Mast cell tryptase and hemolysis after trauma

Relationship between Tryptase and Hypotension in Anaphylaxis during Anesthesia

INTRODUCTION

Hypotension is a cardiovascular symptom that appears at the onset of anaphylaxis. It is considered an important factor as it affects the severity of anaphylaxis; however, its details remain to be elucidated. In this study, we investigated the characteristics of hypotension at the onset of anaphylaxis during anesthesia, along with the relationship between hypotension, tryptase and histamine.

MATERIALS AND METHODS

The minimum systolic blood pressures of patients diagnosed with anaphylaxis using the clinical diagnostic criteria of the World Allergy Organization guidelines were extracted from electronic anesthesia records. We analyzed changes in tryptase and histamine that were measured after the onset of anaphylaxis. We analyzed the relationship of tryptase and histamine with the minimum systolic blood pressure and the severity of anaphylaxis.

RESULTS

Of 55,996 patients, 25 were diagnosed with anaphylaxis during anesthesia (0.045%). Among these patients, the minimum systolic blood pressure was less than 90 mmHg. Furthermore, the minimum systolic blood pressure was inversely correlated with tryptase levels immediately to 1 hour, and 2 to 4 hours after the onset of anaphylaxis. The minimum systolic blood pressure was inversely correlated with the severity of anaphylaxis. The severity of anaphylaxis was positively correlated with tryptase levels immediately to 1 hour, and 2 to 4 hours after the onset of anaphylaxis.

CONCLUSION

Hypotension tended to reflect the severity of anaphylaxis. Tryptase is an adjunct in the diagnosis of hypotension and may be a useful indicator of the severity of anaphylaxis. A larger-scale study is needed to validate these results.

Post COVID-19 vaccine deaths - Singapore's early experience

Singapore has been using mRNA vaccines developed by Pfizer-BioNTech and Moderna as part of the nation's COVID vaccination program since 30 December 2020. From 1 February 2021-30 June 2021, a total of 34 deaths that occurred within 72 h of the deceased receiving their COVID-19 vaccination were referred to the Forensic Medicine Division of the Health Sciences Authority of Singapore. Autopsies, histological sampling and ancillary investigations consisting of total tryptase level, Immunoglobulin E (IgE), and C-reactive Protein (CRP), were performed on 29 of these cases. Our study has shown no definite causative relationship between the mRNA vaccination and deaths of individuals who died within 72 h after receiving the vaccination, in particular with regards to anaphylactic reactions, myocarditis and pericarditis, and thrombotic complications. Further studies may consider increasing the incident time frame from 72 h to seven days post-vaccination or longer to include any potential delayed presentation of adverse effects.

Levels of haemolysis have no effect on femoral vein post-mortem tryptase levels

Haemolysis is reported to be an artefact that may alter post-mortem tryptase levels. However, previous studies did not sample peripheral blood using newly standardised methods. Recent studies have shown that some previously recognised peri- and post-mortem confounders can be muted by careful sample collection with first clamping and then sampling the femoral vein. This prospective study investigated the relationship between the degree of haemolysis of the blood samples and femoral vein post-mortem tryptase levels when sampled using this recommended method. Seventy consecutive post-mortem tryptase levels in non-anaphylactic deaths were compared to the degree of haemolysis of these samples, and results showed no significant correlation between them. The mean post-mortem tryptase level was 9.5 μg/L. This study demonstrated that the effects of haemolysis on femoral vein post-mortem tryptase was negligible when the blood was sampled using the recommended sampling method. Future studies on post-mortem tryptase as well as other typically used blood markers in forensics are recommended to adopt this method of blood sampling in routine practice.

