Tryptase values in anaphylaxis and insect allergy

Tryptase: The Silent Witness of Past and Ongoing Systemic Events

Introduction: Tryptase is an important biomarker widely used in the laboratory confirmation of severe hypersensitivity reactions, especially anaphylaxis. It also plays a crucial role in the diagnosis, risk stratification, management and prognostic evaluation of many other mast cell-related conditions. Aim: This paper aims to highlight the role of serum tryptase, both in allergic disorders and other mast cell-related conditions. Two clinical cases regarding timely serum tryptase acquisition (in drug hypersensitivity reactions during the imaging procedure and perioperative anaphylaxis) are meant to emphasize the clinical potential of this protease. Method: We performed a comprehensive literature search of the PubMed/Medline and Scopus databases. From a total of 640 subject related publications, dating from 1940 to 2024, 45 articles written in English were selected. Literature search results: Total serum tryptase is a simple, cost-effective analysis with a normal baseline tryptase (sBT) level below 8.4 µg/L. Elevated sBT can indicate hereditary alpha-tryptasemia (HαT), mastocytosis and other non-allergic disorders. Patients with higher sBT levels, especially with insect venom allergy, have an increased risk of severe reactions and thereby require a prolonged treatment. All immediate systemic hypersensitivity reactions require a correlation between serum acute tryptase (sAT) and sBT. According to the guidelines, measuring sAT 30 min to 2 h after the symptom onset and sBT 24 h after the resolution, using the 20 + 2 rule and an sAT/sBT ratio of 1.685, improves the diagnostic accuracy in anaphylaxis. Conclusions: Tryptase levels should be acquired in all cases with clinical suspicion of MC degranulation. Given the increasing clinical relevance, elevated baseline serum tryptase levels require a multidisciplinary approach and further investigation.

Remimazolam-Induced Anaphylaxis and Cardiovascular Collapse: A Narrative Systematic Review of Eleven Cases

Background and Objectives: Remimazolam, a novel benzodiazepine, is used for procedural sedation and general anesthesia due to its rapid onset and short duration of action. However, remimazolam-induced anaphylaxis (RIA) is a rare but severe complication. This study aimed to analyze RIA characteristics, focusing on cardiovascular collapse, and provide guidelines for safe remimazolam use. Methods: This study conducted a systematic review using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 guidelines. Research articles retrieved from PubMed on 26 May 2023, using the keywords 'remimazolam AND anaphylaxis' were evaluated based on the inclusion criteria of being written in English and aligning with the World Allergy Organization criteria for anaphylaxis, while studies not meeting these criteria were excluded. All published articles up to the search date were included without any date restrictions. The review analyzed factors such as age, sex, type of anesthesia, remimazolam dose (bolus/continuous), allergic symptoms and sign, epinephrine use, serum tryptase levels, and skin prick tests. Results: Among eleven cases, the mean age was 55.6 ± 19.6 years, with 81.8% male. Hypotension (81.8%) was the most common symptom, followed by bradycardia (54.5%) and desaturation (36.4%). Two patients experienced cardiac arrest. Serum tryptase levels confirmed anaphylaxis in ten cases. Epinephrine was the primary treatment, with intravenous doses ranging from 0.1 mg to 0.3 mg. Conclusions: Vigilance is crucial when administering remimazolam, adhering to recommended dosages, and promptly treating RIA with epinephrine. Further research is needed to understand the risk factors and refine the management strategies. Guidelines for safe remimazolam use are proposed.

