The REMA score, together with analyzing for a KIT D816V mutation in peripheral blood, could improve the identification of clonal mast cell disease (CMD), including systemic mastocytosis (SM) and monoclonal mast cell activation syndrome, in patients with wasp venom allergy presenting with a normal basal serum tryptase (bsT) level.

“Five years of venom immunotherapy provides lasting protection against new episodes of anaphylaxis. Unfortunately, this does not apply to patients with underlying CMD,” the study’s authors explained in Clinical Translational Allergy.

CMD patients have a lifelong indication for venom immunotherapy due to the possibility of severe, or even fatal, reactions after treatment discontinuation. Therefore, identifying CMD among patients with wasp venom allergy is of the utmost importance.

Sensitivity and specificity of the REMA score was 71.9% (95% CI, 56.0%-87.8%) and 78.7% (95% CI, 70.3%–87.2%), respectively, in patients with normal bsT. Sensitivity of the REMA score was even higher in patients with elevated bsT (92.3% [95% CI, 85.1%-100%]), but specificity was low (40.0% [95% CI, 9.6%-70.4%]).

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The analysis of the KIT D816V mutation in peripheral blood showed a specificity of 100%, although the sensitivity was relatively low (55.6% [95% CI, 36.4%-74.7%]), particularly in patients diagnosed with monoclonal mast cell activation syndrome. Subsequent analysis of the KIT D816V mutation in patients with a low REMA score improved the identification of missed CMD cases. On the other hand, the diagnosis of hereditary alpha tryptasemia did not provide any value in CMD risk assessment.

In addition, multivariate analysis identified loss of consciousness during systemic reactions and higher bsT levels (≥6.3 ng/mL) as parameters independently associated with CMD.

The study enrolled 186 patients with grade IV wasp venom allergy presenting with either normal (ie, <11.4 ng/mL, n=131) or elevated (ie, ≥11.4 ng/mL, n=55) bsT levels. Among the patients with normal bsT levels, 35 were diagnosed with CMD, with most (68.6%) having indolent SM. Most of the patients (81.8%) with elevated bsT had a CMD diagnosis.

The authors recognized 2 main study limitations: the inability to convert findings from the multivariate analysis into an adaptation of the REMA score and a certain overrepresentation of grade IVb reactions.

Reference

Onnes MC, Alheraky A, Nawijn MC, et al. Detection of clonal mast cell disease in wasp venom allergic patients with normal tryptase. Clin Transl Allergy. 2022;12(9):e12174. doi:10.1002/clt2.12174