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

Sandra M Salter; Ross J Marriott; Kevin Murray; Samantha L Stiles; Paul Bailey; Raymond J Mullins; Frank M Sanfilippo

doi:10.1016/j.waojou.2020.100480

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

World Allergy Organ J. 2020 Nov 13;13(11):100480. doi: 10.1016/j.waojou.2020.100480. eCollection 2020 Nov.

Authors

Sandra M Salter¹, Ross J Marriott², Kevin Murray², Samantha L Stiles¹, Paul Bailey³, Raymond J Mullins⁴, Frank M Sanfilippo⁵

Affiliations

¹ School of Allied Health, Faculty of Health and Medical Sciences, The University of Western Australia, M315, 35 Stirling Highway, Perth, WA, 6009, Australia.
² School of Population and Global Health, Faculty of Health and Medical Sciences, The University of Western Australia, Perth, WA, 6009, Australia.
³ St John WA, Belmont, Western Australia, 6104, Australia.
⁴ Suite 1, John James Medical Centre, 175 Strickland Crescent, Deakin, ACT, 2600, Australia.
⁵ School of Population and Global Health, The University of Western Australia, Perth, Western Australia, 6009, Australia.

Abstract

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.

Keywords: Anaphylaxis; Australia; EDDC, Emergency Department Data Collection; EPAWA, Epidemiology of Anaphylaxis in Western Australia; Epidemiology; Events; HMDC, Hospital Morbidity Data Collection; ICD-10-AM, International Statistical Classification of Diseases and Related Health Problems, 10th revision, Australian Modification; ICD-9-CM, International Classification of Diseases, 9th revision, Clinical Modification; IRSAD, Index of Relative Socio-Economic Advantage and Disadvantage; Linked data; SEIFA, Socio-Economic Indexes for Areas; WAAC, Western Australian Anaphylaxis Cohort; WADLS, Western Australian Data Linkage System.