Venom Anaphylaxis: Decision Points for a More Aggressive Workup

Diagnostic testing of patients who present for evaluation of insect venom allergy can involve many levels of investigation. A detailed initial history is critical for diagnosis and prognosis. The severity of previous sting reactions and the presence or absence of urticaria or hypotension predict severe future sting reactions and underlying mast cell disorders. Venom skin tests and specific IgE measurement can confirm the diagnosis but have limited positive predictive value for the frequency and severity of future sting reactions. Testing for serum IgE to recombinant venom component allergens can distinguish true allergy from cross-reactivity to honey bee and yellowjacket venoms. Basophil activation tests can improve the detection of venom allergy and predict the severity of reactions and the efficacy of venom immunotherapy but are limited in availability. An elevated basal serum tryptase level is an important marker for severe sting anaphylaxis and underlying mast cell disorders (eg, hereditary α-tryptasemia and clonal mast cell disease). When there is high suspicion (eg, using the Red Espanola de Mastocytosis score), bone marrow biopsy is the definitive tool to characterize mast cell disorders that are associated with the most severe outcomes in patients with insect sting allergy.

Anaphylaxis: Advances in the Past 10 Years

In the past 10 years, anaphylaxis has grown into its own special area of study within Allergy-Immunology, both at the bench and at the bedside. This review focuses on some of the most clinically relevant advances over the past decade. These include simplified and more inclusive diagnostic criteria for adults and children, uniform definition of biphasic anaphylaxis, and improved systems for objective severity grading. Studies reported in the past decade have led to improved understanding of normal and abnormal regulation of mast cell function, translating into better diagnostic and therapeutic approaches to patients with anaphylaxis. Research has provided improved recognition and treatment of mast cell disorders and has identified a new condition, hereditary α-tryptasemia, that may impact anaphylactic syndromes. We have learned to recognize new causes (α-gal), new pathways (Mas-related G protein-coupled receptor-X2), and many risk factors for severe anaphylaxis. The stability of epinephrine in autoinjectors was reported to be very good for several years after the labeled expiry date, and it can tolerate freezing and thawing. Repeated and prolonged exposure to excessive heat leads to degradation of epinephrine activity. New treatments to prevent severe anaphylaxis have been described, using new ways to block the IgE receptor or modulate intracellular signaling pathways.

Systematic comparisons of various markers for mast cell activation in RBL-2H3 cells

Mast cell activation plays a key role in various allergic diseases and anaphylaxis. Several methods/techniques can be used for detection of mast cell activation. However, there was no previous systematic evaluation to compare the efficacy of each method/technique. The present study thus systematically compared various markers for mast cell activation induced by IgE cross-linking. The widely used RBL-2H3 mast cells were sensitized with anti-DNP (dinitrophenyl) IgE overnight and activated with DNP-BSA (bovine serum albumin) for up to 4 h. The untreated cells and those with anti-DNP IgE sensitization but without DNP-BSA activation served as the controls. Intracellular calcium level gradually increased to ~2-fold at 1 h, reached its peak (~5-fold) at 2 h, and returned to the basal level at 3-h post-activation. The increases in cellular tryptase level (by Western blotting) (~0.3- to 0.4-fold) and average cell size (~2.5-fold) and decrease of nucleus/cytoplasm ratio (~0.4- to 0.5-fold) were marginal at all time-points. By contrast, β-hexosaminidase release and CD63 expression (by both flow cytometry and immunofluorescence detection/localization), secreted tryptase level (by Western blotting), and tryptase expression (by immunofluorescence detection/localization) stably and obviously increased (~10-fold as compared with the untreated control and sensitized-only cells or detectable only after activation). Based on these data, the stably obvious increases (by ≥ 10-fold) in β-hexosaminidase release, CD63 expression (by both flow cytometry and immunofluorescence staining), secreted tryptase level (by Western blotting), and tryptase expression (by immunofluorescence staining) are recommended as the markers of choice for the in vitro study of mast cell activation using RBL-2H3 cells.

