Thalassemia Screening Using Different Automated Blood Cell Counters: Consideration of Appropriate Cutoff Values

Background: To evaluate the use of MCV and MCH cutoffs for thalassemia screening in areas with a high frequency of thalassemia and hemoglobinopathies using different hematology analyzers. Methods: Blood samples of known alpha(0)-thalassemia and beta-thalassemia carriers were analyzed to establish the appropriate cutoffs for each analyzer. These selected cutoffs were validated prospectively for screening of alpha(0)-thalassemia, beta-thalassemia in combination with the dichlorophenolindophenol test for hemoglobin E on another 288 Thai and 325 Laotian students. Genotypes were defined by standard hemoglobin and DNA analyses. Results: The appropriate cutoffs for the Sysmex XS-800i and Sysmex XN-1000, Coulter LH 780, and Pentra ES-60 were found to be 78 IL for MCV and 25 pg for MCH. These were 82 fL and 25 pg for the Cell-Dyn Ruby. Further validation on Thai and Laotian students revealed 100% sensitivity and specificity of higher than 80% for all analyzers. Conclusions: While using MCV in screening requires establishment of appropriate cutoffs, MCH appears to be applicable to all analyzers. Each analyzer should be evaluated and appropriate cutoffs should be established before application in the field.