Predictors of Thalassaemia Carriers in Trinidad and Tobago

Objective: To determine possible predictors of thalassaemia carriers among prospective blood donors in Trinidad and Tobago

Background: Thalassaemias are prevalent in India, South-East Asia, Mediterannean, Middle East and respective migrants. Trinidad ad Tobago (TT) has 1.3million people (34.2% African origin, 35.4% Indian origin, 22.8% mixed heritage, (and the rest include Caucasian, Chinese and indigenous people). DNA analysis for thalassaemia diagnosis/neonatal/population screening is not routinely available. Simple inexpensive thalassaemia predictors are needed. The main indicator is microcytosis, the commonent differential of which is Iron Deficiency Anaemia (IDA). Tiwari(2009), showed 5.4% microcytosis among Indian blood donors. (52%-IDA, 36%-Beta-thalassaemia trait, 8%-mixture of both, 4% neither). Combinations of RBC-parameters improve discriminative powers (Urechaga, 2013). No similar studies have been done in TT.

Design and Methods: 460 prospective blood donors were screened for microcytosis (MCV<83fL) by performing a CBC using a Sysmex XE-2100. Microcytic samples further had blood film analysis, iron studies, haemoglobin electrophoresis, haemoglonin F/A2 quantification, and DNA analysis for thalassaemia mutations. SPSS stastitical analysis was performed to determine predictors of thalassaemia trait. Variables tested were ethnicity, haemoglobin, MCV, MCH, MCHC, RBC (RCC), RDW-SD, and RDW-CV. Mathematical formulae were also used ie the Mentzer, Shine and Lal, Green and King, and Srivastava Indicies.

Results: 86(18.7%) subjects had microcytosis. 44 of these had DNA results. 22(50%) had MCV between 80-83fL. 31(70.5%) had thalassaemia trait: 25(80.6%) with genotype -α/αα, 4(12.9%) α-/α-(all α^3.7), one IVS I-5 G/C and one IVSII-666 T/C. The MCV, RDW-SD and RDW-CV were useful in predicting thalassaemia trait. RDW-SD identified 30(96.8%) of the 31 carriers, the Green and King formula identified 27 (87.1%), and Ricerca index identified all 31.

Conclusion: MCV, RDW-SD, Green and King formula and Ricerca index may be useful predictors of thalassaemia trait in Trinidad and Tobago. A higher cut off for MCV (83fL as opposed to the 72fL or 78fL usually used for screening purposes), improves the thalassaemia-trait pick up rate.

(Acknowledgments: ^aMarie-D Hardy-Dessource, ^bChristian Saint-Martin, ^aMarc Romana - (^aINSERM S_763, CHU de Pointe-à-Pitre, Pointe-à-Pitre, Guadeloupe: ^bLaboratoire de l'Unité transversale de la Drépanocytose, CHU de Pointe-à-Pitre, Pointe-à-Pitre, Guadeloupe)