Final answer:
The initial screening test for thalassemia is a complete blood count, which looks for low hemoglobin levels and abnormal red blood cell indices. This can be followed by hemoglobin electrophoresis and DNA testing for a definitive diagnosis.
Step-by-step explanation:
The initial test in screening someone with a possible thalassemia is a complete blood count (CBC). This evaluates the presence of anemia, characterized by low hemoglobin levels and abnormal red blood cell indices like mean corpuscular volume (MCV) and mean corpuscular hemoglobin (MCH). These indices are typically low in thalassemia.
Further testing can include a hemoglobin electrophoresis, which determines the types of hemoglobin present. In cases of β-thalassemia, there is a decrease in β-globin chains, leading to an increase in HbA2 and HbF. Additionally, DNA testing may be employed to detect mutations that cause β-thalassemia.
If immune-mediated hemolytic anemia needs to be ruled out, which may present similarly to thalassemia, a direct antiglobulin test (direct Coombs' test) can be conducted; however, it is expected to be negative in thalassemia as it is not immune-mediated.