Development of a new, more sensitive immunoassay for human tryptase: use in systemic anaphylaxis

Short-term biological variation of serum tryptase

OBJECTIVES

Serum tryptase is a biomarker of mast cell activation. Among others, it is used in the diagnosis of anaphylaxis where a significant increase during the acute phase supports the diagnosis. When evaluating changes in biomarker levels, it is of utmost importance to consider the biological variation of the marker. Therefore, the aim of this study was to evaluate the short-term biological variation of serum tryptase.

METHODS

Blood samples were drawn at 9 AM three days in a row from apparently healthy subjects. On day two, additional blood samples were drawn every third hour for 12 h. The tryptase concentration was measured in serum using a fluoroenzyme immunoassay (ImmunoCAP™, Thermo Fisher Scientific). Linear mixed-effects models were used to calculate components of biological variation.

RESULTS

In 32 subjects, the overall mean concentration of tryptase was 4.0 ng/mL (range, 1.3-8.0 ng/mL). The within-subject variation was 3.7 % (95 % confidence interval (CI) 3.0-4.4 %), the between-subject variation was 31.5 % (95 % CI 23.1-39.8 %), and the analytical variation was 3.4 % (95 % CI 2.9-4.1 %). The reference change value was 13.3 % for an increase in tryptase at a 95 % level of significance. No significant day-to-day variation was observed (p=0.77), while a minute decrease in the serum concentration was observed during the day (p<0.0001).

CONCLUSIONS

Serum tryptase is a tightly regulated biomarker with very low within-subject variation, no significant day-to-day variation, and only minor semidiurnal variation. In contrast, a considerable between-subject variation exists. This establishes serum tryptase as a well-suited biomarker for monitoring.

Gastrointestinal reflux contributes to laryngopharyngeal symptoms that mimic anaphylaxis: COVID-19 vaccination experience

Background

The sensation of throat closure after vaccination is concerning for anaphylaxis and leads to vaccine hesitancy.

Objectives

We characterized patients who developed laryngopharyngeal symptoms (LPhS) after coronavirus disease 2019 (COVID-19) vaccination and assessed risk factors for these symptoms.

Methods

The study analyzed data from the COVID-19 vaccines adverse reactions registry (December 14, 2020, to June 13, 2022). Outcomes included the incidence of postvaccination LPhS and use of epinephrine. We identified and compared risk factors for COVID-19 postvaccination reactions between subjects with and without LPhS.

Results

A total of 158 subjects were enrolled onto the registry. LPhS were reported in 61 subjects (38.6%), of whom 52 (85.2%) received a subsequent dose. With initial vaccination, the use of epinephrine was higher in subjects with LPhS (20%) compared to those without (6%; P = .0094). Fifty-two subjects (85.2%) with LPhS received a subsequent COVID-19 vaccine dose with milder or no symptoms, and none needed treatment with epinephrine. Those with LPhS were more likely to have a history of drug allergies (P = .02), severe medication allergies (P = .03), gastroesophageal reflux disease (P = .018), and need for antireflux medications (P = .0085) compared to controls.

Conclusions

In our registry, postvaccination LPhS were common. LPhS can mimic anaphylaxis and lead to more frequent use of epinephrine. Gastroesophageal reflux disease was more frequent in these subjects. Patients with subjective throat closure sensation can safely receive subsequent vaccine doses with close observation and reassurance. LPhS are not unique to COVID-19 vaccines. Patient and provider education regarding the role of gastroesophageal reflux disease as a risk factor for LPhS with vaccination can improve vaccine uptake.

Using the Right Criteria for MCAS

PURPOSE OF REVIEW

The current article aims to provide a comprehensive update on diagnostic criteria for mast cell activation syndrome (MCAS), addressing challenges in diagnosing and classifying MCAS and its variants.

RECENT FINDINGS

In recent years, there has been a significant increase in our knowledge regarding the underlying mechanisms responsible for the activation of mast cells (MCs) in various pathological conditions. Furthermore, a set of criteria and a classification for MCASs have been established. MCAS is characterized by the presence of typical clinical symptoms, a substantial elevation in serum tryptase levels during an attack compared to the patient's baseline tryptase levels, and a response to MC mediator-targeting therapy. In this report, a thorough examination was conducted on the contemporary literature relating to MCAS, with a focus on comparing the specificity, sensitivity, and robustness of MCAS-related parameters within proposals for diagnosing and classifying MCAS and its variants. Moreover, the significance of employing specific consensus criteria in the assessment and categorization of MCAS in individual patients was underscored, due to the escalating occurrence of patients receiving a misdiagnosis of MCAS based on nonspecific criteria.

Diagnostic Significance of Tryptase for Suspected Mast Cell Disorders

Tryptase has proven to be a very useful and specific marker to demonstrate mast cell activation and degranulation when an acute (i.e., within 4 h after the event) and baseline value (i.e., at least 24 h after the event) are compared and meet the consensus formula (i.e., an increase of 20% + 2). The upper limit of normal determined by the manufacturer is 11.4 ng/mL; however, this boundary has been the subject of debate. According to ECNM and AIM experts, the normal range of baseline tryptase should be 1 to 15 ng/mL. A genetic trait, hereditary alpha tryptasemia, characterized by an increased alpha coding TPSAB1 copy number is associated with a baseline value above 8 ng/mL. Elevated tryptase can also be found in chronic kidney disease, obesity, and hematological neoplasms. A tryptase > 20 ng/mL serves as a minor criterion to diagnose systemic mastocytosis and an increase in tryptase > 20% + 2 during an acute event is a required criterion in the diagnosis of mast cell activation syndrome. The goal of this review is to demonstrate the (in)significance of tryptase using some clinical vignettes and to provide a practical guide on how to manage and interpret an elevated tryptase level.

The Normal Range of Baseline Tryptase Should Be 1 to 15 ng/mL and Covers Healthy Individuals With HαT

Physiological levels of basal serum tryptase vary among healthy individuals, depending on the numbers of mast cells, basal secretion rate, copy numbers of the TPSAB1 gene encoding alpha tryptase, and renal function. Recently, there has been a growing debate about the normal range of tryptase because individuals with the hereditary alpha tryptasemia (HαT) trait may or may not be symptomatic, and if symptomatic, uncertainty exists as to whether this trait directly causes clinical phenotypes or aggravates certain conditions. In fact, most HαT-positive cases are regarded as asymptomatic concerning mast cell activation. To address this point, experts of the European Competence Network on Mastocytosis (ECNM) and the American Initiative in Mast Cell Diseases met at the 2022 Annual ECNM meeting and discussed the physiological tryptase range. Based on this discussion, our faculty concluded that the normal serum tryptase range should be defined in asymptomatic controls, inclusive of individuals with HαT, and based on 2 SDs covering the 95% confidence interval. By applying this definition in a literature screen, the normal basal tryptase in asymptomatic controls (HαT-positive persons included) ranges between 1 and 15 ng/mL. This definition should avoid overinterpretation, unnecessary referrals, and unnecessary anxiety or anticipatory fear of illness in healthy individuals.

