Allergic rhinitis (AR) has a considerable impact on patients’ daily functioning and significantly restricts their quality of life. Allergen immunotherapy (AIT) is the only causal option to significantly reduce the severity of symptoms and at the same time prevent complications. Over a period of 18 years, Danish doctors investigated the effectiveness of AIT in the treatment of allergic rhinitis.
In most cases, AR symptoms are caused by IgE-mediated hypersensitivity to plant pollen and are therefore triggered during the pollen season. