The Red Española de Mastocitosis score (REMAs) might be more accurate in detecting mast cell clonality in systemic mastocytosis (SM) than the National Institutes of Health idiopathic clonal anaphylaxis score (NICAS-NIH), according to a team of researchers from Portugal and Spain.

“The combined use of the REMAs and blood detection of KITD816V is recommended, but more sensitive blood-based molecular assays for detection of KITD816V are still needed,” the study team wrote in The Journal of Allergy and Clinical Immunology: In Practice.

Their study enrolled 182 patients (median age, 55 years, age range, 10-81 years, 63% male) with mast cell activation syndrome. Most (73%) patients were diagnosed with clonal mast cell activation syndrome, including indolent SM (65%) and monoclonal mast cell activation syndrome not fulfilling the diagnostic criteria for mastocytosis (8%).

The accuracy of REMAs and NICAS-NIH was 82% and 75%, respectively, when considering the entire study cohort. The REMAs had higher sensitivity (90% vs 82%), specificity (63% vs 57%), positive predictive value (86% vs 83%), and negative predictive value (71% vs 56%).

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REMAs and NICAS-NIH classified 84% and 75% of patients correctly, respectively. The better performance of the REMAs was particularly noted for males, SM patients, and patients presenting with anaphylaxis due to any cause featuring urticaria, cardiovascular symptoms, and/or presyncope, as well as those with a blood/bone marrow+ KIT mutational profile. However, the REMAs did not outperform the NICAS-NIH in cases of α-tryptasemia-associated genotypes.

The proportion of SM patients correctly classified by the REMAs and the NICAS-NIH was 92% and 85%, respectively.

In addition, the classification efficiency of the REMAs was improved (from 84% to 86%) by adding KITD816V mutation information.


Rama TA, Torrado I, Henriques AF, et al. Mast cell activation syndromes: comparison between two scoring models to predict for mast cell clonality. J Allergy Clin Immunol Pract. Published online December 16, 2022. doi:10.1016/j.jaip.2022.11.042