Estimated Prevalence of β-Thalassemia in the United States in 2023

Introduction: The number of β-thalassemia (BT) prevalent cases in the US was previously estimated at 2,600 and state-specific prevalence data are limited. Here, we use newborn screening data to estimate the current number of BT and transfusion dependent β-thalassemia (TDT) cases in the US.

Methodology: We requested results for newborn screening data for BT from 26 state public health programs. The goal was to estimate the total number of clinically significant BT cases that included BT subgroups: β-thalassemia major (BTM), β-thalassemia intermedia (BTI), and hemoglobin E β-thalassemia (HbEBT). As BT primarily affects individuals of Mediterranean and Southeast Asian ancestry, and very few cases are expected to occur in smaller states with relatively homogeneous US-born populations, we included states with at least 500,000 foreign-born residents, or states with a population of at least 5 million. Due to how the states’ data collection and reporting varied, cases were standardized into BTM, BTI, and HbEBT consistent with reporting in the literature. The total prevalence of BT in the US in 2023 was estimated using a modified life table model based on the median US birth incidence for all BT groups and survival probabilities. State-specific BT birth incidence and the median for the census region were used in a sensitivity analysis. Additional sensitivity analyses using varying definitions of TDT were conducted.

Results: Based on 17 states reporting data sufficient for analysis, the national median BT birth incidence was 1.46 cases per 100,000 live births. When applying the US median birth incidence to all states in the life table model, the total number of BT cases in the US in 2023 was 3,665, equivalent to 1.07 per 100,000 persons. However, based on sensitivity analyses the estimated prevalence was as high as 4,214 cases (1.23 per 100,000). The number of prevalent TDT cases was 2,611 and as high as 3,036 in sensitivity analyses.

Conclusion: Our results suggest that the previously reported number of 2,600 individuals receiving care for thalassemia in the US is likely an underestimate. Variations observed in the reported BT birth incidence by state could be due to true population differences as well as variation in newborn screening reporting. More research is needed to understand the epidemiological trends of BT in the US as the implications of undercounting BT cases are significant when considering healthcare resource planning.