Researchers have identified a new serum biomarker – the extracellular domain of NOTCH3 – that can identify individuals with idiopathic pulmonary arterial hypertension. This protein biomarker correlates with disease progression and improves the prediction of mortality risk in patients with this serious disease. The main advantage of the discovery is that it enables an easily implemented non-invasive blood test for the diagnosis of pulmonary arterial hypertension. The research was published in the prestigious journal Nature Medicine and represents a significant advance in the diagnosis of this disease. The new test could improve the early detection of the disease and enable better monitoring of its development in patients. The NOTCH3 biomarker thus represents a prospective tool for clinical practice in the treatment of pulmonary arterial hypertension.