Inhibition of KIT for chronic urticaria: a status update on drugs in early clinical development

INTRODUCTION

Chronic urticaria (CU), including chronic spontaneous urticaria (CSU) and chronic inducible urticaria (CIndU), is a prevalent, enduring, mast-cell driven condition that presents challenges in its management. There is a clear need for additional approved treatment options beyond H1 receptor antagonists and the anti-IgE monoclonal antibody (mAb), omalizumab. One of the latest therapeutic strategies targets KIT, which is considered the primary master regulator for mast cell-related disorders.

AREAS COVERED

This review provides a status update on KIT inhibiting drugs in early clinical development for CU.

EXPERT OPINION

Whereas multi-targeted tyrosine kinase KIT inhibitors carry the risk of off-target toxicities, initial data from anti-KIT mAbs indicate significant potential in CSU and CIndU. The prolonged depletion of mast cells over several weeks by barzolvolimab could effectively control urticarial symptoms. Regarding safety, based on theoretical considerations and the available preliminary results, it is already evident that there may be more side effects compared to omalizumab. However, long-term safety data beyond 12 weeks are still lacking. The outcome of ongoing or planned clinical trials with several anti-KIT mAbs will need to demonstrate benefits compared to anti-IgE in CU or whether one approach is better suited for specific urticaria endotypes.

Genetically defined individual reference ranges for tryptase limit unnecessary procedures and unmask myeloid neoplasms

Serum tryptase is a biomarker used to aid in the identification of certain myeloid neoplasms, most notably systemic mastocytosis, where basal serum tryptase (BST) levels >20 ng/mL are a minor criterion for diagnosis. Although clonal myeloid neoplasms are rare, the common cause for elevated BST levels is the genetic trait hereditary α-tryptasemia (HαT) caused by increased germline TPSAB1 copy number. To date, the precise structural variation and mechanism(s) underlying elevated BST in HαT and the general clinical utility of tryptase genotyping, remain undefined. Through cloning, long-read sequencing, and assembling of the human tryptase locus from an individual with HαT, and validating our findings in vitro and in silico, we demonstrate that BST elevations arise from overexpression of replicated TPSAB1 loci encoding canonical α-tryptase protein owing to coinheritance of a linked overactive promoter element. Modeling BST levels based on TPSAB1 replication number, we generate new individualized clinical reference values for the upper limit of normal. Using this personalized laboratory medicine approach, we demonstrate the clinical utility of tryptase genotyping, finding that in the absence of HαT, BST levels >11.4 ng/mL frequently identify indolent clonal mast cell disease. Moreover, substantial BST elevations (eg, >100 ng/mL), which would ordinarily prompt bone marrow biopsy, can result from TPSAB1 replications alone and thus be within normal limits for certain individuals with HαT.

A quarter of a century fundamental and translational research in perioperative hypersensitivity and anaphylaxis at the Antwerp university hospital, a Belgian Centre of Excellence of the World Allergy Organization

Perioperative hypersensitivity constitutes an important health issue, with potential dramatic consequences of diagnostic mistakes. However, safe and correct diagnosis is not always straightforward, mainly because of the application of incorrect nomenclature, absence of easy accessible in-vitro/ex-vivo tests and uncertainties associated with the non-irritating skin test concentrations. In this editorial we summarize the time line, seminal findings, and major realizations of 25 years of research on the mechanisms, diagnosis, and management of perioperative hypersensitivity.

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.

Allergy, inflammation, hepatopathy and coagulation biomarkers in dogs with suspected anaphylaxis due to insect envenomation

Objectives

To compare concentrations of biomarkers of; allergy [mast cell tryptase (MCT) and histamine], inflammation [interleukin (IL)-6,-10, and-18, CXCL8, CCL2, keratinocyte chemoattractant (KC), C-reactive protein (CRP)], endothelial glycocalyx shedding (hyaluronan), coagulation [prothrombin time, activated partial thromboplastin time, fibrinogen concentration, and von Willebrand Factor antigen, protein C (PC) and antithrombin (AT) activity], and hepatopathy [alanine transaminase (ALT), aspartate transaminase (AST), alkaline phosphatase (ALP), and total bilirubin] between dogs with anaphylaxis after suspected insect exposure, dogs with critical illness, and healthy dogs.

Design

This was a single center prospective clinical observational comparative biomarker study that included 25 dogs with anaphylaxis (evidence of insect exposure, acute dermatological signs, and other organ involvement), 30 dogs with other critical illness, and 20 healthy dogs. Differences across groups in biomarker concentrations were tested using one-way ANOVA or Kruskal-Wallis test, with significant P values (<0.05) reported for pairwise differences detected by post-hoc tests. Logistic regression models were used to calculate the area under the receiver operator characteristic curve (AUROC) for discrimination between anaphylaxis and non-anaphylactic illness.

Results

Histamine concentration was significantly higher in the anaphylaxis group than the healthy (P < 0.001) and critically ill groups (P < 0.001), whereas no differences in MCT were detected amongst groups. Biomarker concentrations that were increased relative to healthy dogs in both the anaphylaxis and critically ill groups included IL-10 (P < 0.001 and P = 0.007, respectively), CCL2 (P = 0.007 and P < 0.001, respectively) and AST (both P < 0.001), whereas only the critically ill group had significantly increased CRP (P < 0.001), IL-6 (P < 0.001), KC (P < 0.001), ALP (P < 0.001), and fibrinogen (P = 0.016) concentrations, compared to the healthy group. Only dogs with anaphylaxis had significantly higher hyaluronan (P = 0.021) and ALT (P = 0.021) concentrations, and lower PC (P = 0.030) and AT (P = 0.032) activities, compared to healthy dogs. Both CRP and histamine concentration showed good discrimination between anaphylaxis and other critical illness, with an AUROC of 0.96 (95% CI 0.91-1) and 0.81 (95% CI 0.69-0.93), respectively.

Conclusions

This preliminary study in dogs with anaphylaxis after suspected insect exposure, found evidence of an early innate immune response, glycocalyx shedding and anticoagulant consumption. Both CRP and histamine showed potential clinical utility for differentiation between anaphylaxis and other critical illness.

