Genetic testing has always been central to the thalassemia patient journey. However, conventional testing methods present a range of challenges to both laboratory directors and physicians.
Testing for thalassemia usually involves a patchwork of methods, from PCR to MLPA, to check for all possible changes. Not only is this a lengthy and complicated process, but it comes with a higher risk of variant non-detection and sample contamination. Considering the current patterns of thalassemia, we can no longer afford to accept these issues.
In the past, certain variants were restricted to specific populations. For example, β-thalassemia would be expected in people of Mediterranean descent (the disease was even once known as Mediterranean anemia). Today, migration flows have shifted prevalence and we are seeing β-thalassemia in regions where it was previously a rare disease.
Next-generation sequencing (NGS) testing can be used for simultaneous analysis of HBA and HBB gene clusters. It can be performed as a simple, rapid, one-tube reaction that streamlines testing procedures and provides higher quality results.
NGS technology has revolutionized genomic research and clinical genetics. Parallel sequencing of small DNA fragments allows us to capture a broader range of variants in a single test. In comparison, traditional Sanger sequencing only detects small insertions, deletions, and substitutions. To detect additional changes, you have to add more methods to the workflow. This is why conventional thalassemia testing requires a multi-step process to cover all the potential variants. It is also why it frequently misses.
In a recent study, the Devyser Thalassemia NGS assay was applied to a number of samples with pathogenic globin gene variants. In 15% of them, NGS detected additional variants that traditional workflows had not revealed. Why? In a conventional setting, the workflow might stop as soon as a pathological variant is detected. With NGS, however, all gene clusters are interrogated simultaneously. Because it provides comprehensive analysis on the first try, NGS sequencing reduces undetected variants and provides clinicians and patients with robust information.
NGS is free of bias because it does not rely on prior knowledge of common variants. As thalassemia patterns change, our notions of "what to expect" are becoming more and more obsolete. NGS gives you a bird's eye view of gene clusters, which is something we increasingly need.