Differences Between Central and Peripheral Postmortem Tryptase Levels

ABSTRACT

Postmortem tryptase is a commonly used biochemical test to aid in the diagnosis of fatal anaphylaxis, which is currently recommended to be sampled from peripheral (femoral) veins because of a research showing comparatively elevated levels from central blood sources. Previous studies have used nonstandardized or nondocumented sampling methods; however, more recent research demonstrates that tryptase levels may vary depending on the sampling method. This study used the recommended sampling method of aspirating the femoral vein after clamping and compared in a pairwise comparison with aspiration of central venous and arterial blood sources (inferior vena cava and aorta) in 2 groups of 25 nonanaphylactic deaths. We found no statistically significant differences in postmortem tryptase between central and femoral vein blood; however, sporadic outliers in central blood (particularly aortic blood reaching levels above documented cutoffs for fatal anaphylaxis) were observed. Our findings provide evidence for the existing recommendations that femoral vein blood remains the preferred sample for postmortem tryptase over central blood.

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.

Human serum mast cell tryptase levels in elbow fractures or dislocations and its association with injury severity

Mast cells contain an abundance of tryptase, and preclinical models have shown elevated serum mast cell tryptase (SMCT) in the setting of posttraumatic joint contractures. Therefore, SMCT emerged as a potential biomarker to help recognize patients with more severe injuries and a higher likelihood of developing contractures. The objective of this study is to assess SMCT levels in participants with varying severity of elbow fractures and/or dislocations. A prospective cohort including 13 participants with more severe injuries that required an operation and 28 participants with less severe injuries managed nonoperatively were evaluated. A control group of eight individuals without elbow injuries was also evaluated. The SMCT levels were measured using an enzyme-linked immunosorbent assay kit specific for human mast cell tryptase. A one-way analysis of variance and Tukey's Honest Significance test was used to assess for statistical significance among and between the three groups. The average time from injury to the collection of the blood samples was 4 ± 2 days. Highly significant differences were identified between the operative, nonoperative, and control groups (P = .0005). In the operative group, SMCT levels were significantly higher than the nonoperative group (P = .0005) and the control group (P = .009), suggesting a correlation between SMCT levels and injury severity. There was no statistically significant difference in SMCT levels between the nonoperative and control groups. The SMCT levels were elevated in participants with acute elbow injuries requiring operative intervention, suggesting that SMCT levels were higher in injuries regarded as more severe.

Post mortem tryptase: A review of literature on its use, sampling and interpretation in the investigation of fatal anaphylaxis

Post mortem tryptase is a commonly-used ancillary test in the investigation of possible anaphylactic deaths. Ante mortem tryptase interpretation differs from post mortem interpretation due to differing priorities, biochemical behaviours and capacity for follow-up. Additionally, post mortem tryptase sampling site, method and even cut-off levels are not standardised between facilities. This review of the literature investigates the existing research and recommendations on the use of post mortem tryptase in suspected anaphylactic deaths. Currently, autopsy recommendations suggest early sampling, standardised sampling technique with clamping of and aspiration from the femoral vein, and for the results to be interpreted within the wider autopsy and clinical context. Areas in need of further research include the effects of cytolysis on tryptase levels and studies to stratify differing tryptase levels based on type of death and anaphylactic trigger.

Postmortem Tryptase Level in 120 Consecutive Nonanaphylactic Deaths: Establishing a Reference Range as <23 μg/L

Postmortem tryptase is a useful biochemical test to aid the diagnosis of anaphylaxis. Multiple perimortem and postmortem factors have been documented to cause an elevation in postmortem tryptase level. One factor that was recently recognized to have an impact on postmortem tryptase level is correct sampling technique. A recent study recommended aspirating blood samples from a clamped femoral/external iliac vein to be used for reliable postmortem tryptase analysis. This study sampled 120 consecutive nonanaphylactic deaths in which all the peripheral bloods were sampled as recommended. Postmortem interval, resuscitation, different nonanaphylactic causes of death, sex, and age did not show any statistical significant relation to postmortem tryptase level in Student t test, Pearson correlation, and univariate and multivariate analyses. The mean (SD) postmortem tryptase level was 8.4 (5.2) μg/L (minimum, 1.0 μg/L; maximum, 36.1 μg/L; median, 7.3 μg/L). Using nonparametric methods, the postmortem tryptase reference range in nonanaphylactic death was established as <23 μg/L (97.5th percentile).