Estimating the within‐subject (CV I ) and between‐subject (CV G ) biological variation of serum tryptase

Background

Methods

Results

Conclusions

Selected recent advances in understanding the role of human mast cells in health and disease

Mast cells are highly granular tissue-resident cells and key drivers of inflammation, particularly in allergies as well as in other inflammatory diseases. Most mast cell research was initially conducted in rodents but has increasingly shifted to the human system, with the advancement of research technologies and methodologies. Today we can analyze primary human cells including rare subpopulations, we can produce and maintain mast cells isolated from human tissues, and there are several human mast cell lines. These tools have substantially facilitated our understanding of their role and function in different organs in both health and disease. We can now define more clearly where human mast cells originate from, how they develop, which mediators they store, produce de novo, and release, how they are activated and by which receptors, and which neighbouring cells they interact with and by which mechanisms. Considerable progress has also been made regarding the potential contribution of mast cells to disease, which, in turn, has led to the development of novel approaches for preventing key pathogenic effects of mast cells, heralding the era of mast cell-targeted therapeutics. In this review, we present and discuss a selection of some of the most significant advancements and remaining gaps in our understanding of human mast cells during the last 25 years, with a focus on clinical relevance.

Mediator production and severity of aspirin-induced respiratory reactions: Impact of sampling site and body mass index

BACKGROUND

Patients with aspirin-exacerbated respiratory disease can experience severe reactions during aspirin challenge that are associated with high levels of mast cell mediators. The tissue source and clinical factors contributing to systemic mediator levels are unknown.

OBJECTIVE

To determine the concordance between respiratory tract and systemic inflammatory mediator levels and identify clinical factors associated with these mediators.

METHODS

We performed an oral aspirin challenge in 30 subjects with aspirin-exacerbated respiratory disease. Respiratory symptoms and function, nasal mucosal fluid, blood, and urine were collected at baseline, at the onset of a respiratory reaction and over a 3-hour observation period. Changes in nasal and systemic mediator levels were compared.

RESULTS

Neither tryptase nor leukotriene E₄ levels in nasal fluid correlated with serum tryptase or urinary leukotriene E₄ at baseline or during reactions. We observed no association between the baseline or aspirin-induced change in nasal versus urinary leukotriene E₄ and serum tryptase levels. Body mass index inversely correlated with baseline and aspirin-induced urinary leukotriene E₄, prostaglandin D₂ metabolite, and serum tryptase levels, as well as with aspirin-induced symptoms and respiratory function, but not with nasal mediators.

CONCLUSION

The levels of nasal and systemic aspirin-induced mast cell products are discordant in aspirin-exacerbated respiratory disease. Systemically detected levels are likely derived from mast cells outside of the sinonasal cavity and do not accurately reflect upper respiratory tract production. Increased body mass index decreases systemic mast cell mediator production and reaction severity, supporting a contribution of metabolic regulation in aspirin-induced systemic reactions.

Selecting the Right Criteria and Proper Classification to Diagnose Mast Cell Activation Syndromes: A Critical Review

In recent years, knowledge about mechanisms underlying mast cell activation (MCA) and accumulation in various pathologic conditions increased substantially. In addition, criteria and a classification of MCA syndromes (MCASs) have been set forth. MCAS is defined by typical clinical symptoms, a substantial increase in serum tryptase level during an attack over the patient's baseline tryptase, and a response of the symptoms to drugs targeting mast cells, mediator production, and/or mediator effects. Alternative diagnostic criteria of MCAS have also been suggested, but these alternative criteria often lack specificity and validation. In this report, we critically review the contemporary literature relating to MCAS and compare the specificity, sensitivity, and strength of MCAS-related parameters within proposals to diagnose and classify MCAS and its variants. Furthermore, we highlight the need to apply specific consensus criteria in the evaluation and classification of MCAS in individual patients. This is an urgent and important medical necessity because as an increasing number of patients are being given a misdiagnosis of MCAS based on nonspecific criteria, which contributes to confusion and frustration by patients and caregivers and sometimes may delay recognition and treatment of correct medical conditions that often turn out to be unrelated to MCA.

Mast Cell Activation During Suspected Perioperative Hypersensitivity: A Need for Paired Samples Analysis

BACKGROUND

Perioperative hypersensitivity (POH) reactions constitute a significant clinical and diagnostic challenge. A transient increase in serum tryptase during POH reflects mast cell activation (MCA) and helps to recognize an underlying hypersensitivity mechanism.

OBJECTIVE

To determine the diagnostic performance of different tryptase decision thresholds based on single and paired measurements to document MCA in suspected POH.

METHODS

Acute serum tryptase (aST) and baseline serum tryptase (bST) samples were obtained from patients referred to our outpatients clinic because of clinical POH. Tryptase samples from controls were obtained before induction (Tt₀) and 1.5 hours after induction (Tt₁) in uneventful anesthesia. Different cutoff points for tryptase increase over bST and the percentage increase in tryptase (%T) were calculated and compared with existing thresholds: aST > [1.2 × (bST) + 2] (consensus formula), aST higher than 11.4 ng/mL, and aST higher than 14 ng/mL.

RESULTS

Patients with POH had higher bST and aST levels compared with controls (respectively 5.15 vs 2.28 ng/mL for bST and 20.30 vs 1.92 ng/mL for aST). The consensus formula and a tryptase increase over bST of greater than or equal to 3.2 ng/mL held the highest accuracies to document MCA in POH (respectively 81% and 82%). A bST of higher than 8 ng/mL was present in 4% of controls, 5% of patients with grade 1 POH, 24% of patients with grade 2 POH, 15% of patients with grade 3 POH, and 17% of patients with grade 4 POH.

CONCLUSIONS

Our data endorse the consensus formula for detection of MCA in POH. Furthermore, it shows that a bST of higher than 8 ng/mL was associated with occurrence of anaphylaxis.

Fatal anaphylaxis due to alpha-gal syndrome after initial cetuximab administration: The first forensic case report

Cetuximab is mainly used for the treatment of advanced and metastatic colorectal cancer. Owing to the oligosaccharide galactose-α-1,3-galactose (α-gal) in its heavy chain, cetuximab can induce severe IgE-dependent anaphylaxis. α-Gal is also the antigen responsible for α-gal syndrome, known as mammalian meat allergy. Patients with α-gal syndrome may suffer from cetuximab-induced anaphylaxis at the first administration because of developed α-gal-specific IgE antibodies. A male patient in his 50 s with metastatic colon cancer was receiving chemotherapy involving scheduled cetuximab administration. However, he died soon after the first administration. Forensic autopsy confirmed rectal cancer, metastatic rectal cancer in the liver, and renal cancer. Laboratory blood tests revealed the presence of cetuximab- and beef-specific IgE antibodies before cetuximab administration and an extremely high level of tryptase after administration. Thus, we determined that the death was caused by cetuximab-induced anaphylaxis due to the preexisting α-gal syndrome. To the best of our knowledge, this is the first autopsy case report in forensic medicine of fatal anaphylaxis after initial cetuximab administration.

