To the Editor:
Severe asthma (SA) affects less than 5% of the pediatric asthma
population but is considered to account for approximately half of total
pediatric asthma healthcare costs. Allergic comorbidities, including
food allergies (FA) and allergic rhinitis (AR), are frequent in children
with SA (1). The presence of FA and AR increases asthma severity (1–6)
and medication use (4–6). Treating AR improves asthma symptoms (3).
However, the economic burden of allergy in children with SA has been
poorly studied. We aimed to determine the economic contribution of
allergy for the French national health insurance (NHI) for the treament
of children with SA at the individual level.
Children with SA, defined as those requiring step 4 or 5 of treatment of
the Global Initiative for Asthma (GINA), regularly followed in the
Department of Pediatric Pulmonology of Necker Hospital were included as
previously described (7). The diagnosis of SA, FA, and AR were made by a
physician according to guidelines (8-10). A physician-guided
questionnaire was completed with parents to assess individual
expenditures related to asthma and allergic comorbidities in the
previous six months. Parental claims were confirmed by analysis of the
medical records. The methods are detailed elsewhere (7). First, we
determinated the direct, indirect, and global costs of SA over a
six-month period (7) and then assessed the allergy-related costs. The
costs related to allergy included anti-allergic medications (oral
antihistamines, steroid nasal sprays, anti-allergic eye drops,
adrenaline autoinjectors, and allergen immunotherapy), anti-IgE
treatment, scheduled ambulatory or hospital outpatient visits to an
allergist, pulmonologist, ophthalmologist, or dermatologist, skin tests,
blood tests for allergy-specific IgE, and day care unit (DCU) admissions
for oral food challenge (OFC) (7). Finally, we compared the economic
burden of allergy between children with SA and those without (NSA) (7).
Parents were informed and accepted to participate in the study. The
local ethical committee confirmed that Institutional Review Board
approval was not required.
Forty-eight children with SA and 26 with NSA were included. Their
general characteristics are summarized in Table 1. The individual global
cost of SA was \euro3,982 (4,422) over the six-month study period
(7). For children with
allergic SA, the cost attributed to allergy was \euro2,803 (3,709),
representing 48.1% (35.2) of the direct SA costs and 45.8% (34.9) of
the global SA costs. Overall, the number of allergic comorbidities for
children with SA weakly correlated with global (r = 0.33, p = 0.02) and
direct SA costs (r = 0.35, p = 0.01). The global and direct costs of SA
were higher for children with allergic comorbidities than for those
without (\euro4,646 (4,635) vs. \euro1,107 (1,173), p = 0.02;
respectively). However, these figures partially reflect the actual
economic contribution of allergy in children with allergic SA. For those
requiring omalizumab, the economic burden of allergy was \euro5,057
(3,809) representing 74.1% (24.4) of direct SA costs and 71.6% (24.3)
of global SA costs. In this group, omalizumab was the main driver of
costs, representing 73.6% of direct SA costs and 71.5% of global SA
costs. For children with allergic SA not requiring omalizumab, the
economic burden of allergy was \euro174.50 (289.7), representing
17.8% (16.1) of direct SA costs and 15.8% (15.9) of global SA costs.
Regardless of omalizumab use, the economic burden of allergy was similar
among children with allergic SA (\euro153.3 (159.4) vs \euro174.50
(289.7), p = 0.99). However, the burden of allergy expressed as a
percentage of direct and global SA costs was lower for children with SA
requiring omalizumab than those who did not (3% (4.2) vs. 17.8%
(16.1), p < 0.01 and 2.9% (4.2) vs. 15.8% (15.9), p
< 0.01, respectively).
Global, direct, and indirect costs did not differ between children with
NSA, with or without allergic comorbidity (Table 3). For children with
allergic NSA, the cost of allergy was \euro134.40 (213.90),
representing 40.8% (33.3) of the asthma direct costs and 34.7 % (32.2)
of the asthma global costs. Thus, regardless of omalizumab use, the cost
of allergy for children with allergic SA and that for those with
allergic NSA was similar (\euro163.1 (225.9) vs . \euro134.40
(213.9) (p = 0.19). However, the economic burden of allergy was greater
for children with NSA than those with SA: 40.8% vs 9.8% of direct
costs and 34.7% vs. 8.9% of global costs, respectively (both p
< 0.01). Finally, the economic burden of allergy was similar
between children with allergic SA not requiring omalizumab and those
with allergic NSA (\euro174.5 (289.7 vs. \euro134.4 (213.9), p =
0.29).
This study shows that the costs attributed to allergy for children with
SA are substantial and mostly driven by omalizumab, but are minor when
omalizumab is not taken into account. The economic burden of allergy was
similar between children with allergic SA not requiring omalizumab and
those with allergic NSA, suggesting a low cost-effectiveness ratio, at
least in the latter group. The global and direct costs of children with
allergic SA were higher than those of children with non-allergic SA.
This finding confirms that the presence of allergic comorbidities
increases the costs of asthma management (11) and supports that allergy
is associated with asthma severity. Our study had several limitations.
Only a small number of children were included. However, we included
children with well-defined doctor-confirmed SA, with and without
omalizumab, reflecting the heterogenity of this population. In addition,
our study was performed in a tertiary-care center. Thus the children
with NSA may not be representative of community children. Our estimation
was based on parental declarations, with a potential memory bias and a
risk of misestimation of certain expenditures. We limited this risk by
analyzing the medical records, which confirmed the parental claims. The
best design would have been to obtain the data of children selected by a
physician from the NHI. However, this approach is rarelly authorized in
France. Moreover, the study covered a short period of time including
winter and two months of spring, which may lead to underestimation of
costs related to seasonal allergy treatments. In addition, the number of
children under allergen immunotherapy was small (1 in the group of
children with allergic SA vs. 4 children with allergic NSA (p = 0.03)).
In summary, this study is the first to precisely analyse the proportion
of costs attributed to allergy in pediatric SA. As expected,
allergy-related costs are mainly driven by omalizumab. However, for
children with allergic SA who do not require omalizumab, the economic
contribution of allergy to SA costs is relatively small, suggesting a
low cost-effectiveness ratio.