A diagnostic workup of perioperative anaphylaxis reveals a selective type 1 hypersensitivity to cefazolin

Abstract: Anaphylaxis in the operating room although infrequent can be potentially fatal.1 The diagnosis of perioperative anaphylaxis is complex due to a multitude of factors. Firstly, patients under anesthesia cannot verbalize their complaints, the anesthetic agents themselves can alter vital parameters (e.g. heart rate and blood pressure) and cutaneous signs in a completely draped patient may be missed.2 Secondly, the differential diagnosis of intraoperative anaphylaxis is wide. Conditions such as asthma exacerbation, arrhythmia, hemorrhage, angioedema, mastocytosis, acute myocardial infarction, drug overdose, pericardial tamponade, pulmonary edema, pulmonary embolus, sepsis, tension pneumothorax, vasovagal reaction, venous air embolism, laryngospasm, blood transfusion reaction and malignant hyperthermia need to be considered.3 Thirdly, the diagnostic workup is challenging due to the multiple medications administered and other exposures encountered such as latex and chlorhexidene. However, through a timely allergy consultation and a systematic approach, identification of the culprit agent and safe alternatives can be established to prevent future occurrences as illustrated in the case below.

A review of oral food challenges in children presenting to a single tertiary centre with perceived or true food allergies

<p><b>INTRODUCTION</b>The prevalence of perceived food allergies exceeds that of true food allergies. Unnecessary food avoidance may increase parental and patient anxiety, reduce quality of life and increase the risk of nutritional deficiency. An oral food challenge (OFC) can provide an objective measure regarding the presence or absence of food allergies in a child. This study reviews the indications for and outcomes of OFCs performed on children.</p><p><b>METHODS</b>A retrospective review was performed on all children who underwent OFCs at the Allergy Unit of the National University Hospital, Singapore, over a three-year period.</p><p><b>RESULTS</b>A total of 197 OFCs were performed among 58 patients (34 male, 24 female). Most of the tests were for allergies to tree nuts (n = 107). Among the OFCs, 43.1% were for foods that were avoided and never eaten due to perceived food allergies, 25.9% were for foods that had previously resulted in positive skin prick tests (SPTs) and/or immunoassay results, 16.2% were for foods thought to worsen eczema and 14.7% were for foods thought to have caused a previous reaction. Of all the OFCs, 5% were positive, although adverse reactions were mostly cutaneous. Challenge-positive patients had either positive SPTs (wheal > 3 mm) or raised serum immunoglobulin E levels to specific foods that they reacted to during the challenges. No episodes of anaphylaxis were reported after the challenge. Most of the patients were able to safely introduce the avoided foods into their diets.</p><p><b>CONCLUSION</b>OFCs provide an objective assessment for suspected food allergies.</p>

Allergies in Asia: are we facing an allergy epidemic?

No abstract available.

Food allergy in Asia: how does it compare?

Asia is a populous and diverse region and potentially an important source of information on food allergy. This review aims to summarize the current literature on food allergy from this region, comparing it with western populations. A PubMed search using strategies "Food allergy AND Asia", "Food anaphylaxis AND Asia", and "Food allergy AND each Asian country" was made. Overall, 53 articles, published between 2005 and 2012, mainly written in English were reviewed. The overall prevalence of food allergy in Asia is somewhat comparable to the West. However, the types of food allergy differ in order of relevance. Shellfish is the most common food allergen from Asia, in part due to the abundance of seafood in this region. It is unique as symptoms vary widely from oral symptoms to anaphylaxis for the same individual. Data suggest that house dust mite tropomysin may be a primary sensitizer. In contrast, peanut prevalence in Asia is extremely low compared to the West for reasons not yet understood. Among young children and infants, egg and cow's milk allergy are the two most common food allergies, with prevalence data comparable to western populations. Differences also exist within Asia. Wheat allergy, though uncommon in most Asian countries, is the most common cause of anaphylaxis in Japan and Korea, and is increasing in Thailand. Current food allergy data from Asia highlights important differences between East and West, and within the Asian region. Further work is needed to provide insight on the environmental risk factors accounting for these differences.

Clinical characteristics and outcomes of patients undergoing drug provocation tests (DPTs)

<p><b>INTRODUCTION</b>Patients who have an adverse drug reaction are frequently labelled drug allergic without undergoing proper evaluation and confirmatory testing. These drug allergy labels may be inaccurate, leading to unnecessary lifelong avoidance. The aim of this study was to review the patients that underwent drug provocation tests (DPTs) in our centre and examine the usefulness of DPTs in confirming or rejecting a diagnosis of drug hypersensitivity.</p><p><b>MATERIALS AND METHODS</b>The study design was a retrospective chart review of all adult patients who underwent drug provocation in the allergy unit at the National University Hospital, Singapore, for single or multiple suspected drug allergies from the period January 2009 to June 2011.</p><p><b>RESULTS</b>Eighty-seven patients underwent 123 DPTs (median age 41; interquartile range 28 to 50). Twenty-one patients underwent multiple DPTs. The most common culprit drugs reported were antibiotics (43.9%) of which beta-lactams were implicated in 75.9% of the cases. This was followed by non-steroidal anti-inflammatory drugs (NSAIDS) in 15.4%, paracetamol in 7.3% and both NSAIDs and paracetamol in 3.3%. Rash was the most commonly reported symptom (41.5%), followed by angioedema (32.5%), anaphylaxis (9.8%), and other symptoms including respiratory (2.4%), gastrointestinal (0.8%) and others (13.0%). The majority of DPTs were performed to antibiotics (43.9%), NSAIDs (19.5%) and paracetamol (6.5%). DPTs were negative in 93.5% of subjects and positive in 6.5%. Of the 8 positive DPTs, none had a serious reaction, with 5 patients requiring rescue therapy, which comprised solely of oral antihistamines.</p><p><b>CONCLUSION</b>Suspected drug hypersensitivity is common but true drug allergy is rare. DPTs remain the gold standard and should be included as part of an investigative protocol. DPTs are a safe and valuable diagnostic tool in the hands of the experienced clinician.</p>