Use and Interpretation of Acute and Baseline Tryptase in Perioperative Hypersensitivity and Anaphylaxis

Paired acute and baseline serum or plasma tryptase sampling and determination have recently been included as a mechanistic approach in the diagnostic and management guidelines of perioperative immediate hypersensitivity and anaphylaxis. The timing of this paired sampling is clearly defined in international consensus statements, with the optimal window for acute tryptase sampling between 30 minutes and 2 hours after the initiation of symptoms, whereas baseline tryptase should be measured in a sample collected before the event (preop) or at least 24 hours after all signs and symptoms have resolved. A transient elevation of the acute tryptase level greater than [2 + (1.2 × baseline tryptase level)] supports the involvement and activation of mast cells. Here, we provide the clinical, pathophysiological, and technical rationale for the procedure and interpretation of paired acute and baseline tryptase. Clinical examples, up-to-date knowledge of hereditary α-tryptasemia as a frequent cause of baseline tryptase of 7 μg/L and higher, mastocytosis, other clonal myeloid disorders, cardiovascular or renal failure, and technical improvements resulting in continued lowering of the 95th percentile value are discussed. Clues for improved management of perioperative immediate hypersensitivity and anaphylaxis include (1) sustained dissemination and implementation of updated guidelines; (2) preoperative sample storage for deferred analysis; (3) referral for thorough allergy investigation, screening for mast cell-related disorders, and recommendations for future anesthetic procedures; and (4) sustained collaboration between anesthesiologists, immunologists, and allergists.

Histamine, mast cell tryptase and post-exercise hypotension in healthy and collapsed marathon runners

PURPOSE

Heat stress exacerbates post-exercise hypotension (PEH) and cardiovascular disturbances from elevated body temperature may contribute to exertion-related incapacity. Mast cell degranulation and muscle mass are possible modifiers, though these hypotheses lack practical evidence. This study had three aims: (1) to characterise pre-post-responses in histamine and mast cell tryptase (MCT), (2) to investigate relationships between whole body muscle mass (WBMM) and changes in blood pressure post-marathon, (3) to identify any differences in incapacitated runners.

METHODS

24 recreational runners were recruited and successfully completed the 2019 Brighton Marathon (COMPLETION). WBMM was measured at baseline. A further eight participants were recruited from incapacitated runners (COLLAPSE). Histamine, MCT, blood pressure, heart rate, body temperature and echocardiographic measures were taken before and after exercise (COMPLETION) and upon incapacitation (COLLAPSE).

RESULTS

In completion, MCT increased by nearly 50% from baseline (p = 0.0049), whereas histamine and body temperature did not vary (p > 0.946). Systolic (SBP), diastolic (DBP) and mean (MAP) arterial blood pressures and systemic vascular resistance (SVR) declined (p < 0.019). WBMM negatively correlated with Δ SBP (r = - 0.43, p = 0.046). For collapse versus completion, there were significant elevations in MCT (1.77 ± 0.25 μg/L vs 1.18 ± 0.43 μg/L, p = 0.001) and body temperature (39.8 ± 1.3 °C vs 36.2 ± 0.8 °C, p < 0.0001) with a non-significant rise in histamine (9.6 ± 17.9 μg/L vs 13.7 ± 33.9 μg/L, p = 0.107) and significantly lower MAP, DBP and SVR (p < 0.033).

CONCLUSION

These data support the hypothesis that mast cell degranulation is a vasodilatory mechanism underlying PEH and exercise associated collapse. The magnitude of PEH is inversely proportional to the muscle mass and enhanced by concomitant body heating.

IRRITABLE BOWEL SYNDROME AND BASAL SERUM TRYPTASE: THE CORRELATION BETWEEN SUBTYPE, SEVERITY AND COMORBIDITIES. A PILOT STUDY

INTRODUCTION

Activation of mast cells causes alteration in epithelial and neuromuscular function, and is involved in visceral hypersensitivity and dysmotility in gastrointestinal functional disorders.

OBJECTIVES

Primary: Evaluate differences in basal serum tryptase (BST) between patients with irritable bowel syndrome (IBS) and healthy controls. Secondary: BST depending on IBS subtype (diarrhea: IBS-D; constipation: IBS-C), comorbidities and correlations with IBS severity and quality of life.

MATERIAL AND METHODS

Prospective control-case study in IBS patients (Rome IV criteria). BST was determined (ImmunoCAP-Phadia, Sweden®) IBS Severity Score (IBSSS), pain, bloating and flatulence analogue scales, IBS quality of life (IBSQOL) and patient health status (PHQ-9) were performed. BST is the primary variable in achieving the primary end-point.

RESULTS

Thirty-two patients, 21 (65.6%) IBS-D, 11 (34.4%) IBS-C and 32 controls were included. Mean IBSSSS: 326.6 (± 71.4), IBSQOL: 76 (± 20.3) and PHQ9: 10.2 (± 5.9). BST was 4.8 ± 2.6 in IBS and 4.7± 2.6 in controls (p=0.875). There was no difference in BST between IBS subtypes (4.7 ± 2.9 in IBS-D and 5± 1.8 in IBS-C; p =0.315) or IBS severity (p=0.662). However, BST was higher in patients with IBS and extraintestinal comorbidities compared to other patients and controls (p=0.029). This subgroup also has more severe bloating (p=0.021). There was no correlation between BST, quality of life (p=0.9260) and health status (p=0.3985).

CONCLUSION

BST does not discriminate between IBS patients and controls. However, BST was higher in patients with IBS with extraintestinal comorbidities which have more severe bloating. This finding is worthy of investigation.

Hypertryptasemia and Mast Cell-Related Disorders in Severe Osteoporotic Patients

Purpose

Systemic mastocytosis (SM) is characterized by a clonal proliferation of neoplastic mast cells (MCs) in one or more extracutaneous organs including the bone marrow (BM). SM is often associated with osteoporosis (OP) and fractures. Hypertryptasemia usually occurs in SM. We investigated the prevalence of hypertryptasemia in a series of severe osteoporotic patients, the performance of the tryptase test in diagnosing SM in these patients, and their bone features.

Methods

The medical records of 232 patients (168 females and 64 males) with a diagnosis of OP (50.4% with fractures) and a serum tryptase assessment were reviewed. BM assessment was performed in a subset of hypertryptasemic patients; clinical, biochemical, and radiographic data were collected.

Results

Hypertryptasemia was detected in 33 patients. BM assessment (n = 16) was normal in 8 hypertryptasemic patients, while BM criteria for the diagnosis of SM were met in 3 patients, MC alterations were detected in 4 patients, and one patient presented a polycythemia vera. Serum tryptase levels were higher than 11.4 ng/ml in all patients with BM alterations. The best cut-off of tryptase level related to BM alterations was 17.9 ng/ml, with a sensibility and sensitivity of 75% (AUC = 0.797 and P = 0.015 by ROC analysis). All osteoporotic patients with hypertryptasemia experienced at least one vertebral fracture associated with a severe reduction of the lumbar bone mineral density.