Clinical utility of serum tryptase levels in pediatric anaphylaxis

Introduction: This study aimed to evaluate the preliminary diagnosis, demographic characteristics, and outcomes of patients whose serum total tryptase levels were measured while in a tertiary pediatric hospital and to ascertain the role of serum tryptase levels in the etiology, diagnosis, severity, and course of systemic anaphylaxis. Methods: Patients ages between 1 month and 17 years who were followed up in the pediatric emergency department or as inpatients and with a diagnosis of immediate-type reactions between September 1, 2019, and August 31, 2021, were included in the study. Patient data were obtained retrospectively by examination of medical records and patient observation forms. Results: It was determined that serum tryptase levels were measured in a total of 310 patients during the study period. One hundred and fifty-five patients who met the defined diagnostic criteria were named as the anaphylaxis group and their data were detailed. The serum tryptase elevation was detected in 15.5% of the patients among the samples that met the anaphylaxis diagnostic criteria. No relationship was found between the serum total tryptase levels, the triggering factor, and the severity of anaphylaxis. Discussion: Anaphylaxis is a complex syndrome that involves different phenotypes that develop with various triggers in which different immunologic pathways, cell types, and mediators play a role. Serial measurements, including the basal value measured at least 24 hours after the symptoms disappear, are useful to confirm the diagnosis and guide the diagnostic tests during the follow-up, especially allergy evaluation.

Aedes albopictus salivary proteins adenosine deaminase and 34k2 interact with human mast cell specific proteases tryptase and chymase

When mosquitoes probe to feed blood, they inoculate a mixture of salivary molecules into vertebrate hosts’ skin causing acute inflammatory reactions where mast cell-derived mediators are involved. Mosquito saliva contains many proteins with largely unknown biological functions. Here, two Aedes albopictus salivary proteins – adenosine deaminase (alADA) and al34k2 – were investigated for their immunological impact on mast cells and two mast cell-specific proteases, the tryptase and the chymase. Mouse bone marrow-derived mast cells were challenged with increased concentrations of recombinant alADA or al34k2 for 1, 3, and 6 h, and to measure mast cell activation, the activity levels of β-hexosaminidase and tryptase and secretion of IL-6 were evaluated. In addition, a direct interaction between alADA or al34k2 with tryptase or chymase was investigated. Results show that bone marrow-derived mast cells challenged with 10 μg/ml of alADA secreted significant levels of β-hexosaminidase, tryptase, and IL-6. Furthermore, both al34k2 and alADA are cut by human tryptase and chymase. Interestingly, al34k2 dose-dependently enhance enzymatic activity of both tryptase and chymase. In contrast, while alADA enhances the enzymatic activity of tryptase, chymase activity was inhibited. Our finding suggests that alADA and al34k2 via interaction with mast cell-specific proteases tryptase and chymase modulate mast cell-driven immune response in the local skin microenvironment. alADA- and al34k2-mediated modulation of tryptase and chymase may also recruit more inflammatory cells and induce vascular leakage, which may contribute to the inflammatory responses at the mosquito bite site.

Acute Urticaria and Anaphylaxis: Differences and Similarities in Clinical Management

Acute urticaria is a common condition that presents with wheals and/or angioedema. However, these symptoms are also frequent in anaphylaxis, a life-threatening reaction that should be immediately diagnosed and treated. In both, mast cells play a central role in the physiopathology. Causes and triggers of acute urticaria and anaphylaxis are similar in general, but some peculiarities can be observed. The diagnostic approach may differ, accordingly to the condition, suspicious causes, age groups and regions. Adrenaline is the first-line treatment for anaphylaxis, but not for acute urticaria, where H1-antihistamines are the first choice. In this paper, we review the main aspects, similarities and differences regarding definitions, mechanisms, causes, diagnosis and treatment of acute urticaria and anaphylaxis.

