Prevalence of Severe Thalassemia and Performance of Prenatal Screening Tests Among Pregnant Women at Siriraj Thalassemia Center in Thailand

Severe thalassemia remains a significant public health concern in Southeast Asia. Prenatal screening is an effective strategy for early detection and prevention. This study aimed to determine the prevalence of severe thalassemia and assess the performance of prenatal screening at the Siriraj Thalassemia Center, Siriraj Hospital, Thailand. A retrospective review was conducted using data from January 2018 to December 2023. A total of 18,976 pregnant women underwent initial screening with mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and hemoglobin (Hb) typing. Of these, 12,499 tested positive. Complete screening data from 6,698 male partners identified 18.3% of couples as high-risk. Deoxyribonucleic acid (DNA) analysis and prenatal diagnostic testing were performed for at-risk pregnancies. Among high-risk couples, 75.2% of fetuses were identified by DNA analysis as being at risk for severe thalassemia, and 34.2% were confirmed as affected. The distribution of severe thalassemia types included Hb Bart's Hydrops Fetalis (15.8%), homozygous β-thalassemia (1.6%), and β-thalassemia/Hb E disease (16.8%). The most frequent α-thalassemia genotype in Hb Bart's cases was homozygous α⁰-thalassemia (--^SEA/--^SEA; 96.3%). The most common β-thalassemia mutation was a 4-base pair deletion at codons 41/42 (-TTCT; 40.2%). DNA testing for α-thalassemia showed 100% specificity and positive predictive value (PPV). For β-thalassemia, the sensitivity, specificity, PPV, and negative predictive value (NPV) were 97.6%, 98.9%, 96.1%, and 99.3%, respectively. The findings underscore the effectiveness of prenatal screening and diagnosis in identifying severe thalassemia, highlighting their importance for informing prevention strategies and guiding public health planning in high-prevalence settings.