22 sickle cell homozygotes with a normal alpha-globin genotype from western India. The presence of alpha-thalassaemia resulted in significantly higher haemoglobin (Hb), haematocrit (HCT), red blood cells counts (RBC) and haemoglobin A2 (HbA2) levels but lower mean cell haemoglobin (MCH) and mean cell volume (MCV). The clinical presentation in these patients was also milder with fewer episodes of painful crisis, chest syndromes, infections, requirement of hospitalization and blood transfusions. However, splenomegaly was more common as compared to the patients with a normal alpha-globin genotype. It is evident from the present study that alpha-thalassaemia could be an important genetic factor modulating the clinical expression and haematological severity of sickle cell anaemia in this region.

Effect of alpha-thalassemia on sickle-cell anemia linked to the Arab-Indian haplotype in India

Two population groups from Western India with a high prevalence of the beta(S) gene, one tribal (Valsad) and the other nontribal (Nagpur), were studied. The beta(S) gene frequency in both populations was similar (0.22 vs. 0.23), but not the clinical expression of sickle-cell anemia (SS): the sickle homozygotes in the tribal group appeared to have a mild clinical course, whereas the majority in the nontribal group exhibited a more severe clinical phenotype. Both tribal and nontribal SS patients had a similarly high mean hemoglobin (Hb)F expression (18.5% vs. 15.5%) and a high number of F cells (72.3% vs. 66.6%). DNA analysis of the beta-globin gene cluster region revealed that in these two populations, this portion of DNA was identical with and corresponded to the typical Arab-Indian haplotype. Nevertheless, in heterozygotes, the mean beta(S) expression was lower (27.9%) in the tribal as compared to the nontribal group (35.5%). The major epistatic factor distinguishing the milder presentation in tribals vs. a more severe manifestation in nontribals was the very high frequency (0.97) of the alpha-thalassemia gene in the former as compared to the latter (0.24). We conclude that the phenotypic expression of sickle-cell anemia, linked to the Arab-India haplotype and expressing similar levels of HbF and F cells, is not uniformly mild in India and that alpha-thalassemia is a powerful and additional epistatic factor in the Indian subcontinent.

Characterization of G6PD Rohini--a new class III Indian variant

A new Indian G6PD variant was detected in a 15 yr old Maratha male during a population screening programme in high school children in Bombay (India). The propositus and two family members having the same variant were apparently healthy. This enzyme variant has a mild erythrocyte G6PD deficiency and a slow electrophoretic mobility. It is characterized by a high Michaelis-Menton constant for G6P, a bimodal curve for pH optima and a slight decrease in the thermostability. The rate of utilization of substrate analogue is similar to that of normal. These observations suggest identification of a new class III variant, designated as G6PD Rohini.