Biomarkers in Human Anaphylaxis: A Critical Appraisal of Current Evidence and Perspectives

Anaphylaxis is a type I hypersensitivity reaction that is potentially fatal if not promptly treated. It is a clinical diagnosis, although measurement of serial serum total mast cell tryptase (MCT) is gold standard and may help differentiate anaphylaxis from its mimics. The performance characteristics of MCT assays in anaphylaxis has been variable in previous studies, due to multiple factors including differences in the definition of anaphylaxis, methods of MCT interpretation, clinical setting of anaphylaxis, causative agents, and timing of blood sample. An international consensus equation for MCT to interpret mast cell activation has been proposed and recently validated in the context of peri-operative anaphylaxis during general anesthesia. There has been an interest in the detection of newer biomarkers in anaphylaxis including platelet activation factor (PAF), chymase, carboxypeptidase A3, dipeptidyl peptidase I (DPPI), basogranulin, and CCL-2. The key determinants of an ideal biomarker in anaphylaxis are half-life, sample handling and processing requirements, and cost. There may be a role for metabolomics and systems biology in the exploration of novel biomarkers in anaphylaxis. Future studies applying these approaches might provide greater insight into factors determining severity, clinical risk stratification, identification of mast cell disorders and improving our understanding of this relatively complex acute immunological condition. Post mortem MCT evaluation is used in Forensic Medicine during autopsy for cases involving sudden death or suspected anaphylaxis. Interpretation of post mortem MCT is challenging since there is limited published evidence and the test is confounded by multiple variables largely linked to putrefaction and site of sampling. Thus, there is no international consensus on a reference range. In this state of the art review, we will focus on the practical challenges in the laboratory diagnosis of anaphylaxis and critically appraise (a) performance characteristics of MCT in anaphylaxis in different clinical scenarios (b) the role for novel biomarkers and (c) post mortem MCT and its role in fatal anaphylaxis.

The effects of different sampling techniques on peripheral post mortem tryptase levels: a recommended sampling method

Different sampling techniques can impact on post mortem tryptase levels. A previous study demonstrated significantly lower femoral post mortem total tryptase levels in samples collected via transcutaneous aspiration compared with directly sampling during internal examination. However, an outlier with high tryptase level was noted in one transcutaneous aspiration sample. This 6-month prospective study compared total post mortem tryptase levels between 21 paired aspirated venous and arterial femoral blood samples, and 19 paired aspirated and cutdown femoral venous blood samples in non-anaphylactic deaths only. No statistical differences were demonstrated between the different sampling methods. However, four outlier cases with higher tryptase levels in aspirated arterial and femoral cutdown samples compared with aspirated venous femoral samples were noted. The reasons for the outliers may be due to the bloods collected from these two methods being contaminated by central arterial and venous blood with high tryptase levels respectively. None of the aspirated venous femoral post mortem tryptase levels were above recognized post mortem tryptase cutoff to diagnose anaphylaxis. This study recommends aspirating blood samples from a clamped femoral/external iliac vein for post mortem tryptase analysis should be defined as the gold standard. Further study using the recommended sampling method on post mortem tryptase levels in non-anaphylactic and anaphylactic cases is warranted.

Inflammatory reaction patterns of the lung as a response to alveolar hypoxia and their significance for the diagnosis of asphyxiation