Conclusions

The prevalence of MC-related disorders in severe OP was 3.0%, accounting for the 7.4% of the secondary causes of OP. MC-related disorders may be involved in bone fragility and assessment of serum tryptase is useful to detect MC-related disorders.

Unique Effect of Aspirin Therapy on Biomarkers in Aspirin-exacerbated Respiratory Disease. A Prospective Trial

Rationale: Daily high-dose aspirin therapy benefits many patients with aspirin-exacerbated respiratory disease but provides no benefit for aspirin-tolerant patients with asthma. Type 2 inflammation characterizes aspirin-exacerbated respiratory disease.Objectives: To determine whether high-dose aspirin therapy changes biomarkers of type 2 inflammation in aspirin-exacerbated respiratory disease.Methods: Forty-two subjects with aspirin-exacerbated respiratory disease underwent an aspirin desensitization and were placed on high-dose aspirin (1,300 mg daily). Fifteen aspirin-tolerant subjects with asthma were also placed on high-dose aspirin. Biologic specimens and clinical parameters were collected at baseline and after 8 weeks on aspirin. Urinary eicosanoids, plasma tryptase and cytokine levels, platelet-leukocyte aggregates, and granulocyte transcripts were assessed.Measurements and Main Results: Eight weeks of high-dose aspirin decreased nasal symptoms and urinary prostaglandin E metabolite (P < 0.05) and increased urinary leukotriene E4 (P < 0.01) levels in subjects with aspirin-exacerbated respiratory disease, but not in those with aspirin-tolerant asthma. Urinary prostaglandin D2 and thromboxane metabolites decreased in both groups. Only in subjects with aspirin-exacerbated respiratory disease, exhaled nitric oxide (P < 0.05), plasma tryptase (P < 0.01), and blood eosinophil (P < 0.01) and basophil (P < 0.01) counts increased and plasma tryptase correlated with eosinophil counts (Pearson r = 0.514; P < 0.01) on aspirin. After correction for eosinophil counts, aspirin-induced changes in blood granulocyte transcripts did not differ between groups. Aspirin had no effect on platelet-leukocyte aggregates, platelet activation markers, or plasma cytokines in either group.Conclusions: High-dose aspirin therapy for 8 weeks paradoxically increases markers of type 2 inflammation in subjects with aspirin-exacerbated respiratory disease, despite reducing nasal symptoms. This effect of aspirin is unique to aspirin-exacerbated respiratory disease and not observed in subjects with aspirin-tolerant asthma.

Improvement of the Elevated Tryptase Criterion to Discriminate IgE- From Non-IgE-Mediated Allergic Reactions

BACKGROUND

Differentiating between immunoglobulin E (IgE)-dependent and IgE-independent hypersensitivity reactions may improve the etiologic orientation and clinical management of patients with allergic reactions in the anesthesia setting. Serum tryptase levels may be useful to discriminate the immune mechanism of allergic reactions, but the diagnostic accuracy and optimal cutpoint remain unclear.We aimed to compare the diagnostic accuracy of tryptase during reaction (TDR) alone and the TDR/basal tryptase (TDR/BT) ratio for discriminating IgE- from non-IgE-mediated allergic reactions, and to estimate the best cut point for these indicators.

METHODS

We included 111 patients (45% men; aged 3-99 years) who had experienced an allergic reaction, even though the allergic reaction could be nonanaphylactic. Allergy tests were performed to classify the reaction as an IgE- or non-IgE-mediated one. The area under the curve (AUC) of the receiver operating characteristic analysis was performed to estimate the discriminative ability of TDR and TDR/BT ratio.

RESULTS

An IgE-mediated reaction was diagnosed in 49.5% of patients, and 56% of patients met anaphylaxis criteria. The median (quartiles) TDR for the IgE-mediated reactions was 8.0 (4.9-19.6) and 5.1 (3.5-8.1) for the non-IgE-mediated (P = .022). The median (quartiles) TDR/BT ratio was 2.7 (1.7-4.5) in IgE-mediated and 1.1 (1.0-1.6) in non-IgE-mediated reactions (P < .001). The TDR/BT ratio showed the greatest ability to discriminate IgE- from non-IgE-mediated reactions compared to TDR (AUC TDR/BT = 0.79 [95% confidence interval (CI), 0.70-0.88] and AUC TDR = 0.66 [95% CI, 0.56-0.76]; P = .001). The optimal cut point for TDR/BT (maximization of the sum of the sensitivity and specificity) was 1.66 (95% CI, 1.1-2.2).

CONCLUSIONS

The TDR/BT ratio showed a significantly better discriminative ability than TDR to discriminate IgE- from non-IgE-mediated allergic reactions. An optimal TDR/BT ratio threshold of approximately 1.66 may be useful in clinical practice to classify allergic reactions as IgE- or non-IgE-mediated.

Paired acute-baseline serum tryptase levels in perioperative anaphylaxis: An observational study

BACKGROUND

Anaphylaxis is recognized mainly through clinical criteria, which may lack specificity or relevance in the perioperative setting. The transient increase in serum tryptase has been proposed since 1989 as a diagnostic tool. Sampling for well-defined acute and baseline determinations has been recommended. We assessed the performance of four proposed algorithms with tightly controlled time frames for tryptase sampling, their robustness with inadequate sampling times, and the possible use of mature tryptase determination.

METHODS

A retrospective study was performed on 102 adult patients from the Aix-Marseille University Hospitals who had experienced a perioperative hypersensitivity reaction clinically suggesting anaphylaxis. EAACI and ICON criteria were used to diagnose anaphylaxis. Mature and total serum tryptase levels were measured.

RESULTS

Based on EAACI guidelines, clinical diagnostic criteria for anaphylaxis were found in 76 patients and lacking in 26. The most effective algorithm was the international consensus recommendation of 2012 that acute total tryptase levels should be greater than ([1.2×baseline tryptase] + 2] μg/L to be considered a clinically significant rise. In our cohort, this algorithm achieved 94% positive predictive value (PPV), 53% negative predictive value (NPV), 75% sensitivity, 86% specificity, and a Youden's index value of 0.61. A detectable acute mature tryptase level showed lower sensitivity, particularly in patients with acute total tryptase levels lower than 16 μg/L. Acute tryptase levels varied as a function of the clinical severity of anaphylaxis.

CONCLUSION

Total tryptase levels in serum discriminated between nonanaphylactic and anaphylactic events in a perioperative setting when acute and baseline levels were collected and analyzed by the consensus algorithm.

