Dear Editor, the recent report on “hematocrit (HCT) level and cardiovascular risk among Thai taxi drivers” is very interesting1). Ishimaru et al. concluded that “obesity (p=0.007), daily alcohol drinking (p=0.003), and current or past smoking (p=0.016) were associated with higher HCT levels1).” In fact, it is no doubt that the mentioned factors are related to HCT level. In Thailand, where Ishimaru et al. performed the study1), the thalassemia and hemoglobin (Hb) disorder (e.g. Hb-E) is very prevalent (estimated 30% of the local people are carriers of the disorder)2) and this is an important confounding factor that results in an aberrant HCT level. Indeed, the similar problem (thalassemia and hemoglobin disorder) is also common in many areas of the world such as in South Asia, Mediterranean and Africa and there is a similar concern on interpretation of HCT level and cardiovascular risk. In cases with underlying Hb disorder, there might be a low HCT background and the relationship between HCT level and cardiovascular risk should be assessed. In a recent report, the thalassemicpatients with a cardiovascular problem usually have lower pre-transfusion HCT level3). Chen et al. recently reported the association between “coronary artery disease (CAD)” and HCT level in thalassemia patients4). Chen et al. noted that “the overall risks of developing CAD were 1.5-fold in patients with thalassemia compared with those in the comparison cohort after adjustment for age, sex, and comorbidities4).” If one has an underlying of thalassemia/Hb disorder with low HCT, the risk of coronary thrombosis is still high.