Relevance of specific IgE antibody titer to the prevalence, severity, and persistence of asthma among 19-year-olds in northern Sweden

Abstract

Background: Although sensitization to indoor allergens is strongly associated with asthma, there are questions as to how this relates to asthma symptoms.

Objective: We sought to study the relevance of IgE antibodies to cat and dog allergens in an area in which (1) the climate discourages cockroach, fungal, and mite growth and (2) dander allergens are known to be present in schools and houses without animals.

Methods: IgE to 8 allergens was tested in 963 sera from a population-based study on 19-year-olds, and associations with asthma symptoms, diagnosis, and treatment were examined. In positive sera IgE to specific cat and dog allergens was also assayed.

Results: IgE specific for animal dander had the highest prevalence and strongest relationship to asthma diagnosis. Furthermore, asthma severity, as judged by the frequency of symptoms and use of treatment, was directly associated with the titer of IgE antibodies to animal dander. Among the 103 subjects who had current asthma at age 19 years, 50 had asthma before age 12 years. Among those 50, the odds ratios for asthma related to any IgE antibodies to animal dander or high-titer IgE antibodies (≥17.5 IU/mL) were 9.2 (95% CI, 4.9-17) and 13 (95% CI, 6.9-25), respectively. In multivariable analysis IgE antibodies to Fel d 1 and Can f 5 were each associated with current asthma.

Conclusion: High-titer IgE antibodies to cat and dog allergens were strongly associated with the diagnosis, severity, and persistence of asthma; however, a large proportion of patients with current asthma did not live in a house with a cat or dog.

Keywords: IgE antibodies; IgE titer; asthma severity; cat ownership; mammalian allergen.

Fig 1

Probability of wheeze related to the titer of IgE antibodies specific for cat dander, dog dander, dust mite, or birch pollen. Unadjusted logistic regression lines are depicted with 95% C.I. in gray. P<0.001, P<0.001, P=0.17, P<0.001, for cat dander, dog dander, dust mite and birch pollen, respectively.

Fig 2

Relationship between IgE antibodies to any mammal and asthma severity assessed by frequency of wheezing attacks [A] or medication usage [B]. The number of subjects in each of the seven groups shown was: 716 negative; and 30, 63, 80, 40, 15, and 19 ≥100 IU/mL. Using chi square test for trend the p value was <0.001 for wheezing attacks or medication usage.

Fig 2

Relationship between IgE antibodies to any mammal and asthma severity assessed by frequency of wheezing attacks [A] or medication usage [B]. The number of subjects in each of the seven groups shown was: 716 negative; and 30, 63, 80, 40, 15, and 19 ≥100 IU/mL. Using chi square test for trend the p value was <0.001 for wheezing attacks or medication usage.

Fig 3

Relationship between sensitization and asthma diagnosis among subjects with persistent asthma (n=68); late onset asthma (n=63), and no reported asthma (n=672) [A]. The same analysis for subjects with current asthma which was persistent (n=50) or late onset (n=38), or no reported asthma (n=672) [B]. For each group the prevalence of sensitization is shown for any allergen (≥0.35 IU/mL), any mammalian allergen, high titer mammalian allergen (≥17.5 IU/mL), or no sensitization.

Fig 4

Relationship between IgG specific for Fel d 1 and cat ownership Both low titer (150–500 Units/mL) and high titer (>500 Units/mL) were significantly high among cat owners (n=279) (**p<0.01). By contrast, any IgE to cat dander was less common among cat owners (*p<0.05). The approximate range of cat allergen exposure is shown for cat owners and non-cat owners (n=684) (See Ref 37).