Mast cell tryptase - Marker and maker of cardiovascular diseases

Mast cells are tissue-resident cells, which have been proposed to participate in various inflammatory diseases, among them the cardiovascular diseases (CVDs). For mast cells to be able to contribute to an inflammatory process, they need to be activated to exocytose their cytoplasmic secretory granules. The granules contain a vast array of highly bioactive effector molecules, the neutral protease tryptase being the most abundant protein among them. The released tryptase may act locally in the inflamed cardiac or vascular tissue, so contributing directly to the pathogenesis of CVDs. Moreover, a fraction of the released tryptase reaches the systemic circulation, thereby serving as a biomarker of mast cell activation. Actually, increased levels of circulating tryptase have been found to associate with CVDs. Here we review the biological relevance of the circulating tryptase as a biomarker of mast cell activity in CVDs, with special emphasis on the relationship between activation of mast cells in their tissue microenvironments and the pathophysiological pathways of CVDs. Based on the available in vitro and in vivo studies, we highlight the potential molecular mechanisms by which tryptase may contribute to the pathogenesis of CVDs. Finally, the synthetic and natural inhibitors of tryptase are reviewed for their potential utility as therapeutic agents in CVDs.

Dual functionality of β-tryptase protomers as both proteases and cofactors in the active tetramer

Human β-tryptase, a tetrameric trypsin-like serine protease, is an important mediator of the allergic inflammatory responses in asthma. During acute hypersensitivity reactions, mast cells degranulate, releasing active tetramer as a complex with proteoglycans. Extensive efforts have focused on developing therapeutic β-tryptase inhibitors, but its unique activation mechanism is less well-explored. Tryptase is active only after proteolytic removal of the pro-domain followed by tetramer formation via two distinct symmetry-related interfaces. We show that the cleaved I16G mutant cannot tetramerize, likely due to impaired insertion of its N terminus into its "activation pocket," indicating allosteric linkage at multiple sites on each protomer. We engineered cysteines into each of the two distinct interfaces (Y75C for small or I99C for large) to assess the activity of each tetramer and disulfide-locked dimer. Using size-exclusion chromatography and enzymatic assays, we demonstrate that the two large tetramer interfaces regulate enzymatic activity, elucidating the importance of this protein-protein interaction for allosteric regulation. Notably, the I99C large interface dimer is active, even in the absence of heparin. We show that a monomeric β-tryptase mutant (I99C*/Y75A/Y37bA, where C* is cysteinylated Cys-99) cannot form a dimer or tetramer, yet it is active but only in the presence of heparin. Thus heparin both stabilizes the tetramer and allosterically conditions the active site. We hypothesize that each β-tryptase protomer in the tetramer has two distinct roles, acting both as a protease and as a cofactor for its neighboring protomer, to allosterically regulate enzymatic activity, providing a rationale for direct correlation of tetramer stability with proteolytic activity.

A new humanized in vivo model of KIT D816V+ advanced systemic mastocytosis monitored using a secreted luciferase

Systemic mastocytosis are rare neoplasms characterized by accumulation of mast cells in at least one internal organ. The majority of systemic mastocytosis patients carry KIT D816V mutation, which activates constitutively the KIT receptor. Patient with advanced forms of systemic mastocytosis, such as aggressive systemic mastocytosis or mast cell leukemia, are poorly treated to date. Unfortunately, the lack of in vivo models reflecting KIT D816V+ advanced disease hampers pathophysiological studies and preclinical development of new therapies for such patients. Here, we describe a new in vivo model of KIT D816V+ advanced systemic mastocytosis developed by transplantation of the human ROSAKIT D816V-Gluc mast cell line in NOD-SCID IL-2R γ-/- mice, using Gaussia princeps luciferase as a reporter. Intravenous injection of ROSAKIT D816V-Gluc cells led, in 4 weeks, to engraftment in all injected primary recipient mice. Engrafted cells were found at high levels in bone marrow, and at lower levels in spleen, liver and peripheral blood. Disease progression was easily monitored by repeated quantification of Gaussia princeps luciferase activity in peripheral blood. This quantification evidenced a linear relationship between the number of cells injected and the neoplastic mast cell burden in mice. Interestingly, the secondary transplantation of ROSAKIT D816V-Gluc cells increased their engraftment capability. To conclude, this new in vivo model mimics at the best the features of human KIT D816V+ advanced systemic mastocytosis. In addition, it is a unique and convenient tool to study the kinetics of the disease and the potential in vivo activity of new drugs targeting neoplastic mast cells.

Patterns of anaphylaxis after diagnostic workup: A follow-up study of 226 patients with suspected anaphylaxis

BACKGROUND

Most published studies on anaphylaxis are retrospective or register based. Data on subsequent diagnostic workup are sparse. We aimed to characterize patients seen with suspected anaphylaxis at the emergency care setting (ECS), after subsequent diagnostic workup at our Allergy Center (AC).

METHODS

Prospective study including patients from the ECS, Odense University Hospital, during May 2013-April 2014. Possible anaphylaxis cases were daily identified based on a broad search profile including history and symptoms in patient records, diagnostic codes and pharmacological treatments. At the AC, all patients were evaluated according to international guidelines.

RESULTS

Among 226 patients with suspected anaphylaxis, the diagnosis was confirmed in 124 (54.9%) after diagnostic workup; 118 of the 124 fulfilled WAO/EAACI criteria of anaphylaxis at the ECS, while six were found among 46 patients with clinical suspicion but not fulfilling the WAO/EAACI criteria at the ECS. The estimated incidence rate of anaphylaxis was 26 cases per 100 000 person-years and the one-year period prevalence was 0.04%. The most common elicitor was drugs (41.1%) followed by venom (27.4%) and food (20.6%). In 13 patients (10.5%), no elicitor could be identified. Mastocytosis was diagnosed in 7.7% of adult patients and was significantly associated with severe anaphylaxis. Atopic diseases were significantly associated only with food-induced anaphylaxis. Cofactors were present in 58.1% and were significantly associated with severe anaphylaxis.

CONCLUSION

A broad search profile in the ECS and subsequent diagnostic workup is important for identification and classification of patients with anaphylaxis. Evaluation of comorbidities and cofactors is important.

Risk factors in Hymenoptera venom allergy

Abstract. Risk factors should be part of the decision, of which patient should be offered venom immunotherapy (VIT) and how VIT should be performed. Risk factors for a severe systemic anaphylactic reaction (SAR) after a Hymenoptera field sting include a preceding less severe sting reaction, a wasp sting, an increased baseline serum tryptase concentration (BSTC), mastocytosis, older age, ACE inhibitor medication, and male gender. During VIT, treatment with honey bee venom is the most important risk factor for a SAR. Further risk factors include a high BSTC (for vespid VIT only), presence of venom specific IgE in serum, any antihypertensive medication during therapy, and an ultra-rush protocol for build-up. Treatment failure is more common in patients suffering from honey bee venom allergy, high BSTC (for vespid VIT only) or mastocytosis, and in those who had experienced side effects during VIT. Besides discontinuing antihypertensive medication or switching to a moderate type of dose increase during build-up, little can be done to minimize the risks associated with VIT. Increasing the maintenance dose may improve the efficacy of VIT. In patients with a particularly high risk for treatment failure, or in case of treatment failure, VIT should include an increased maintenance dose right from the beginning. Usually, 200 µg will be sufficient.