Providing evidence of asphyxia death is a challenging issue in forensic pathology. Besides helpful macroscopical signs (e.g. strangulation mark, lung edema), recent data from literature indicate that the time of protracted asphyxia suffices to trigger an increase of giant cells and a migration of inflammatory cells from the bone marrow to the lung, thus offering a help in diagnosis of asphyxia death. In search of new valid asphyxia markers, the present study examined this hypothesis and investigated the leading role of pre-existing lung tissue cells and their functional state in reaction patterns to asphyxia. In specimens of suffocated human lungs following a short (n = 13) and a long asphyxia terminal episode (n = 15), and controls (sudden cardiovascular (n = 11) and traumatic deaths (n = 7)), the count of alveolar phagocytes, megakaryocytes, giant and mast cells, using H&E and toluidine blue staining, was performed. To show macrophage activation, immunohistochemical stainings for CD68, late (25F9) and early (MRP-8/-14) stage inflammatory markers were used. Measuring concentration of tryptase in femoral blood acted as a parameter for mast cell degranulation and consequently their activation. Results showed the lack of specificity of macroscopical parameters despite an association of suffocation with heavy lung edema. No significant differences in the numbers of inflammatory cells in the lungs of different case groups were detected. The doubling of MRP-8- and a five-fold elevation of MRP-14-positive cells compared to cardiovascular controls, proved an early activation state of pre-exiting monocytes in protracted asphyxia. These activated monocytes induced the degranulation of mast cells, resulting in slightly elevated tryptase levels in suffocation compared to cardiovascular controls. In summary, the duration of asphyxia (max. 20 min in cases investigated) only suffices to cause changes on molecular level, being not detectable in any specific macroscopical or histological form in the lung. Despite a potential utility of this molecular insight in individual cases, these results point to the classic doctrine of the evaluation of a rounded overall picture, accentuating on the proof of the ligature tool and the marks of suffocation process.

Post mortem tryptase cut-off level for anaphylactic death

Serum mast cell tryptase is used to support the diagnosis of anaphylaxis. The recommended clinical cut-off for total tryptase (<11.4μg/L) appears unsuitable in the post mortem setting due to largely unknown processes which result in significantly elevated levels in these samples. Consequently there is no widely accepted tryptase cut-off level for diagnosing an anaphylactic death. This 5-year retrospective study compared total tryptase levels in post mortem femoral blood in anaphylactic deaths and control. Univariate and multivariate analysis was used to assess the relative contribution of other factors (age, gender, post mortem interval, and presence of resuscitation) on post mortem tryptase levels. Nine anaphylactic deaths and 45 controls were identified. Receiver-operating characteristic (ROC) curve analysis identified an optimal cut-off of 53.8μg/L, with sensitivity of 89%, and specificity of 93%, for total post mortem tryptase in femoral blood to diagnosis anaphylaxis. No other factors showed any statistical significant contribution to post mortem tryptase elevation. Femoral total post mortem tryptase level of 53.8μg/L and above is a useful ancillary test in diagnosing an anaphylactic death.

Postmortem biochemistry: Current applications

The results of biochemical analyses in specimens obtained postmortem may aid death investigation when diabetic and alcoholic ketoacidosis is suspected, when death may have been the result of drowning, anaphylaxis, or involved a prolonged stress response such as hypothermia, and in the diagnosis of disease processes such as inflammation, early myocardial infarction, or sepsis. There is often cross-over with different disciplines, in particular with clinical and forensic toxicology, since some endogenous substances such as sodium chloride, potassium chloride, and insulin can be used as poisons. The interpretation of results is often complicated because of the likelihood of postmortem change in analyte concentration or activity, and proper interpretation must take into account all the available evidence. The unpredictability of postmortem changes means that use of biochemical measurements in time of death estimation has little value. The use of vitreous humour is beneficial for many analytes as the eye is in a physically protected environment, this medium may be less affected by autolysis or microbial metabolism than blood, and the assays can be performed with due precaution using standard clinical chemistry analysers. However, interpretation of results may not be straightforward because (i) defined reference ranges in life are often lacking, (ii) there is a dearth of knowledge regarding, for example, the speed of equilibration of many analytes between blood, vitreous humour, and other fluids that may be sampled, and (iii) the effects of post-mortem change are difficult to quantify because of the lack of control data. A major limitation is that postmortem vitreous glucose measurements are of no help in diagnosing antemortem hypoglycaemia.

