Routine screening for α-thalassaemia using an immunochromatographic strip assay for haemoglobin Bart's

Objective: To evaluate an immunochromatographic (IC) strip assay for Hb Bart's as a routine screening test for alpha-thalassaemia in area with a high prevalence of thalassaemia and haemoglobinopathies. Methods: A total of 300 adult screen positive blood specimens were collected at an ongoing thalassaemia screening programme in northeast Thailand. Routine screening was done using red blood cell indices, osmotic fragility, and dichlorophenolindophenol tests. The IC strip assay for haemoglobin Bart's was performed on all samples. The result was evaluated against thalassaemia genotypes determined using standard haemoglobin and DNA analyses. Results: Of 300 subjects investigated, Hb and DNA analyses identified 32 with normal genotype. The remaining subjects carried thalassaemia with as many as 16 different genotypes. Hb Bart's was detected in all cases, with several alpha(0)-thalassaemia (SEA type) related disorders. Of cases with alpha(+)-thalassaemia, 86.1% showed a positive result; 100 out of 103 Hb E carriers, all homozygous Hb E and beta-thalassaemia trait were negative. Nine out of 17 cases with beta-thalassaemia/Hb E disease, and one case of double heterozygote for Hb Q-Thailand and Hb E returned positive results. The overall sensitivity and specificity of the IC strip assay for detecting alpha(0)-thalassaemia were 100% and 73.1%, respectively. Conclusion: The results showed a high sensitivity for screening for alpha(0)-thalassaemia using IC strip assay for Hb Bart's. This simple method, used in combination with conventional screening protocols, should lead to a significant reduction in the number of referral cases for DNA analysis. Cost effectiveness in each population should be taken into consideration.