Continuous diphenhydramine infusion and imatinib for KIT-D816V-negative mast cell activation syndrome: a case report

Background

We present the first full case report of the treatment of mast cell activation syndrome with continuous diphenhydramine infusion, which resulted in the improvement of anaphylactic reactions and a decrease in hospital readmission. Furthermore, the patient received imatinib in the absence of the KIT-D816V mutation, which led to further improvement of quality of life. Currently, we are trying to wean this patient off diphenhydramine; if successful, this attempt will represent the first reported case.

Case presentation

An 18-year-old white girl presented with a flare of mast cell activation syndrome and received epinephrine and steroids. She had failed multiple previous therapies, and her quality of life was affected due to two to three flares/week. She was started on continuous diphenhydramine infusion and imatinib, which led to a decrease in hospital admissions and marked improvement in her quality of life.

Conclusions

Continuous diphenhydramine infusion can provide promising outcomes following the failure of intermittent antihistamine dosing in patients with severe mast cell activation syndrome. Initiating continuous diphenhydramine infusion may be helpful in an intensive care setting when the patient is particularly prone to anaphylaxis and/or the resources needed to manage anaphylaxis are not available outside the intensive care unit. Furthermore, imatinib provides benefits in KIT-D816V-negative mast cell disorders due to other unknown mutations.

In Vitro Research Tools in the Field of Human Immediate Drug Hypersensitivity and Their Present Use in Small Animal Veterinary Medicine

Drug hypersensitivity reactions (DHR) are immune-mediated idiosyncratic adverse drug events. Type I DHR are often referred to as "immediate" and involve B lymphocyte-secreted IgE that bind to the membrane of basophils and mast cells, inducing their degranulation. This review presents various in vitro tests that were developed in the field of human type I HS and implemented as clinical diagnostic tools in human cases of immediate DHR. The respective strengths and weaknesses of each test will be discussed in parallel of validation data such as specificity and sensitivity whenever available. Some of them have also been used as diagnostic tools in veterinary medicine, but not in cases of immediate DHR. Most of these diagnostic tools can be categorized into humoral and cellular tests. The former tests measure serum concentrations of factors, such as histamine, tryptase, and drug-specific IgE. The latter assays quantify markers of drug-induced basophil activation or drug-specific lymphocyte proliferation. Pharmacogenetic markers have also been investigated in immediate DHR, but not as extensively as in non-immediate ones. Throughout, practical aspects and limitations of the tests, as well as sensitivity and specificity parameters, will be presented. In addition, the experience of veterinary medicine with these diagnostic tools will be summarized. However, to date, none of them has ever been reported in a veterinary case of type I DHR.

How to interpret mast cell tests

Mast cell tryptase (tryptase) is an enzyme produced almost exclusively by mast cells that is easy to measure using a widely available test. In this article we discuss the physiology of the mast cell and how that relates to IgE-mediated anaphylaxis and mastocytosis. We also describe the technical aspects of testing tryptase and the reported normal ranges in health. Finally we explore the diagnostic performance of serum mast cell tryptase measurements, when used to confirm anaphylaxis, estimate future anaphylaxis risk and in diagnosing/monitoring leukaemia.

Incidence of infusion reactions to anti-neoplastic agents in early phase clinical trials: The MD Anderson Cancer Center experience

Infusion reactions (IRs) to anti-neoplastic agents require prompt recognition and immediate treatment to avert significant complications. We conducted a retrospective review of the medical records of consecutive patients who received anti-neoplastic therapy in the outpatient treatment center of the Department of Investigational Cancer Therapeutics from January 1, 2013 to November 30, 2013. Of the 597 patients who received treatment, 9 (1.5 %) had IRs (all ≤ grade 2). The most common IRs observed on first occurrence were chills (n = 5), itching, rash, and facial flushing (n = 3 each). There were no IR-related deaths. All the IRs were reversible with appropriate symptomatic treatment and the therapy was completed after temporary cessation of infusion in 7 of the 9 patients. The infusion was stopped in 2 patients due to symptoms suggestive of IgE-mediated allergic reaction and cytokine storm. Five of the 8 patients who were re-challenged with the same therapy developed a similar reaction. However, the infusion was completed in 4 of the 5 patients after administration of intravenous diphenhydramine and/or hydrocortisone, or slowing the rate of infusion. And, subsequent cycles with the same agents were uneventful. IRs to anti-neoplastic agents are rare. Though the clinical presentations are overlapping, most IRs are not IgE-mediated allergic reactions. Appropriate premedication and slow rate of infusion facilitates uneventful administration of the anti-neoplastic agents in subsequent cycles. Further study in a larger cohort of patients to identify biomarkers of hypersensitivity is warranted.

A novel combination of an IgE mediated adult onset food allergy and a suspected mast cell activation syndrome presenting as anaphylaxis

BACKGROUND

Adult onset food allergy is a rare, but increasingly recognized phenomenon. Mast cell activation syndromes present an ongoing diagnostic and classification challenge. The combination of the two has been rarely described in the literature.

CASE PRESENTATION

We present a case of a new onset, IgE mediated food allergy in combination with a mast cell activation syndrome in an elderly patient not known to have a history of atopy. He presented to a hospital with a first presentation of anaphylaxis manifesting profound hypotension following consumption of a stew consisting of fish and shellfish. He had a persistently elevated serum tryptase and demonstrated evidence of high titre serum specific IgE to shellfish. He responded well to histaminergic blockade.

CONCLUSIONS

Given that mast cell activation syndromes pose an increased risk for recurrent, severe anaphylaxis and that secondary causes of mast cell activation syndromes are more prevalent with aging, this case highlights the importance of considering this entity when evaluating an elderly patient with a first presentation of anaphylaxis.

Management and Prevention of Anaphylaxis

Anaphylaxis prevalence has increased within the last few years. This may be due to a marked increase in allergic sensitization to foods especially in the pediatric population, as well as to an increase in outdoor recreational habits and the availability of new biologic medications.  Furthermore, guidelines for the diagnosis of anaphylaxis have been published, thus facilitating the recognition of this disorder. Diagnosis of anaphylaxis is mainly based on history and clinical criteria of organ system involvement. The serum tryptase assay is now commercially available and may be a helpful diagnostic tool in certain clinical situations involving hypotension, but not in the context of food-induced anaphylaxis. Treatment of anaphylaxis mainly involves the use of epinephrine as a first line medication for severe manifestations followed by  symptomatic management of specific  symptoms, such as antihistamines for urticaria and albuterol for wheezing. Although commonly practiced, treatment with systemic corticosteroids  is not supported by evidence-based literature. Observation in a medical facility for 4-6 hours is recommended to monitor for late phase reactions, although these rarely occur. Education is an essential component of management of a patient with a previous history of anaphylaxis, emphasizing early use of epinephrine and providing a written action plan. Referral to a board-certified allergist/immunologist is recommended to determine  the cause of the anaphylaxis as well as to rule out other potential conditions. In this review, our main focus will be on the treatment and prevention of anaphylaxis while providing our readers with a brief introduction to the diagnosis of anaphylaxis, its prevalence and its most common causes.

