FACTORS ASSOCIATED WITH IMPROVED CLINICAL CONTROL IN A DIFFICULT-TO-TREAT PAEDIATRIC ASTHMA COHORT THROUGH THE COVID-19 PANDEMIC LOCKDOWN PERIOD.

It is recognised that fewer children attended Emergency Departments (ED) with asthma exacerbations during the COVID-19 pandemic.1,2 However, it is unclear why. The common triggers of asthma attacks include viral infections, high pollen counts and air pollution. It would seem likely that significant changes in one of more of these would impact on asthma control. There have been no reports, to our knowledge, examining asthma control and medication adherence in a paediatric difficult to treat (DTA) asthma cohort over this period, and comparing it with air pollution and respiratory viral data. The clinical course of, and external influences upon, the Northern Irish paediatric DTA cohort through the pandemic can inform this discussion. The UK Government recommended that children with severe asthma should ‘shield’ from COVID-19 infection.3 To determine if there was evidence of a significant difference from the previous year, the clinical course of the DTA cohort of 51 patients through the epoch February-May 2020 was compared with the corresponding epoch in 2019. Unscheduled care attendances, courses of rescue oral corticosteroids (OCS), a marker of medication adherence (repeat prescriptions), and Asthma Control Test (ACT) scores for the DTA cohort were compared (Table 1). Levels of airborne aeroallergens, air pollution data and prevailing respiratory viruses over the two epochs were also compared.

Table 1

Comparison of factors associated with asthma control for the Northern Irish paediatric DTA cohort between corresponding epochs in 2019 and 2020. Air pollution and pollen levels refer to daily levels measured in Belfast over the specified epoch

	1st Feb-31st May 2019	1st Feb-31st May 2020	p-value
PM10 (μg/m3)	16·4 (10·6)	13 (5·6)	<0·01
PM2.5 (μg/m3)	52·5 (24)	31·1 (12·9)	<0·01
SO2 (μg/m3)	4·3 (2·2)	1·3 (0·6)	<0·01
NO2 (μg/m3)	11 (4·9)	10·9 (7·8)	0·9
Plane tree pollen (grains/m3)	0·4 (1·5)	0·01 (0·1)	0·01
Hazel tree pollen (grains/m3)	1·1 (2·2)	0·4 (1)	<0·01
Ash tree pollen (grains/m3)	2·2 (4·6)	10 (23·3)	<0·01
Grass pollen (grains/m3)	0·4 (1·4)	2·3 (6·8)	0·04
Unscheduled care attendances /per patient*	0 (0,1)	0 (0,0)	0·01
ACT score (out of 25)*	17 (12,19)	20 (15,24)	<0·01
Number of courses of oral steroids/ per patient*	0 (0,1)	0(0,0)	0·01
Adherence (% collections of ICS prescriptions)*	100 (60,100)	100 (50,100)	0·6

Data are presented as Mean (SD) unless indicated.

Median (IQR). Statistical tests used: Student t-tests and Wilcoxon rank-sum tests for non-parametric data. A p-value ≤0.05 indicated statistical significance.

ICS: Inhaled corticosteroids; ACT: Asthma Control Test; NO2: Nitrogen dioxide; PM10: Particulate matter less than 10 μm in diameter; PM2.5: Particulate matter less than 2·5 μm in diameter; SO2: Sulphur Dioxide.

Unscheduled care attendance data suggested that the cohort presented significantly less to emergency services and received fewer courses of rescue OCS during the pandemic than in 2019. ACT data was better for the 2020 epoch, suggesting that these differences may be on the basis of improved asthma control. No difference in inhaler adherence was observed. This may represent a ‘ceiling effect’, as suboptimal adherence is improved and reinforced with remote monitoring at our DTA clinic.4 Respiratory viral data showed that the number of samples of secretions positive for rhinovirus in 2020, as a percentage of the total number of positive samples, was less than half of that for 2019 [total positive samples: 9940 in 2019 and 12645 in 2020 - and rhinovirus positive samples: 428 (4·3%) v 234 (1·9%)]. There was no consistent pattern for tree pollen levels but there were greater levels of grass pollen in 2020. Air pollution data showed significantly lower levels of atmospheric PM2.5, PM10 and SO2 (but not NO2) during the 2020 epoch.

This data suggests that shielding has been protective through the pandemic, leading to improved asthma control. The viral data may reflect the restricted movement of children, thereby limiting viral spread. Less air pollution is also likely a contributor to fewer exacerbations. Although there were greater airborne grass pollen levels in 2020, children may have been protected from outdoor exposure as a result of shielding indoors.

Once shielding stopped, children were mixing much more, resulting in greater exposure to respiratory viruses. However, schools have tried to implement measures to maintain social distancing and attenuate viral spread. It remains extremely important to optimise adherence, inhaler technique and the use of asthma plans over this period of uncertainty to help to minimise asthma morbidity.