A RECENT study has revealed an increased risk of venous thromboembolism (VTE) in individuals with sickle cell trait (SCT) compared to those without the trait. While SCT carriers face an elevated risk, the study found that the risk remains lower than for individuals with heterozygous factor V Leiden (FVL), the most common inherited blood-clotting disorder.
SCT is present in over 100 million people globally, including 7% of Black individuals in the USA. Unlike sickle cell disease (SCD), which involves two abnormal haemoglobin genes, SCT involves one sickle haemoglobin gene, and most carriers lead asymptomatic lives, however, SCT is a known risk factor for VTE. The study aimed to compare the VTE risk in SCT to FVL independent of race or genetic ancestry.
Analysing data from more than four million 23andMe participants, researchers discovered that while SCT was more prevalent among people of African descent, the risk of VTE in SCT carriers was not limited to any specific racial group. The risk was found to be 1.45 times higher than in non-carriers. Notably, the risk of pulmonary embolism (PE) in SCT carriers was nearly twice that of isolated deep vein thrombosis (DVT), suggesting a unique mechanism of clotting in these individuals. This PE-predominant pattern is opposite to FVL carriers, who have a higher risk of DVT than PE.
FVL carriers showed a 3.3-fold increased VTE risk, significantly higher than SCT carriers. These findings emphasise the need for clinicians to recognise SCT as a risk factor for blood clots across all populations, not just Black individuals, to avoid reinforcing racial biases in medical research.
The study opens new avenues for investigating the unique mechanisms of clotting in SCT and calls for more inclusive research to develop better clinical guidelines. Despite the elevated VTE risk, SCT remains a smaller risk factor compared to FVL, but its PE-specific clotting pattern suggests a need for further research.
Katie Wright, EMJ
Reference
Lin KH et al. Ancestry-Independent Risk of Venous Thromboembolism in Individuals with Sickle Cell Trait vs. Factor V Leiden. Blood Adv. 2024;DOI:10.1182/bloodadvances.2024014252.
