Probability of anaphylaxis in patients with systemic mastocytosis
Anaphylaxis is a common feature in patients with mastocytosis. However, not all patients with mastocytosis experience anaphylaxis. A risk analysis model for anaphylaxis was translated into a clinical scoring system.
Research authors: Gülen T, Ljung C, Nilsson G, and Akin C.
Details Formula Study characteristics Files & References
Model author
Model ID
Revision date
MeSH terms
  • Mastocytosis
  • Clinical Prediction Rule
  • Anaphylaxis
  • Model type
    Linear model (Calculation)
    No Formula defined yet
    Condition Formula

    Additional information

    This study sought to determine risk factors for the occurrence of anaphylaxis in patients with SM. 

    A cross-sectional study was conducted in 122 consecutive adult patients with SM admitted to the Mastocytosis Center at Karolinska University Hospital. All patients underwent medical evaluation, including bone marrow biopsy and a thorough allergy workup. To determine risk factors, study subjects were categorized into 2 groups according to the presence (n [ 55) or absence (n [ 67) of anaphylaxis and compared for their demographic, clinical, and biochemical characteristics. 

    Patients with SM with anaphylaxis had less frequent presence of mastocytosis in the skin (P < .001), more atopic predisposition (P[.021), higher total IgE levels (P < .001), and lower baseline tryptase levels (27 ng/mL vs 42 ng/mL; P[.024) compared with patients with SM without anaphylaxis.

    Patients with SM with anaphylaxis display unique clinical and laboratory features. Hence, a risk analysis tool that is capable of discriminating patients with SM at high risk of anaphylaxis from those at low risk with 86% sensitivity
    was developed by using the variables male sex, absence of mastocytosis in the skin, presence of atopy, IgE levels of 15 kU/L or more, and baseline tryptase levels of less than 40 ng/ mL.

    Study Population

    Total population size: 122
    Males: {{ model.numberOfMales }}
    Females: {{ model.numberOfFemales }}

    Continuous characteristics

    Name LL Q1 Median Q3 UL Unit
    Age as of BM biopsy 20 54 84 years
    sBT levels 5.9 35 650 ng/ml
    Total IgE 1 13 1600 kU/l

    Categorical characteristics

    Name Subset / Group Nr. of patients
    Presence of multifocal MC clusters in BM No 49
    Yes 73
    KIT mutation D816V No 37
    Yes 85
    Presence of MIS No 83
    Yes 39
    Atopic predisposition No 26
    Yes 96
    Probability of anaphylaxis in patients with systemic mastocytosis
    Refer to Intended Use for instructions before use
    Evidencio B.V., Irenesingel 19, 7481 GJ, Haaksbergen, the Netherlands

    Total anaphylaxis risk score:

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    Total anaphylaxis risk score: points

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    Outcome stratification

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    Result interpretation

    How this model should be used:
    This risk assessment tool may provide a simple method of identifying and alerting patients with mastocytosis at high risk of anaphylaxis who would benefit from self-injectable epinephrine.

    Model performance:
    In the underlying study by Gülen et al (2017)1, a sensitivity of 86% (95% CI: 74.6 - 93.1%) and a specificity of 54% (95% CI: 41.8 - 65.4%) was observed in the development cohort (n=122). The corresponding postive predictive value (PPV) and negative predictive value (NPV) were 60.3% (95% CI: 49.2 - 70.7%) and 81.8% (95% CI: 68.6 - 91.2%), respectively. 


    1. Gülen T et al. Risk Factor Analysis of Anaphylactic Reactions in Patients With Systemic Mastocytosis. J Allergy Clin Immunol Pract. (2017).

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    Calculations alone should never dictate patient care, and are no substitute for professional judgement. See our full disclaimer.

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