Fatal hymenoptera venom anaphylaxis by undetected clonal mast cell disorder: A better identification of high risk patients is needed

Hymenoptera venom anaphylaxis is the most frequent cause of anaphylaxis and responsible for about 20% of all fatal anaphylaxis cases in adults. We report two cases of fatal hymenoptera venom anaphylaxis with undiagnosed underlying mastocytosis and review the risk factors for severe or fatal hymenoptera venom anaphylaxis, as well as the specificities of its association with mastocytosis. As hymenoptera venom allergic patients with underlying clonal mast cell disorder generally lack typical skin lesions of mastocytosis, its diagnosis can easily be missed, underscoring the importance and need for diagnostic strategies in order to correctly identify these patients. Predominant cardiovascular symptoms in the absence of urticaria or angioedema following an insect sting are suggestive of underlying clonal mast cell disorder, and should be distinguished from panic attack or vasovagal syncope. Similarly, an unexplained syncope or an "idiopathic" anaphylaxis might reveal mastocytosis or hereditary alpha-tryptasemia. Acute and basal serum tryptase measurements should always be integrated in the diagnostic work-up of an insect sting reaction or unexplained syncope or shock of any origin.

Diagnostic performance of serial serum total tryptase measurement to differentiate positive from negative allergy testing among patients with suspected perioperative hypersensitivity

BACKGROUND

Serum total tryptase has been shown to increase during acute allergic reactions (acute tryptase, T_A ); however, few studies have investigated the values of T_A or a combination of T_A and baseline tryptase (T_B ) to discriminate positive from negative testing in perioperative hypersensitivity reaction (POH) allergy work up. The aim of this study was to determine the diagnostic performance of T_A in order to differentiate positive from negative allergy testing suspected POH and analyze the diagnostic performance of serial tryptase levels using several formulas.

METHODS

All patients from the University hospital of Montpellier and Strasbourg, France who presented with suspected POH and underwent complete drug allergy work-up between March 2011 and December 2019 with available T_A and T_B were included. Four formulas, including a change in T_A >11 (F1), or >2+1.2xT_B (F2), or >3+T_B (F3), or >120%T_B (F4), were applied.

RESULTS

One hundred and sixty-two patients were included, and 131 of them (80.8%) had grade III or IV reactions. Ninety patients had positive allergy testing. The optimal cut-off value of T_A to distinguish positive from negative allergy testing patients was 9.8 μg/L with an AUC of 0.817 (95%CI: 0.752-0.882, p<0.001). The 93% PPV threshold for T_A was 33 μg/L (95.8% specificity). Paired tryptase levels according to formulas F2 and F3 yielded the highest Youden index (0.54 and 0.53, respectively).

CONCLUSION

The optimal cut-off point for T_A for distinguishing positive from negative allergy testing suspected POH was 9.8 μg/L. T_A value of 33 μg/L was required to achieve >90% PPV.

Mast cell activation syndrome: is anaphylaxis part of the phenotype? A systematic review

PURPOSE OF REVIEW

Mast cell activation syndrome (MCAS) and anaphylaxis are the result of a spontaneous or triggered pathological degranulation of mast cells (MCs) and might have as substrate normal or pathological MCs (increased burden, aberrant MCs or both).

RECENT FINDINGS

This review summarizes the most recent evidence on immunoglobulin E (IgE)-mediated and non IgE-mediated mechanisms underlying MC activation and degranulation and highlights the importance of standardized diagnostic criteria for MCAS. Application of these criteria implies that in most cases the clinical presentation of MCAS meets the diagnostic criteria for anaphylaxis.

SUMMARY

Integrating clinical parameters and diagnostic test recognition and underlying clonal MC disease are of utmost importance for a patient-tailored approach. Hereditary alpha-tryptasemia can be encountered in context of anaphylaxis, MCAS and primary MC disorders.

Pregnancy and Hymenoptera venom allergy

PURPOSE OF REVIEW

To evaluate the indication to perform venom immunotherapy (VIT) during pregnancy considering the risks of adverse events during the build-up phase or the maintenance phase and analyzing specific articles and guidelines on VIT.

RECENT FINDINGS

Only few studies treat this argument and literature only counts one recent study on the topic, whereas recent guidelines state the behavior to keep in pregnancy.