Update on Mastocytosis (Part 1): Pathophysiology, Clinical Features, and Diagnosis

Mastocytosis is a term used to describe a heterogeneous group of disorders characterized by clonal proliferation of mast cells in various organs. The organ most often affected is the skin. Mastocytosis is a relatively rare disorder that affects both sexes equally. It can occur at any age, although it tends to appear in the first decade of life, or later, between the second and fifth decades. Our understanding of the pathophysiology of mastocytosis has improved greatly in recent years, with the discovery that somatic c-kit mutations and aberrant immunophenotypic features have an important role. The clinical manifestations of mastocytosis are diverse, and skin lesions are the key to diagnosis in most patients.

The serum tryptase test: an emerging robust biomarker in clinical hematology

During the past few years, a number of molecular markers have been developed in clinical hematology, most of them related to specific gene defects. However, there is also an unmet need to develop novel serologic parameters to improve diagnostics and prognostication in daily practice. Among these, the serum tryptase appears to be a most reliable biomarker of myeloid neoplasms. Elevated tryptase levels are found in subgroups of patients with mastocytosis, myelodysplastic syndrome, myeloproliferative neoplasm, acute myeloid leukemia, chronic myeloid leukemia and chronic eosinophilic leukemia. In these patients, the tryptase level is of diagnostic and/or prognostic significance. In mastocytosis, an elevated tryptase level is a minor criterion of systemic disease and in BCR-ABL1(+) chronic myeloid leukemia, elevated tryptase at diagnosis correlates with treatment responses and overall survival. In patients with elevated tryptase, the enzyme also serves as follow-up parameter and can be employed to measure treatment-responses. In the current article, we review and update the perspectives of tryptase and provide recommendations for use of this conventional biomarker in daily practice.

Diagnostic value of histamine and tryptase concentrations in severe anaphylaxis with shock or cardiac arrest during anesthesia

BACKGROUND

The diagnosis of acute life-threatening allergic reactions during anesthesia relies on clinical signs, histamine and/or tryptase measurements, and allergic testing. In patients who die after the reaction, skin tests cannot be performed, and the effect of resuscitation manoeuvres on mediator concentrations is unknown. The authors compared plasma histamine and tryptase concentrations in patients with severe allergic reactions during anesthesia with those measured in patients with shock due to other causes.

METHODS

Patients with life-threatening allergic reactions were retrieved from a previous database (Group ALLERGY). All had positive allergy tests to administered agents. Patients with severe septic/cardiogenic shock or cardiac arrest (Group CONTROL) had histamine and tryptase measurements during resuscitation manoeuvres. Receiver operating characteristics curves were built to calculate the optimal mediator thresholds differentiating allergic reactions from others.

RESULTS

One hundred patients were included, 75 in Group ALLERGY (cardiovascular collapse, 67; cardiac arrest, 8) and 25 in Group CONTROL (shock, 11; cardiac arrest, 14). Mean histamine and tryptase concentrations remained unchanged throughout resuscitation in Group CONTROL and were significantly higher in Group ALLERGY. The optimal thresholds indicating an allergic mechanism were determined as 6.35 nmol/l for histamine (sensitivity: 90.7% [95% CI, 81.7 to 96.1]; specificity: 91.7% [73.0 to 98.9]) and 7.35 μg/l for tryptase (sensitivity: 92% [83.4 to 97.0]; specificity: 92% [73.9 to 99.0]).

CONCLUSIONS

Resuscitation manoeuvres by themselves did not modify mediator concentrations. Virtually all life-threatening reactions during anesthesia associated with mediator concentrations exceeding the thresholds were allergic events. These findings have potential forensic interest when a patient dies during anesthesia.

Serum Concentrations of Tryptase in Children

Background: Mast cells are dispersed in many tissues, especially in digestive and respiratory-tract mucosal membranes. Tryptase, considered a marker of mast-cell activity, is the most important protease released from these cells during degranulation. Tryptase concentration is mainly accessed in anaphylaxis and mastocytosis, being one diagnostic criteria of this disease. There are no data concerning tryptase activity in healthy children in the current literature. Aim: The aims of this study were the analysis of concentrations of serum tryptase in healthy children, and determining reference values of the enzyme at different developmental ages. Materials and methods: The investigated group consisted of 131 healthy children (75 girls, 56 boys) aged 3 months-18 years. The concentration of tryptase in the studied samples was evaluated by the fluoro-immuno-enzymatic method with UniCAP. Results: The mean concentration of serum tryptase in the studied group was 2.8±2.2 ng/dL: 2.5±2.2 ng/dL in girls and 3.2±2.1 ng/dL in boys. Conclusion: The upper reference limit of 7.2 ng/dL was lower than in adults.

Non-steroidal anti-inflammatory drug hypersensitivity: association with elevated basal serum tryptase?

Background

It is hypothesized that because of higher mast cell numbers and mediator release, mastocytosis predisposes patients for systemic immediate-type hypersensitivity reactions to certain drugs including non-steroidal anti-inflammatory drugs (NSAID).

Objective

To clarify whether patients with NSAID hypersensitivity show increased basal serum tryptase levels as sign for underlying mast cell disease.

Methods

As part of our allergy work-up, basal serum tryptase levels were determined in all patients with a diagnosis of NSAID hypersensitivity and the severity of the reaction was graded. Patients with confirmed IgE-mediated hymenoptera venom allergy served as a comparison group.

Results

Out of 284 patients with NSAID hypersensitivity, 26 were identified with basal serum tryptase > 10.0 ng/mL (9.2%). In contrast, significantly (P = .004) more hymenoptera venom allergic patients had elevated tryptase > 10.0 ng/mL (83 out of 484; 17.1%). Basal tryptase > 20.0 ng/mL was indicative for severe anaphylaxis only in venom allergic subjects (29 patients; 4x grade 2 and 25x grade 3 anaphylaxis), but not in NSAID hypersensitive patients (6 patients; 4x grade 1, 2x grade 2).

Conclusions

In contrast to hymenoptera venom allergy, NSAID hypersensitivity do not seem to be associated with elevated basal serum tryptase levels and levels > 20 ng/mL were not related to increased severity of the clinical reaction. This suggests that mastocytosis patients may be treated with NSAID without special precautions.