δβ-Thalassemia trait: how can we discriminate it from β-thalassemia trait and iron deficiency anemia?

Objectives: To analyze the differences not only in classic hematologic parameters but also in RBC subpopulations among δβ-thalassemia trait (δβ-TT), β-thalassemia trait (β-TT), and iron deficiency anemia (IDA) and to evaluate the role of fetal hemoglobin (HbF) in elevated RBC distribution width (RDW).

Methods: Samples from 553 patients with microcytosis (74 δβ-TT, 272 β-TT, and 207 IDA) were run on an Advia 2120i analyzer (Siemens Medical Solutions Diagnostics, Tarrytown, NY). Classic hematologic parameters and RBC subpopulations were assessed. The correlation between HbF and RDW in patients with thalassemia (both β and δβ) was evaluated. An independent sample t test was used to compare classic hematologic parameters and RBC subpopulations among β-TT, IDA, and δβ-TT and receiver operating characteristic curves performed in the significant comparisons.

Results: RDW was significantly higher in δβ-TT compared with β-TT (18.79% vs 16.04%, P < .001), as was mean corpuscular volume (66.39 vs 64.82 fL, P < .001), mean corpuscular hemoglobin (20.73 vs 20.04 pg, P < .001), and mean corpuscular hemoglobin concentration (31.16 vs 30.66 g/dL, P = .03). Pearson coefficient showed a good correlation between HbF and RDW. The values obtained for all the parameters were significantly different (P < .001) between patients with thalassemia (β and δβ) and IDA.

Conclusions: RDW is the best parameter to discriminate δβ-TT from β-TT. The degree of anisocytosis in patients with β-TT and δβ-TT is strongly correlated with HbF.