SUMMARY

Hymenoptera venom allergy (HVA) affects about 7.5% of the European population. VIT is the only effective disease-modifying treatment for patients presenting anaphylactic reactions. VIT counts several mechanisms of action, with the increase of IgG1 and IgG4 and a cytokine impairment inducing a Th2-Th1 shift. Pregnancy is a health condition where a Th2 profile is required to prevent fetal rejection, so VIT could be a problem for the fetus when started during pregnancy.

Reducing the sting: Diagnosis and management of Hymenoptera venom allergy

ABSTRACT

Hymenoptera species include stinging insects such as wasps, hornets, bees, and fire ants. Allergic reaction to the venom of these insects is a common presenting complaint for patients in primary care and emergency medicine during warmer months. Patients' clinical presentations may vary, and clinicians must identify the type of reaction to determine treatment and follow-up plans. Treatment of patients allergic to Hymenoptera venom should be individualized based on risk factors, reaction type, and associated comorbidities. This article reviews common features of clinical presentation, diagnosis, and the current mainstays in management of Hymenoptera venom allergy.

Prevalence of mastocytosis and hymenoptera venom allergy in the United States

BACKGROUND

Mastocytosis is a risk factor for hymenoptera venom anaphylaxis (HVA). Current guidelines recommend measuring tryptase in patients with HVA and that those with mastocytosis pursue lifelong venom immunotherapy (VIT). Available data on HVA and mastocytosis largely derive from European single-center studies, and the prevalence of HVA with and without mastocytosis in the United States is unknown.

OBJECTIVE

We sought to determine the prevalence of HVA and mastocytosis in the United States using an insurance claims database and evaluate the impact of mastocytosis on VIT in patients with HVA in a US cohort.

METHODS

The IBM Watson Database, consisting of insurance claims from approximately 27 million US patients in 2018, was queried to identify patients with HVA and/or mastocytosis. Furthermore, a retrospective study of 161 patients undergoing VIT between 2015 and 2018 at the University of Michigan was conducted.

RESULTS

In the IBM Watson Database, the prevalence of HVA was 167 per 100,000 (0.167%) and the prevalence of mastocytosis 10 per 100,000 (0.010%) overall and 97 per 100,000 (0.097%) among those with HVA. Mastocytosis showed a 9.7-fold increase among patients with HVA versus the general population. In the U-M cohort, 2.6% of patients with VIT had mastocytosis. Tryptase level did not correlate with venom reaction severity but was higher in patients with systemic VIT reactions.

CONCLUSIONS

We observed a lower US HVA prevalence than previously reported. Mastocytosis was more common in US patients with HVA, though at lower rates than previously reported. In patients with VIT there was no correlation between tryptase level and reaction severity.

Protease profile of normal and neoplastic mast cells in the human bone marrow with special emphasis on systemic mastocytosis

Mast cells (MC) are immune cells that produce a variety of mediators, such as proteases, that are important in the body's immune responses. MC proteases have pronounced multifunctionality and in many respects determine the biological characteristics of the organ-specific MC population. Although, increased numbers of MC are one of the objective mastocytosis signs, a detailed assessment of the proteases biogenesis and excretion mechanisms in the bone marrow (BM) has not yet been carried out. Here, we performed an analysis of the expression of proteases in patients with various forms of systemic mastocytosis. We presented data on intracellular protease co-localization in human BM MCs and discussed their implication in secretory pathways of MCs in the development of the disease. Systemic mastocytosis, depending on the course, is featured by the formation of definite profiles of specific proteases in various forms of atypical mast cells. Intragranular accumulation of tryptase, chymase and carboxypeptidases in the hypochromic phenotype of atypical mast cells is characterized. Characterization of MC proteases expression during mastocytosis can be used to refine the MC classification, help in a prognosis, and increase the effectiveness of targeted therapy.