Anaphylaxis and clinical utility of real-world measurement of Acute Serum Tryptase in UK emergency departments

Background: British guidelines recommend that serial acute serum tryptase measurements be checked in all adults and a subset of children presenting with anaphylaxis. This is the first study reporting the clinical utility of acute serum tryptase in a “real-world” emergency department (ED) setting following the publication of the World Allergy Organization (WAO) criteria for anaphylaxis. Objectives: To (1) assess sensitivity, specificity, and positive and negative predictive values (PPV, NPV) of acute serum tryptase in anaphylaxis; (b) determine factors associated with higher acute serum tryptase levels; and (c) audit compliance of acute serum tryptase measurement in the ED. Methods: The methods used were retrospective electronic search for ED admissions to 3 acute care hospitals in Birmingham, UK, with anaphylaxis in 2012 using wide search terms followed by scrutiny of electronic clinical records and application of the WAO diagnostic criteria for anaphylaxis. Patients with an acute serum tryptase measurement were included in the analysis. Results: Acute serum tryptase level was measured in 141 of 426 (33.1%) cases. Mean time from the onset of symptoms to the measurement of acute serum tryptase level was 4 hours 42 minutes (SD ± 05:03 hours) and no patients had serial measurements conforming to British guidelines. Acute serum tryptase level of more than 12.4 ng/mL (75th centile) was associated with a sensitivity, specificity, PPV, and NPV of 28%, 88%, 0.93, and 0.17, respectively. Multiple regression analysis showed that male sex (odds ratio, 2.66; P = .003) and hypotension (odds ratio, 7.08; P = .001) predicted higher acute serum tryptase level. Conclusions: An acute serum tryptase level of more than 12.4 ng/mL in an ED setting carries high PPV and specificity, but poor sensitivity and NPV

A 17 year experience in perioperative anaphylaxis 1998-2015: harmonising optimal detection of mast cell mediator release.

BACKGROUND: Sheffield NARCOS (National Adverse Reactions Advisory Service) investigates suspected perioperative anaesthetic reactions using serial tryptase, urinary methylhistamine and clinical information. Further recommendations for additional allergy clinic assessment are provided. OBJECTIVE: To establish a robustly measurable protocol for identifying mast cell mediator (MMR) release in this cohort. To compare these thresholds with previous suggested thresholds and algorithms. METHOD: A review of 3,455 NARCOS cases referred with a suspected peri-operative allergic reaction. Tryptase, Urinary methylhistamine (UMH) and clinical details were analysed. 1746 cases were graded using the Ring and Messmer scale. Reaction grade, tryptase and UMH changes were compared with statistical and graphical presentations appropriate to non-normally distributed measurements using Analyse-IT software. RESULTS: Sensitive strategies such as 3μg/l or 20% are measurable, translatable and would substantially increase detection of potentially relevant changes in tryptases. Adequate quality assurance for low level measurement is needed. An incremental threshold of 20% would identify potential MMR in an additional 14% of cases with peak tryptase (Tp) between 5 and 14 μg/L and a further 15% with Tp below 5 μg/L. Further work is required to establish the diagnostic performance characteristics of this more sensitive approach. UMH also identified up to 120 further cases of potential MMR in absence of tryptase increments. CONCLUSION AND CLINICAL RELEVANCE: Future studies should establish and compare the predictive performance characteristics of each strategy against clinical phenotypes. A single agreed definition of positive serial tryptases is needed to enable robust evaluation of diagnostic strategies. This could serve as a harmonised standard for comparative studies of case series from different centres. This article is protected by copyright. All rights reserved

Epidemiology of severe anaphylaxis: can we use population-based data to understand anaphylaxis?

Purpose of review: The observed increase in incidence of allergic disease in many regions over the past 3 decades has intensified interest in understanding the epidemiology of severe allergic reactions. We discuss the issues in collecting and interpreting these data, and highlight current deficiencies in the current methods of data gathering. Recent findings: Anaphylaxis, as measured by hospital admission rates, is not uncommon and has increased in the UK, USA, Canada and Australia over the last 10-20 years. All large datasets are hampered by a large proportion of uncoded “unspecified” causes of anaphylaxis. Fatal anaphylaxis remains a rare event, but appears to be increasing for medication in Australia Canada and the USA. The rate of fatal food anaphylaxis is stable in the UK and USA, but has increased in Australia. The age-distribution for fatal food anaphylaxis is different to other causes, with data suggesting an age-related predisposition to fatal outcomes in teenagers and adults to the fourth decade of life. Summary: The increasing rates of food and medication allergy (the latter exacerbated by an ageing population) has significant implications for future fatality trends. An improved ability to accurately gather and analyse population level anaphylaxis data in a harmonised fashion is required, so as to ultimately minimise risk and improve management