People of East Indian descent account for 40% of the Trinidad and Tobago (TT) population. Most came from Uttar-Pradesh and West Bengal in India where thalassaemia is prevalent. The thalassaemia carrier frequency and exact mutations are unknown in TT. Diagnostic DNA analysis is not routinely available. Objective: To estimate the carrier frequency of thalassaemia among prospective blood donors. Method: Blood samples were obtained from 125 prospective blood donors of East-Indian origin. CBC was

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... e to screen for microcytosis(MCV≤83 fL). Microcytic samples had ferritin, transferrin saturation, haemoglobin electrophoresis, haemoglobin A2/F quantification and DNA analysis performed performed for thalassaemia. Results: 72.4% subjects were male and 26.4% female. Microcytosis was found in 14 (11.2%) (9 males, 5 females). Among microcytic subjects, 11(78.6%) (8 males, 3 females) thalassaemia mutations were detected. The range MCV range was wider in β-thalassaemia (63.7-80.7 fL) than α-thalassaemia carriers (78.5-80.1 fL). All subjects with the α-globin gene mutation had the α3.7 deletion which is the commonest α-gene mutation in India. The people with β-thalassaemia mutations had IVS I-5 G/C (common in India) and IVS II-666 T/C. Conclusion: There were a high percentage of thalassaemia carriers in microcytic individuals, thus showing the importance of testing for this disorder. A larger study is needed to determine the spectrum of α-and β-thalassaemia mutations, to analyze for correlation between the degree of microcytosis and specific genotype and for useful predictors of α-and β-globin gene mutations.