Assessment of β-Thalassemia Trait Occurrence in an Outpatient Sample from Southern Chile: A Retrospective Study

<b>Background/Objectives:</b> Thalassemia comprises a group of heterogeneous hereditary hemoglobinopathies characterized by impaired hemoglobin synthesis due to mutations in the α, β, and/or δ globin genes. The resulting ineffective erythropoiesis produces anemia of variable severity depending on the affected globin chain. Although β-thalassemia is most prevalent in the Mediterranean region, the Middle East, and Southeast Asia, migration has contributed to its global spread, including in non-endemic areas. In Chile, published data on β-thalassemia trait (BTT) and β-thalassemia major (BTM) remain scarce. This study aimed to estimate the frequency of BTT in referred outpatients to a clinical laboratory in southern Chile. <b>Methods:</b> A retrospective observational study was conducted between January 2021 and November 2024 at a clinical laboratory in Puerto Montt. Complete Blood Cell counts (CBCs) from unique patients were reviewed, and those confirmed with confirmed thalassemia (HbA2 > 3.5%) were selected. <b>Results:</b> During the study period, 24,634 CBCs were reviewed. Sixty patients were confirmed as carriers of BTT, corresponding to a frequency of 0.24% (CI 95%: 0.18-0.31%) in the referred outpatients to laboratory (60/24,634). This occurrence is higher than the only previously published Chilean estimate but lower than frequencies reported in several South American countries. <b>Conclusions:</b> This investigation demonstrates a relatively low but non-negligible frequency of BTT in outpatients from southern Chile. The findings emphasize the importance of considering BTT in the differential diagnosis of microcytic anemia, a condition often underestimated in routine practice. Broader multicenter studies across Chile are warranted to validate these results and to provide a clearer picture of the epidemiology of β-thalassemia in the country.