Neonatal screening for haemoglobin variants using filter paper-dried blood specimens

The Use of Dried Blood Spots: A Potential Tool for the Introduction of a Neonatal Screening Program for Sickle Cell Anemia in Zambia

Context

Sickle cell disease is a group of hemoglobin (Hb) disorders resulting from the inheritance of the sickle β-globin gene. It is the most common pathological Hb mutation worldwide with 75% being born in Sub-Saharan Africa.

Aims

This study aims to determine if dried blood spots (DBSs) can be used for diagnosis of sickle cell in newborns. In Zambia, there is no neonatal screening program for sickle cell anemia (SCA), yet it has been proved that early diagnosis by newborn screening (NBS) using DBSs and access to comprehensive care results in survival to adulthood of over 96% of sickle cell patients.

Settings and Design

A cross-sectional study was carried out at the University Teaching Hospital to determine whether DBSs can be used to diagnose sickle cell using Hb electrophoresis.

Subjects and Methods

Results from DBSs stored for 2 weeks were then compared to those obtained using freshly collected whole blood.

Statistical Analysis Used

To evaluate performance characteristics, the following values were used: true positive, false positive, true negative, and false negative.

Results

Ninety-seven participants were included in this study. DBSs had a sensitivity of 100%, a specificity of 94.7%, positive predictive value of 96.7%, negative predictive value of 100%, overall efficiency of 97.9%, and a Kappa r², P < 0.0001 in comparison to fresh whole blood which we used as the gold standard.

Conclusions

The use of DBSs can be recommended for NBS of SCA in Zambia due to its high sensitivity, specificity, and stability of hemoglobin.

Advances in technologies for screening and diagnosis of hemoglobinopathies

Hemoglobinopathies constitute the most common monogenic disorders worldwide, caused by mutations in the globin genes that synthesize the globin chains of hemoglobin. Synthesis may be reduced (thalassemia) or underlie abnormal hemoglobins. Mutation interactions produce a wide range of disorders. For neonatal and antenatal screening, identification of affected newborns or carriers is achieved by hematological tests. DNA analysis supports definitive diagnosis, and additionally facilitates prenatal diagnosis procedures. Most methods used today have been developed over several decades, with few recent advances in hematology methods. However, DNA methods evolve continuously. With global migration and multiethnic societies the trend is from targeted, population-specific methods towards generic methods, such as Sanger sequencing (point mutations) and multiplex ligation probe amplification (deletions). DNA microarrays constitute an advanced DNA method for some mutation categories. The newest DNA technology is next-generation sequencing. Although not completely ready for routine use currently, next-generation sequencing may soon become a reality for some hemoglobin diagnostic laboratories.

3-years experience review of neonatal screening for hemoglobin disorders using tandem mass spectrometry

BACKGROUND

Neonatal screening programs for sickle cell disease are common in North America and in some European countries. Isoelectric Focusing or High Performance Liquid Chromatography is the main technique used for hemoglobin variant detection.

METHODS

Since tandem mass spectrometry is being used for screening of inherited metabolic disorders and allows protein identification, we had developed an application to identify the most relevant hemoglobin mutations with this technology.

RESULTS

This approach had been previously validated and has been routinely applied in our laboratory for the last three years. We report here our experience with this new method in the field, applied to our East-Belgian population.

CONCLUSIONS

To conclude, mass spectrometry provides an efficient alternative approach for laboratories performing neonatal screening of hemoglobin disorders.

The use of the dried blood spot sample in epidemiological studies

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