Research Article: Retrospective analysis of aeroallergen’s sensitization patterns in Edmonton, Canada

Date Published: February 13, 2019

Publisher: BioMed Central

Author(s): Hanan Ahmed, Maria B. Ospina, Kyriaki Sideri, Harissios Vliagoftis.


Sensitization to common environmental aeroallergens plays a significant role in the pathogenesis and severity of respiratory allergic disorders, specifically asthma and allergic rhinitis. Understanding sensitization patterns helps clinicians tailor care more effectively. This study examines patterns of sensitization to aeroallergens in subjects suspected of having an allergic disease in Edmonton and catchment area.

Retrospective chart review of skin prick test (SPT) results to 11 environmental aeroallergens performed between January 1st and June 30th 2014 at a University-based clinic, where patients are referred for SPT by allergists, respirologists, otolaryngologists, internists and general practitioners. Potential differences in aeroallergen sensitization patterns were evaluated.

A total of 623 patients (36.9% males; 63.1% females), aged 4–84 years (mean age 38.6 years) had SPT done, of which 438 (70.3%) had a positive test for at least one aeroallergen (atopy). There were no significant sex differences in the frequency of atopy (males: 71.3% versus females: 69.7%; p = 0.373). The frequency of sensitivity to particular allergens among atopic subjects was: cat (53.1%), house dust mites (50.3%), grass (39.2%), birch (23.7%), alternaria (23.7%), dog (17.3%), poplar (12.1%), cedar (9.6%), aspergillus (9.6%), hormodendrum (8%), and penicillium (6.2%). Of 438 atopic patients, 110 (25.1%) were mono sensitized, 199 (45.4%) oligosensitized (2–3 allergens), and 129 (29.5%) polysensitized (≥ 4 allergens). There were no significant differences between males and females in the odds of being oligo-sensitized (OR: 0.95; 95% CI 0.58, 1.57). Polysensitization was significantly more frequent in males 37.2% than in females 24.8%; (OR: 0.95; 95% CI 0.58, 1.57).

Cat is the most frequent perennial allergen and timothy grass pollen the most frequent seasonal allergen in Edmonton and catchment area. There was no significant difference in the frequency of atopy between males and females. However, males were more likely to be polysensitized compared to females.

Partial Text

Asthma and allergic rhinitis are common conditions, with significant morbidity and high economic burden on the individual and society [1]. It is estimated that 12% of children, and 8% of adults in Canada suffer from asthma, while 20–25% of Canadians have symptoms of allergic rhinitis [2]. The prevalence of allergic rhinitis continues to rise worldwide. The prevalence of asthma continues to increase in low- and middle-income countries as they develop into more industrialized countries, but is plateauing in developed countries [2, 3].

A total of 627 patients underwent SPT to common environmental aeroallergens. Four patients were excluded from the analysis because of dermographism (1 case) or negative response to histamine (3 cases) leaving a total of 623 SPT results for analysis. The frequency of atopy among age and sex groups is illustrated in Table 1. There was no statistically significant difference in the frequency of atopy between males (71.3%) and females (69.7%) (OR: 0.92; 95% CI 0.64, 1.32). As shown in the table, individuals in the age group ≥ 66 years were the least likely to have positive SPT results (OR: 0.27, 95% CI 0.12, 0.61, p = 0.002, compared to the 19–35 group). All other groups had equal rates of atopy.Table 1The frequency of atopy among age and sex groupsPatient groups according ton (% of total population)% of atopy within the groupSex Female230 (37.7)69.7 Male393 (62.3)71.3Age (years) ≤ 1857 (9.1)70.2 19–35227 (36.4)73.1 36–50181 (29.2)73.5 51–65130 (20.8)66.9 ≥ 6628 (4.5)42.9

More than two-thirds of patients had skin reactivity to at least one aeroallergen. Our study population represents a selected group of patients referred for SPT likely due to a suspicion of allergy, which could explain the higher prevalence of atopy when compared to other Canadian cities (62.7%) [14], and the United States (54.3%) [15]. It is interesting that even in a highly selected population, 29.7% had no evidence of atopy. The absence of significant differences in the frequency of atopy between males and females and decreased likelihood of sensitization with advancing age were similar to the findings reported in other studies [14, 16].

Our study shows that the three most common sensitizing aeroallergens in Edmonton and catchment area are cat, house dust mite and timothy grass. It is encouraging that immunotherapy for all three allergens has been shown to be effective [37–40]. The reason behind the high incidence of sensitization to house dust mites in our study is not understood, since house dust mite levels are expected to be low in Edmonton and surrounding areas. Further studies are needed to better understand the role of house dust mite in the development of allergic diseases in Alberta and similar environments.




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