Fatal laryngeal angioedema: a case report and a workup of angioedema in a forensic setting

Angioedema is an episodic swelling of the deep dermis, subcutis, and/or submucosal tissue due to an increase in local vascular permeability. Swelling may involve skin, respiratory, and gastrointestinal tracts. The most commonly involved areas are the periorbital region and the lips. Here we report a case of a fatal laryngeal obstruction due to angioedema likely caused by an angiotensin-converting-enzyme inhibitor. The decedent, a 58-year-old man, was witnessed developing sudden facial swelling and acute respiratory difficulties quickly followed by unresponsiveness. His past medical history suggested that this was his second episode of angioedema without urticaria. Postmortem examination revealed a complete laryngeal obstruction in the absence of infection, neoplasm, or autoimmune disease. Postmortem computed tomography of the head and neck showed a complete obstruction of the upper airway. Based on the current understanding of the pathophysiology of different types of angioedema, we will suggest a workup of angioedema without urticaria in the forensic setting and offer readers resources they can use in their practice.

Food allergy testing

Food allergy (IgE-mediated hypersensitivity) is a common clinical problem affecting approximately 15% of children in the Western world. These hypersensitivity reactions tend to be "immediate" (typically within minutes of food exposure), and clinical features may range from mild to life threatening (anaphylaxis). Detailed clinical history is critical to correct diagnosis. Available laboratory tests have limitations not least poor positive predictive value and limited repertoire. Laboratory tests should support clinical diagno sis not vice versa.

Measurement of β-tryptase in postmortem serum, pericardial fluid, urine and vitreous humor in the forensic setting

In the realm of forensic pathology, β-tryptase measurement for diagnostic purposes is performed in postmortem serum obtained from femoral blood. This may be partially or completely unavailable in some specific cases, such as infant autopsies and severely damaged bodies. The aim of this study was to investigate the usefulness of determining β-tryptase levels for diagnostic purposes in alternative biological samples. Urine, vitreous humor and pericardial fluid were selected and measured in 94 subjects including: fatal anaphylaxis following contrast material administration (6 cases), hypothermia (10 cases), diabetic ketoacidosis (10 cases), gunshot suicide (10 cases), heroin injection-related deaths (18 cases), trauma (10 cases), sudden death with minimal coronary atherosclerosis (10 cases), severe coronary atherosclerosis without myocardial infarction (10 cases) and severe coronary atherosclerosis with myocardial infarction (10 cases). Postmortem serum and pericardial fluid β-tryptase levels higher than the clinical reference value (11.4ng/ml) were systematically identified in fatal anaphylaxis following contrast material administration and 6 cases unrelated to anaphylaxis. β-tryptase concentrations in urine and vitreous humor were lower than the clinical reference value in all cases included in this study. Determination of β-tryptase in pericardial fluid appears to be a possible alternative to postmortem serum in the early postmortem period when femoral blood cannot be collected during autopsy and biochemical investigations are required to objectify increased β-tryptase levels.

Postmortem serum tryptase levels in anaphylactic and non-anaphylactic deaths

BACKGROUND

The postmortem diagnosis of anaphylaxis remains difficult due to the lack of specific biomarkers. Mast cell tryptase (MCT) levels are used as a marker of mast cell degranulation in living patients and elevated levels have also been described in postmortem serum samples in anaphylaxis-associated deaths, although elevated levels may also be seen in non-anaphylaxis-associated deaths.

OBJECTIVE

To investigate the effects of cause of death, site of blood sampling, degree of sample haemolysis and the presence of opiates on postmortem MCT levels.

METHOD

We obtained sera from three collection sites from 189 non-suspicious coronial postmortems and aortic samples from 10 anaphylactic deaths to characterise postmortem MCT.

RESULTS

MCT were elevated (>11.4 μg/L) in 57% of aortic samples, 58% of femoral samples and 30% of subclavian samples. In aortic samples, there were significantly higher levels of MCT in anaphylaxis-associated deaths compared with other causes of death. Aortic MCT levels >110 μg/L had a sensitivity of 80% and specificity of 92.1% for anaphylaxis-associated deaths. There was a significant correlation between MCT and degree of sample haemolysis but no correlation with the presence of opiates.

