Increasing anaphylaxis events in Western Australia identified using four linked administrative datasets.

BACKGROUND: Anaphylaxis events are increasing worldwide, based on studies of single administrative datasets including hospital admissions, emergency room presentations, and prescription and medical claims data. Linking multiple administrative datasets may provide better epidemiological estimates, by capturing a greater number of anaphylaxis events occurring at the individual level. In this linked data study in Western Australia, we combined 4 population-based datasets to identify anaphylaxis events, factors influencing occurrence, and change in event rates from 2002 to 2013. METHODS: Four linked administrative datasets from the Western Australian Data Linkage System were used, representing ambulance attendances, emergency department presentations, hospital inpatient admissions and death registrations. An anaphylaxis cohort was identified using ICD-9-CM, ICD-10-AM and additional anaphylaxis diagnosis codes, with event rates calculated. We explored the impact of age, gender, cause, Indigenous status and socioeconomic index on event rates. Standard Poisson regression models were used to examine the significance of the change in anaphylaxis event rates over time. RESULTS: A total 12,637 individuals (mean age 31.8 years, 49.6% female) experienced 15,462 anaphylaxis events between 2002 and 2013 (97.5% in non-Indigenous patients and 59.5% residing in the area of greatest socioeconomic advantage). Anaphylaxis event rates increased from 15.4 to 82.5/105 population between 2002 and 2013. The greatest increase in anaphylaxis events was seen in those coded as unspecified anaphylaxis (all ages, males and females combined, p < 0.001), with the highest rates of unspecified anaphylaxis in males 0-4 years (171.9/105 population in 2013), and females 15-19 years (104.0/105 in 2013). The average annual percent increase (95% CI) for food-related anaphylaxis was 9.2% (6.6-12.0); for medication-related anaphylaxis was 5.8% (4.5-7.1); and for unspecified anaphylaxis was 10.4% (9.8-11.0); all p < 0.001. There was a significant increase in ambulance attendance, emergency presentations and inpatient admissions for anaphylaxis between 2002 and 2013, with emergency presentations (56.0/105 population), inpatient admissions (43.2/105), and ambulance attendance (21.6/105) highest in 2013. Only 25 anaphylaxis-related deaths were recorded in the mortality register with no significant change in rates over time. CONCLUSION: Using multiple linked administrative datasets, we identified significantly higher rates of total anaphylaxis than previously reported, with more than 5-fold increases in anaphylaxis events between 2002 and 2013. While the combination of 4 population-level datasets provides a more comprehensive capture of cases, even at the individual dataset level, admission rates for anaphylaxis in Western Australia are substantially higher than those previously reported for similar time periods, both in Australia and worldwide.

Allergic gastroenteritis hospital admission time trends in Australia and New Zealand.

AIM: Recent epidemiological studies indicate increases in hospital food allergy-related anaphylaxis admission rates in Australian and New Zealand. The aim of the study was to examine whether non-IgE-mediated food allergy might have increased in parallel. METHODS: We analysed childhood hospital admissions rates by ICD 10 codes for allergic gastroenteritis (AG) and infective gastroenteritis in Australia and New Zealand between June 1998 and July 2014. RESULTS: In Australia, most AG-related admissions (73%) occurred in those aged <1 year and increased by 7.3%/year (95% confidence interval (CI) 5.5-9.3, P < 0.0001) from 6.8 to 26.5/105 population. Similar trends were observed for New Zealand; 81% of admissions occurred in those aged <1 year and increased by 9.4%/year (95% CI 5.5-9.3, P < 0.0001) from 7.2 to 30.7/105 population. By contrast there were no significant changes in AG-related admission rates in the older patients and infective gastroenteritis admissions fell in both countries in those aged <1 year; Australia by 4.4%/year (95% CI 4.3-4.6, P < 0.0001) and in New Zealand by 5.8%/year (95% CI 5.4-6.2, P < 0.0001). CONCLUSION: We observed a fourfold increase in AG-related admission rates in two countries with known high rates of IgE-mediated food allergy/anaphylaxis. If confirmed by other studies, it will be of interest to determine if factors thought to contribute to the increase in IgE-mediated food allergy might also play a role in non-IgE-mediated gastroenterological food allergy syndromes.

Food allergy: is prevalence increasing?

