New research reassessing how accurately the Spanish Network on MastocytosisMastocytosis Rare disease caused by the buildup of mast cells. Cutaneous mastocytosis primarily affects the skin and is more common in children, while systemic mastocytosis affects internal organs and is more common in adults. (REMA) score identifies people who may have clonal mast cell activationMast cell activation Describes when mast cells release histamine and other mediators into the blood stream in response to an allergen or other trigger. This leads to symptoms like fatigue, rash and, in severe cases, anaphylaxis. disorders, including systemic mastocytosis (SM), proposed updates to improve its ability to identify which patients may need further testing. The findings were recently published in the journal Allergy.
The REMA score is a clinical tool used to estimate whether severe mast cellMast cell A type of white blood cell produced in the bone marrow. They help defend against infections and play a key role in allergic reactions. In SM, mast cells become overactive and build up throughout the body. mediator-related symptoms, such as anaphylaxisAnaphylaxis A severe allergic reaction that can turn fatal without treatment. Patients with SM are at a higher risk of developing anaphylaxis., may be linked to an underlying clonal mast cell disorder. In these disorders, mast cells show abnormal features, such as certain genetic changes or unusual cell markers, that may contribute to recurrent or severe reactions.
For about 15 years, doctors have used the REMA score to help decide which patients should undergo bone marrow testing. Bone marrow testing can help confirm the presence of abnormal mast cells in the bone marrow, a key sign of a clonal mast cell disorder, but it is invasive and not practical for every patient with suspected mast cell activation.
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In the study, researchers reviewed data from 1,204 adults referred to the Spanish Network on Mastocytosis between 2007 and 2024. All patients had severe mast cell mediator-related symptoms, most often anaphylaxis, but did not have mastocytosis in the skin. Researchers analyzed clinical features, baseline tryptaseTryptase A protein enzyme that is primarily produced by mast cells and stored in small pockets within the cells, known as granules. High levels of tryptase are a key indicator of SM. levels, bone marrow findings, immunophenotyping and testing for KIT mutations.
Clonal mast cell activation disorders were diagnosed in 64% of patients who underwent bone marrow testing. These included SM and monoclonal mast cell activation syndrome, a related condition in which mast cells show clonal features but do not meet full criteria for mastocytosis.
The original REMA score remained highly sensitive, meaning it was good at identifying people who may have clonal mast cell diseaseMast cell disease A group of conditions in which mast cells behave abnormally by building up in excess, releasing chemicals too easily or both. Includes mastocytosis, mast cell activation syndrome and hereditary alpha-tryptasemia.. However, it had limited specificity, meaning it was less effective at ruling out clonal disease in people who did not have it. The score was least accurate in patients with intermediate scores from 0 to 2.
To improve the tool, researchers proposed a refined algorithm. Under the updated approach, bone marrow testing is recommended for patients with a REMA score greater than 2. For patients with scores from 0 to 2, testing may also be recommended if they have insect venom-triggered anaphylaxis or elevated baseline tryptase without hereditary alpha tryptasemia, a genetic trait that can raise tryptase levels. Testing is also supported when the KIT D816V mutation is detected in blood in patients with scores of 2 or lower.
The refined algorithm improved specificity to 57% while maintaining sensitivity at 86%, with an overall accuracy of 75%. Researchers said the updated approach may help doctors better select patients for bone marrow testing while reducing unnecessary invasive procedures.
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