A New Methodology To Screen Hemoglobinopathies Using Capillary Blood Samples.

The prevalence of β-thalassemia carriers among the Portuguese was around 2–3%, but nowadays, due to the immigrant populations coming from Africa, Brazil, East Europe and Asia, with different forms of thalassemias and Hb variants, hemoglobinopathies are much more common and with different genetic characteristics. Concerned with the risk of having an increasing number of patients with the severe forms of hemoglobinopathies, we decided to screen carriers, after personal informed consent, among pregnant women until 18-weeks of gestation and young adults attending primary care services. The goal of the project is to screen approximately 50000 blood samples in order to:

1. know the hemoglobinopathies frequency and heterogeneity in the population living in Central Portugal (~2500000 inhabitants), and, based on these data, to develop a future cost/effective strategy for carrier identification;

2. identify carriers to provide genetic information and counseling.

In primary care medical centers there are no facilities to collect venous blood samples and we needed to establish a methodology to identify Hb variants and to correctly quantify HbA₂ and Hb F in capillary blood samples, which has to be send by ordinary mail to our Lab Center. Working with the “HbA_1c Capillary Collection System” from BioRad, we settled an accurate procedure to perform HPLC analysis on capillary blood stored at room temperature until 7 days after collection. To validate the technique we tested, in diverse conditions, more than 200 random and known controls samples: for the same individuals, HPLC results in capillary blood, collected with this system, and in EDTA peripheral blood samples, were identical. This methodology will detect β- and δβ-thalassemias and Hb variants; molecular characterization can be done through blood spots in filter paper (Guthrie spots) collected at the same time. Within 24–48 hours after sample reception in the Lab, results are reported to the respective physician, who is going to establish the correlation with the hematological parameters.

Carriers identified through the screening will be urged to have their partner tested. If they are both carriers, they will be sent to our out patient clinic in order to evaluate the risk of having a child with a clinically significant hemoglobinopathy. If indicated, underling mutation will be identified, genetic counseling provided and prenatal diagnosis offered.

The project, supported by the national program Saúde XXI/FEDER/FSE, started last April, was preceded by training sessions for doctors and nurses working in primary care centers and maternity hospitals. Brochures and posters are distributed for public information. As reported in some European surveys, we are willing to be effective in preventing the birth of affected infants with sickle cell disease and severe forms of thalassemia in Portugal.