Survival and complications in patients with haemoglobin E thalassaemia in Sri Lanka: a prospective, longitudinal cohort study.

BACKGROUND: Worldwide, haemoglobin E ß-thalassaemia is the most common genotype of severe ß-thalassaemia. The paucity of long-term data for this form of thalassaemia makes evidence-based management challenging. We did a long-term observational study to define factors associated with survival and complications in patients with haemoglobin E thalassaemia. METHODS: In this prospective, longitudinal cohort study, we included all patients with haemoglobin E thalassaemia who attended the National Thalassaemia Centre in Kurunegala, Sri Lanka, between Jan 1, 1997, and Dec 31, 2001. Patients were assessed up to three times a year. Approaches to blood transfusions, splenectomy, and chelation therapy shifted during this period. Survival rates between groups were evaluated using Kaplan-Meier survival function estimate curves and Cox proportional hazards models were used to identify risk factors for mortality. FINDINGS: 109 patients (54 [50%] male; 55 [50%] female) were recruited and followed up for a median of 18 years (IQR 14-20). Median age at recruitment was 13 years (range 8-21). 32 (29%) patients died during follow-up. Median survival in all patients was 49 years (95% CI 45-not reached). Median survival was worse among male patients (hazard ratio [HR] 2·51, 95% CI 1·16-5·43), patients with a history of serious infections (adjusted HR 8·49, 2·90-24·84), and those with higher estimated body iron burdens as estimated by serum ferritin concentration (adjusted HR 1·03, 1·01-1·06 per 100 units). Splenectomy, while not associated with statistically significant increases in the risks of death or serious infections, ultimately did not eliminate a requirement for scheduled transfusions in 42 (58%) of 73 patients. Haemoglobin concentration less than or equal to 4·5 g/dL (vs concentration >4·5 g/dL), serum ferritin concentration more than 1300 µg/L (vs concentration ≤1300 µg/L), and liver iron concentration more than 5 mg/g dry weight of liver (vs concentration ≤5 mg/g) were associated with poorer survival. INTERPRETATION: Patients with haemoglobin E thalassaemia often had complications and shortened survival compared with that reported in high-resource countries for thalassaemia major and for thalassaemia intermedia not involving an allele for haemoglobin E. Approaches to management in this disorder remain uncertain and prospective studies should evaluate if altered transfusion regimens, with improved control of body iron, can improve survival. FUNDING: Wellcome Trust, Medical Research Council, US March of Dimes, Anthony Cerami and Ann Dunne Foundation for World Health, and Hemoglobal.

A novel molecular basis for beta thalassemia intermedia poses new questions about its pathophysiology.

During a study of the molecular basis for severe forms of beta thalassemia in Sri Lanka, 2 patients were found to be heterozygous for beta thalassemia mutations. Further analysis revealed that one of them has a previously unreported molecular basis for severe thalassemia intermedia, homozygosity for quadruplicated alpha globin genes in combination with heterozygous beta thalassemia. The other is homozygous for a triplicated alpha globin gene arrangement and heterozygous for beta thalassemia. Their differences in clinical phenotype are explainable by the interaction of other genetic factors and, in particular, their early management. The clinical course of the 2 propositi underlines the importance of full genotyping and a long period of observation before treatment is instituted, particularly in patients with beta thalassemia intermedia associated with extended alpha globin gene arrangements. The hemoglobin (Hb) F levels in these patients with severe beta thalassemia intermedia, compared with other forms of this condition in the Sri Lankan population and elsewhere, are unusually low, a consistent finding in extended alpha globin gene interactions and in dominant beta thalassemia, raising the possibility that increased levels of HbF production in beta thalassemia may require mutations at both beta globin gene loci.

Thalassemia in Sri Lanka: a progress report.

The thalassemias pose an increasing burden for health-care services in many Asian countries. In order to conserve rare resources, it is essential to determine the reasons for the remarkable phenotypic heterogeneity and natural history of these disorders so that the most cost-effective methods for their control and management can be established. A long-term observational study of patients with different forms of thalassemia in Sri Lanka suggests that in addition to the well-defined primary, secondary and tertiary genetic modifiers, environmental factors, particularly malaria, and variation in the ability to adapt to the profound anaemia which characterizes these conditions, may play a significant role in determining their clinical severity. These findings may have important implications for the control and management of thalassemia in Asian populations.

The molecular basis for the thalassaemias in Sri Lanka.

The beta-globin gene mutations and the alpha-globin genes of 620 patients with the phenotype of severe to moderate thalassaemia from seven centres in Sri Lanka were analysed. Twenty-four beta-globin gene mutations were identified, three accounting for 84.5% of the 1240 alleles studied: IVSI-5 (G-->C) 56.2%; IVSI-1 (G-->A) 15.2%; and haemoglobin E (codon (CD)26 GAG-->GAA) 13.1%. Three new mutations were found; a 13-bp deletion removing the last nucleotide in CD6 to CD10 inclusively, IVSI-129 (A-->C) in the consensus splice site, and a frame shift, CD55 (-A). The allele frequency of alpha+ thalassaemia was 6.5% and 1.1% for -alpha3.7 and -alpha4.2 deletions respectively. Non-deletion alpha-thalassaemia was not observed. Triplicate or quadruplicate alpha-globin genes were unusually common. In 1.5% of cases it was impossible to identify beta-thalassaemia alleles, but in Kurunegala detailed family studies led to an explanation for the severe thalassaemia phenotype in every case, including a previously unreported instance of homozygosity for a quadruplicated alpha-globin gene together with beta-thalassaemia trait. These findings have implications for the control of thalassaemia in high-frequency populations with complex ethnic histories.