Stormy weather: a retrospective analysis of demand for emergency medical services during epidemic thunderstorm asthmaBMJ 2017; 359 doi: https://doi.org/10.1136/bmj.j5636 (Published 13 December 2017) Cite this as: BMJ 2017;359:j5636
All rapid responses
Andrew et al. provide important reflections on responding to unprecedented emergency service demand during the latest Melbourne epidemic thunderstorm asthma (ETSA) event in 2016 (1, 2). The article has captured reactive responses to the acute crisis. However, there is also a need to consider proactive measures, beyond the immediate patient needs during an ETSA event. Key areas include identification of vulnerable patients, risk stratification, and adequate preventive measures.
Consistent with previous thunderstorm asthma epidemics (reviewed elsewhere (4)), this report also indicates that asthma was not a sufficient predictor of risk; only 228 of 615 patients attended by ambulance services (37%) had a pre-existing diagnosis of asthma (1). Bronchodilators appeared either not to be protective, or indicated uncontrolled asthma with consequent susceptibility to acute attacks. On the other hand, nearly all patients in this and previous ETSA episodes, had grass pollen allergy manifest as allergic rhinitis (hay fever) (3).
ETSA could therefore be mitigated by the identification of allergic rhinitis patients and appropriate therapy with nasal corticosteroids and existing beneficial, preventative allergen-specific immunotherapy treatment for grass pollen allergy (5, 6). Patients with concurrent asthma should be offered preventive inhaled corticosteroids according to guideline recommendations.
Among patients with hayfever, risk stratification may be achievable based on the degree of grass pollen sensitization. There is currently a gap in knowledge, particularly in Australia, on associations between skin prick test wheal diameter or concentrations of serum specific IgE to extracts of grass pollens, and vulnerability to severe hayfever and asthma symptoms. Interestingly, Bellomo et al. observed in a small group of patients who experienced asthma during earlier Melbourne ETSA events, larger size wheal reaction to ryegrass (Lolium perenne) pollen and allergen-containing ryegrass pollen starch granules in those affected by ETSA than control asthma patients presenting at other times (7). Whilst routine allergy tests are reported as dichotomous outcomes (a patient is sensitised or not based on a minimum cut off 3mm wheal diameter for SPT or 0.35 kU/L specific IgE for serology testing) (8), quantitative measurement of wheal size and specific IgE concentrations may better inform clinical management of allergy (9). Di Lorenzo et al. showed better outcomes for allergen immunotherapy in those with high proportion of specific /total IgE to allergen used in immunotherapy (10).
In longitudinal studies of children at risk for allergies, levels of specific IgE to grass pollen allergen components precede onset of allergic rhinitis and asthma (11); the group 1 pollen allergen (in that study Phl p 1 of timothy grass Phleum pratense) was the initiator allergen with serum IgE to Phl p 1 preceding onset of allergic rhinitis symptoms. Increases in serum IgE to the group 5 allergen (Phl p 5) emerged later and coincided with progression to asthma (11). Notably, it is the latter group 5 allergen of ryegrass pollen (Lol p 5) that is found within the ryegrass pollen starch granules (12). Such starch granules are released from ruptured grass pollen grains as small respirable size particles during thunderstorm asthma (13-15). Sensitisation to group 5 allergens may provide a direct immunological link between contact of the lower airways with Lol p 5 in airborne starch granules derived from ruptured pollen grains and allergic inflammation in the lungs during ETSA. In other contexts, thresholds of concentrations of specific IgE to allergen components of peanut may be associated with risk of clinical symptoms upon exposure to peanut (16, 17). Analogously, we hypothesise that locally relevant and measurable concentrations of specific IgE to key allergen components of ryegrass pollen, namely Lol p 1 and Lol p 5, could predict symptom severity and/or disease manifestation; allergic rhinitis and asthma, during ETSA (4).
The degree of underlying airway inflammation may also assist in risk stratification of patients. Preliminary reports suggest that exhaled nitric oxide may provide an indication of elevated risk for ETSA (18).
Education, public health responses including pollen and ETSA forecasting (19), and primary care control of known asthma are necessary to prevent acute thunderstorm asthma consequences for individuals and emergency and health services (15). To achieve good control of grass pollen allergy, patients are likely to benefit from integrated care from primary practice as well as respiratory and allergy physicians (5).
We reemphasise that an integral part of minimising impact of thunderstorm asthma in high risk areas like south eastern Australia is control of allergic rhinitis. More accurate quantitative diagnosis and uptake of allergen immunotherapy in those at-risk patients with allergic rhinitis and/or seasonal asthma, who are identified with high level of sensitisation to grass pollen allergens and relevant clinical symptoms, could help prevent ETSA.
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15. Chief Health Officer. The November 2016 Victorian epidemic thunderstorm asthma event: an assessment of the health impacts. In: Department of Health and Human Services, Victorian State Government; 2017. https://www2.health.vic.gov.au/emergencies/thunderstorm-asthma-event
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19. Victorian Health Department of Health and Human Services. Epidemic thunderstorm asthma forecasting. 2017 https://www2.health.vic.gov.au/public-health/environmental-health/climat....
Competing interests: JMD receives current grant funding from the NHMRC (AusPollen Partnership GNT 1116107) with co-contributions from The Australasian Society for Clinical Immunology and Allergy, Asthma Australia, Bureau of Meteorology, Commonwealth Scientific and Industrial Research Organisation, Stallergenes Australia, Meteorology Switzerland, Australian Research Council (DP170101630), the Bureau of Meteorology on a Thunderstorm Asthma Pollen Forecasting Project, the National Foundation of Medical Research Innovation. She has received grants in the last five years from the NHMRC, National Foundation for Medical Research Innovation, the Allergy and Immunology Foundation of Australasia, Asthma Australia, Queensland University of Technology, The University of Queensland and a contracted research grant from Stallergenes (France), in-kind provision of materials from ThermoFisher (Sweden) and services from Sullivan Nicolaides Pathology (QLD, Australia). She is a named inventor on a patent assigned to QUT granted in Australia, allowed in USA and three applications pending examination in Australia, USA and Europe. JMD’s institute has received Honorarium payments and travel expenses for education sessions and conference presentations from Stallergenes Australia, GlaxoSmithKliene, Wymedical, and Meda Pharmaceuticals. FT and MH declare no conflicts of interest.
Re: Stormy weather: a retrospective analysis of demand for emergency medical services during epidemic thunderstorm asthma
An important and significant finding during the unprecedented severity thunderstorm asthma event that occurred in Melbourne in November 2016 was the large number of previously asymptomatic and undiagnosed people who actually experienced symptoms but did not require emergency services or hospitalisation.
In as yet unpublished work, more than a third of people surveyed with no past history of asthma experienced symptoms during this event. Although the most frequent was hay fever, asthmatic symptoms were also not infrequently described. Not unexpectedly, in view of the severity of the event, taking preventer medication regularly was found to be insufficient to prevent symptoms, however it is possible that it may have moderated these.
We also noted that apart from treatment escalation with the use of antihistamines, inhaled bronchodilators, and oral steroids, about 5% of those who experienced symptoms on the day also attended their local medical practitioner.
The extreme severity of the thunderstorm asthma event in Melbourne highlights not only the observable extent of stress on a health care system but also the invisible burden and potential impact for the future.
Competing interests: No competing interests