It is generally accepted that the prevalence of food allergy has been increasing in recent decades, particularly in westernised countries, yet high-quality evidence that is based on challenge confirmed diagnosis of food allergy to support this assumption is lacking because of the high cost and potential risks associated with conducting food challenges in large populations. Accepting this caveat, the use of surrogate markers for diagnosis of food allergy (such as nationwide data on hospital admissions for food anaphylaxis or clinical history in combination with allergen-specific IgE (sIgE) measurement in population-based cohorts) has provided consistent evidence for increasing prevalence of food allergy at least in western countries, such as the UK, United States and Australia. Recent reports that children of East Asian or African ethnicity who are raised in a western environment (Australia and United States respectively) have an increased risk of developing food allergy compared with resident Caucasian children suggest that food allergy might also increase across Asian and African countries as their economies grow and populations adopt a more westernised lifestyle. Given that many cases of food allergy persist, mathematical principles would predict a continued increase in food allergy prevalence in the short to medium term until such time as an effective treatment is identified to allow the rate of disease resolution to be equal to or greater than the rate of new cases.

Ant venom immunotherapy in Australia: the unmet need.

Jack jumper ant (JJA) venom allergy is an important cause of anaphylaxis in south-eastern Australia. The efficacy and real-world effectiveness of JJA venom immunotherapy (VIT) to prevent anaphylaxis in allergic patients are now well established, with an evidence base that is at least equivalent to that supporting VIT for allergy to other insect species. The tolerability and safety of JJA VIT are comparable with those of honeybee VIT.

Causes of ant sting anaphylaxis in Australia: the Australian Ant Venom Allergy Study.

OBJECTIVE: To determine the Australian native ant species associated with ant sting anaphylaxis, geographical distribution of allergic reactions, and feasibility of diagnostic venom-specific IgE (sIgE) testing. DESIGN, SETTING AND PARTICIPANTS: Descriptive clinical, entomological and immunological study of Australians with a history of ant sting anaphylaxis, recruited in 2006-2007 through media exposure and referrals from allergy practices and emergency physicians nationwide. We interviewed participants, collected entomological specimens, prepared reference venom extracts, and conducted serum sIgE testing against ant venom panels relevant to the species found in each geographical region. MAIN OUTCOME MEASURES: Reaction causation attributed using a combination of ant identification and sIgE testing. RESULTS: 376 participants reported 735 systemic reactions. Of 299 participants for whom a cause was determined, 265 (89%; 95% CI, 84%-92%) had reacted clinically to Myrmecia species and 34 (11%; 95% CI, 8%-16%) to green-head ant (Rhytidoponera metallica). Of those with reactions to Myrmecia species, 176 reacted to jack jumper ant (Myrmecia pilosula species complex), 18 to other jumper ants (15 to Myrmecia nigrocincta, three to Myrmecia ludlowi) and 56 to a variety of bulldog ants, with some participants reacting to more than one type of bulldog ant. Variable serological cross-reactivity between bulldog ant species was observed, and sera from patients with bulldog ant allergy were all positive to one or more venoms extracted from Myrmecia forficata, Myrmecia pyriformis and Myrmecia nigriceps. CONCLUSION: Four main groups of Australian ants cause anaphylaxis. Serum sIgE testing enhances the accuracy of diagnosis and is a prerequisite for administering species-specific venom immunotherapy.

Season of birth and food allergy in children.

BACKGROUND: The prevalence of food allergy is rising, and etiologic factors remain uncertain. Evidence implicates a role for vitamin D in the development of atopic diseases. Based on seasonal patterns of UV-B exposure (and consequent vitamin D status), we hypothesized that patients with food allergy are more often born in fall or winter. OBJECTIVE: To investigate whether season of birth is associated with food allergy. METHODS: We performed a multicenter medical record review of all patients presenting to 3 Boston emergency departments (EDs) for food-related acute allergic reactions between January 1, 2001, and December 31, 2006. Months of birth in patients with food allergy were compared with that of patients visiting the ED for reasons other than food allergy. RESULTS: We studied 1002 patients with food allergy. Of younger children with food allergy (age < 5 years), but not older children or adults, 41% were born in spring or summer compared with 59% in fall or winter (P = .002). This approximately 40:60 ratio differed from birth season in children treated in the ED for non-food allergy reasons (P = .002). Children younger than 5 years born in fall or winter had a 53% higher odds of food allergy compared with controls. This finding was independent of the suspected triggering food and allergic comorbidities. CONCLUSIONS: Food allergy is more common in Boston children born in the fall and winter seasons. We propose that these findings are mediated by seasonal differences in UV-B exposure. These results add support to the hypothesis that seasonal fluctuations in sunlight and perhaps vitamin D may be involved in the pathogenesis of food allergy.

Regional variation in infant hypoallergenic formula prescriptions in Australia.