CONCLUSIONS

Moderately elevated MCT levels are common in postmortem sera. Aortic values >110 μg/L may support a diagnosis of anaphylaxis-associated death, although the diagnosis should not be based on this test alone. There was significant variation between sample sites and reference ranges for individual sample sites should be established.

Usefulness of post mortem determination of serum tryptase, histamine and diamine oxidase in the diagnosis of fatal anaphylaxis

The diagnosis of fatal anaphylaxis can be difficult for clinical features may not always be evident in necropsy. Therefore post mortem determination of tryptase and other blood parameters can be helpful in verifying the diagnosis. We compared post mortem tryptase, histamine and diamine oxidase (DAO) serum levels of two patients who had died after a Hymenoptera sting and one patient who died of bronchospasm during anaesthesia with data obtained from 55 control subjects who had died from other causes than anaphylaxis. In the three anaphylactic cases, serum tryptase level was 880, 68 and 200 μg/l (normal range in living subjects: <11.4 μg/l), histamine was 37.5, 8.5 and 23.2 ng/ml (normal range: <0.3 ng/ml) and DAO was 1, 30 and 4 U/ml (normal range 10-30 U/ml), respectively. Values in the control group were as follows: tryptase 1-340 μg/l (mean 24.2 ± 58.2), histamine 5.0-22.0 ng/ml (mean 14.7 ± 3.9) and DAO 0-114 U/ml (mean 21.1 ± 27.8). 19/55 (34.5%) of the controls had elevated tryptase levels >11.4 μg/l, with four of them showing values >45 μg/ml. Significantly higher histamine levels were seen in blood samples taken more than 24h post mortem (p<0.05), whereas the timing of blood collection had no effect on tryptase and DAO levels. While moderately elevated tryptase levels are common in post mortem sera, values above 45 μg/l may support the diagnosis of fatal anaphylaxis. Strongly elevated histamine levels might give an additional clue on fatal anaphylaxis, whereas DAO does not seem to be helpful.

The diagnosis and management of anaphylaxis practice parameter: 2010 update

These parameters were developed by the Joint Task Force on Practice Parameters, representing the American Academy of Allergy, Asthma & Immunology (AAAAI); the American College of Allergy, Asthma & Immunology (ACAAI); and the Joint Council of Allergy, Asthma and Immunology. The AAAAI and the ACAAI have jointly accepted responsibility for establishing "The Diagnosis and Management of Anaphylaxis Practice Parameter: 2010 Update." This is a complete and comprehensive document at the current time. The medical environment is a changing environment, and not all recommendations will be appropriate for all patients. Because this document incorporated the efforts of many participants, no single individual, including those who served on the Joint Task Force, is authorized to provide an official AAAAI or ACAAI interpretation of these practice parameters. Any request for information about or an interpretation of these practice parameters by the AAAAI or ACAAI should be directed to the Executive Offices of the AAAAI, the ACAAI, or the Joint Council of Allergy, Asthma and Immunology. These parameters are not designed for use by pharmaceutical companies in drug promotion.

Mast cells: novel clinical perspectives from recent insights

Mast cells are still generally viewed as mediators of type I allergic or pseudoallergic reactions. Research over the past 10 years revealed that our view was too small and that mast cells are of key importance in innate immunity and also types II, III and IV adaptive immune reactions. Understanding their role in modulating and amplifying of inflammatory responses provides important insights into the pathogenesis of skin diseases such as psoriasis, atopic dermatitis, bullous pemphigoid or the control of infections. This helps us to understand the course of these diseases, their trigger mechanisms, and, the new role of agents, which can modulate the function of mast cells. These insights will help to develop new therapeutic approaches.

Sudden adult death

In the investigation of sudden death in adults, channelopathies, such as long QT syndrome, have risen to the fore in the minds of forensic pathologists in recent years. Examples of these disorders are touched upon in this review as an absence of abnormal findings at postmortem examination is characteristic and the importance of considering the diagnosis lies in the heritable nature of these conditions. Typically, a diagnosis of a possible channelopathy is evoked as an explanation for a 'negative autopsy' in a case of apparent sudden natural death. However, the one potential adverse effect of this approach is that subtle causes of sudden death may be overlooked. The intention of this article is to review and discuss potential causes of sudden adult death (mostly natural) that should be considered before resorting to a diagnosis of possible channelopathy. Nonetheless, it becomes apparent that many of the potential causes of sudden death can have a genetic basis. Thus, it becomes an important consideration that there may be a genetic basis to sudden death that extends beyond the negative autopsy.

Anaphylactic deaths in Maryland (United States) and Shanghai (China): a review of forensic autopsy cases from 2004 to 2006

Anaphylaxis is a life threatening allergic reaction that is rapid in onset and may cause sudden death. A retrospective study was performed using the database from the Office of the Chief Medical Examiner (OCME) in the State of Maryland and the Department of Forensic Medicine in Shanghai Medical College (DFM-SMC) to examine the etiology and forensic investigation findings of anaphylactic deaths from 2004 to 2006. Details of the medical history, agent responsible for the allergic reaction, death scene investigation and postmortem examination findings were reviewed for all cases. A total of 28 cases of anaphylactic death were identified for the study period, 17 from Maryland and 11 from Shanghai. Of the 17 Maryland cases, 6 (35%) involved allergic reaction to food, 5 (25%) to drugs, 2 to bee stings, 1 to hair dye, and 3 to unknown allergens. Investigation revealed that 9 of 17 cases had a history of asthma and 8 had previous allergic reactions to certain foods and / or drugs. In Shanghai, all 11 deaths resulted from anaphylactic reaction to antibiotics, 10 of which occurred in clinics illegally operated by unlicensed physicians. The interval between the onset of symptoms and death ranged from less than 1 min to 3 days after initially contacting the allergen. In the majority (68%) of cases, death occurred within 8h after the onset of symptoms. Postmortem findings were relatively non-specific, and included pharyngeal/laryngeal edema 14/28 (50%), mucus plugging in the airways 11/28 (39%), and pulmonary congestion and edema 28/28 (100%). Serum tryptase concentrations were measured in 14 cases in Maryland and the concentration ranged from 3.3 ng/ml to 200 ng/ml. There were significant differences with regards to allergen type and the circumstances of death between these two regions. Inappropriate use of antibiotics and illegal medical practices were the main causes of identified anaphylactic death in Shanghai. In Maryland anaphylactic deaths were mainly caused by food reactions. This study indicates that the postmortem diagnosis of anaphylactic death is usually based on exclusion and circumstantial evidence. Knowledge of the patient's history and circumstances of death is of major importance for the forensic pathologist when investigating suspected anaphylactic death.

Tryptase levels after suxamethonium administration and defibrillation

BACKGROUND

A more than threefold increase in tryptase, when comparing with the control sample, strengthens the diagnosis of anaphylaxis. Trauma, coronary ischaemia and non-IgE-mediated reactions to several medications have been shown to cause more than threefold rise in tryptase levels. The aim of our study was to examine whether suxamethonium or defibrillation could lead to a more than threefold increase in tryptase in the absence of signs of anaphylaxis.

METHODS

S-tryptase was measured in 50 patients who had general anaesthesia with either pentothal and suxamethonium before electro convulsive therapy (ECT) to treat depression (n=31) or propofol before electro conversion to treat atrial fibrillation (n=19). Blood samples were collected minutes before and 1 h after the procedures.

RESULTS

Tryptase values did not differ significantly before and after the procedures.

CONCLUSION

Tryptase levels do not increase in patients undergoing elective defibrillation or ECT with the administration of suxamethonium, in absence of symptoms of anaphylaxis.