There is little information on the regional distribution of food allergy in Australia. We examined the influence of latitude (a marker of sunlight/vitamin D status) on food allergy, as measured by 2007 infant hypoallergenic formula (IHF) prescription rates in children ages 0-2 yrs. Data were compiled from the 52 statistical divisions in mainland Australia plus the island of Tasmania (n=53 observations). Data from the Australian Department of Health and Aging and the Australian Bureau of Statistics were analysed by statistical division. There was significant regional variability in hypoallergenic formula prescription rates (per 100,000 population/yr), with the highest rates in southern Australia (14,406) and the lowest in the north (721), compared with a national average of 4099. Geographical factors (decreasing latitude and increasing longitude) were associated with a higher rate of IHF prescriptions, such that rates were higher in southern vs. northern regions, and in eastern compared with western regions. Controlling for longitude, physician density and markers of socioeconomic status, southern latitudes were associated with higher hypoallergenic formulae prescription rates [beta, -147.98; 95% confidence interval (CI)=-281.83 to -14.14; p=0.03]. Controlling for latitude, physician density and markers of socioeconomic status, eastern longitudes were also associated with higher hypoallergenic formulae prescription rates (beta, 89.69; 95% CI=2.90-176.49; p=0.04). Among young children, hypoallergenic formula prescription rates are more common in the southern and eastern regions of Australia. These data provide support for a possible role of sun exposure/vitamin D status (amongst other potential factors) in the pathogenesis of food allergy.

Paediatric food allergy trends in a community-based specialist allergy practice, 1995-2006.

OBJECTIVE: To examine changing demand for specialist food allergy services for children aged 0-5 years over the 12 years from 1995 to 2006 as an index of changing prevalence. DESIGN, SETTING AND PARTICIPANTS: Retrospective analysis of the records of 1489 children aged 0-5 years referred to a community-based specialist allergy practice in the Australian Capital Territory (population, about 0.33 million). MAIN OUTCOME MEASURES: Trends in demand for assessment for food allergy, dietary triggers and severity over 12 years, compared with Australian hospital morbidity data. RESULTS: 47% (697/1489) of 0-5 year-old children seen in private practice had food allergy (175 with food-associated anaphylaxis), most commonly to peanut, egg, cows milk and cashew. Over 12 years, the number of children in this age group evaluated each year increased more than fourfold, from 55 cases in 1995 to 240 in 2006. There was no change in the proportion diagnosed with allergic rhinitis in 1995 and 2006 (14.5% and 13.3%, respectively), urticaria (14.5% and 12.9%) or atopic eczema (54.5% and 57.0%). By contrast, the proportion with asthma dropped from 33.7% in 1995 to 12.5% in 2006 and the number with food allergy increased 12-fold, from 11 to 138 patients (and from 20.0% to 57.5% of children seen) The number with food anaphylaxis increased from five to 37 children (9.0% to 15.4%) over the same period. There were similar trends in age-adjusted Australian hospital admission rates for anaphylaxis in children aged 0-4 years, which increased from 39.3 to 193.8 per million population between the financial years 1993-94 and 2004-05, a substantially greater increase than for older age groups, or for the population as a whole (36.2 to 80.3 per million population). CONCLUSIONS: There is an urgent need for coordinated systematic studies of the epidemiology of food allergy in Australia, to ascertain risk factors and guide public health policy. An increased prevalence of food allergy has implications for public health and medical workforce planning and availability of allergy services in Australia.

Anaphylaxis: diagnosis and management.

Anaphylaxis is a serious, rapid-onset, allergic reaction that may cause death. Severe anaphylaxis is characterised by life-threatening upper airway obstruction, bronchospasm and/or hypotension. Anaphylaxis in children is most often caused by food. Bronchospasm is a common symptom, and there is usually a background of atopy and asthma. Venom- and drug-induced anaphylaxis are more common in adults, in whom hypotension is more likely to occur. Diagnosis can be difficult, with skin features being absent in up to 20% of people. Anaphylaxis must be considered as a differential diagnosis for any acute-onset respiratory distress, bronchospasm, hypotension or cardiac arrest. The cornerstones of initial management are putting the patient in the supine position, administering intramuscular adrenaline into the lateral thigh, resuscitation with intravenous fluid, support of the airway and ventilation, and giving supplementary oxygen. If the response to initial management is inadequate, intravenous infusion of adrenaline should be commenced. Use of vasopressors should be considered if hypotension persists. The patient should be observed for at least 4 hours after symptom resolution and referred to an allergist to assist with diagnosis, allergen avoidance measures, risk assessment, preparation of an action plan and education on the use of self-injectable adrenaline. Provision of a MedicAlert bracelet should also be arranged.