Mast cell tryptase in postmortem serum-reference values and confounders

We have investigated the effects of some factors suspected of inducing spuriously increased tryptase concentrations, specifically sampling site, conjunctival petechial bleeding and prone position at the time of death as indicators of premortem asphyxia, and resuscitation efforts by external cardiac massage. Tryptase was measured in blood from the femoral vein in 60 deaths: 39 control cases who died rapidly (within minutes) from natural causes (sudden cardiac death and acute aortic dissection), 16 with death caused by prolonged asphyxia (traumatic compression of the chest and suffocation due to body position or smothering), and five anaphylactic deaths. In 44 of these cases, tryptase was measured in both heart and femoral blood. Mast cell tryptase was analyzed with a commercial FEIA method (Pharmacia Diagnostics AB, Uppsala, Sweden) measuring both alpha- and beta-tryptase. Assuming that tryptase values in the control group were gamma distributed, we calculated the upper normal limits for tryptase concentrations in femoral blood. It was found that 95% of the controls had values below 44.3 mug/l (femoral blood), SD 5.27 mug/l. All but one of the anaphylactic deaths had tryptase concentrations exceeding that limit. Tryptase was significantly elevated in femoral blood from anaphylactic deaths (p<0.007), compared with the controls. Also, in the cases where death had occurred due to asphyxia tryptase was elevated in femoral blood (p<0.04). A significant difference in tryptase concentrations was seen between blood from the heart and the femoral vessels (p<0.02) in the whole material (n=44). Tryptase concentrations in femoral blood were not influenced by prone position at death, or resuscitation efforts. It is concluded that asphyxia premortem seems to affect tryptase concentrations, that postmortem tryptase measurements should be done in serum from femoral blood, and that the normal upper limit, covering 95%, is 44.3 microg/l.

Tryptase genetics and anaphylaxis

Tryptases secreted by tissue mast cells and basophils can enter the bloodstream. In human subjects tryptases are encoded by several genes and alleles, including alpha, beta, gamma, and delta. Common variations include complete absence of alpha genes. Until recently, alpha tryptase was considered to be the major tryptase secreted at baseline and in mastocytosis. However, lack of alpha tryptase genes has little effect on circulating tryptase levels, which are now thought mainly to consist of inactive pro-beta tryptase secreted constitutively rather than stored in granules with mature tryptases. Pro-beta tryptase levels thus might reflect total body mast cell content. In contrast, mature beta tryptase can increase transiently in severe systemic anaphylaxis and confirm the diagnosis. However, it might fail to increase in food anaphylaxis or might increase nonspecifically in samples acquired after death. Thus pro- and mature beta tryptase measurements are useful but associated with false-negative and false-positive results, which need to be considered in drawing clinical conclusions in cases of suspected anaphylaxis.

Induction of bone-marrow eosinophilia in mice submitted to surgery is dependent on stress-induced secretion of glucocorticoids

1 We examined bone-marrow in mice receiving subcutaneous implants of heat-coagulated egg white, which are known to present chronic eosinophilic inflammation at the implant site. Egg white implants (EWIs) induced marked bone-marrow eosinophilia, and increased bone-marrow cell responses to granulocyte-macrophage colony-stimulating factor and interleukin-5 in culture. These effects were observed as early as 24 h and lasted for, at least, 30 days in implant recipients. 2 We found, however, that increased eosinophil production was also observed in control mice which underwent surgery but received no EWI (sham-implanted mice), up to 15 days post-surgery. As this suggests an important contribution of nonspecific stress mechanisms to eosinopoiesis, we further evaluated the role of stress hormones produced by the adrenal glands in the bone-marrow eosinophilia of sham-implanted mice. 3 Bone-marrow eosinophilia in mice undergoing surgery was dissociated from increases in other haemopoietic lineages. Surgery by itself increased circulating corticosterone levels by 24 h, and the increase was prevented by inhibition of adrenal glucocorticoid production by metyrapone. The effect of surgery on bone-marrow eosinophilia was prevented by pretreatment with both the glucocorticoid receptor antagonist, mifepristone, and metyrapone, and by surgical adrenalectomy. 4 By contrast, cathecolamine receptor antagonists (propranolol, prazosin and yohimbine) were ineffective, indicating that cathecolamine release from the adrenal glands was not responsible for the effects on bone-marrow. 5 These results highlight a critical role for stress-induced glucocorticoid hormones in selectively upregulating bone-marrow eosinopoiesis in mice submitted to surgery.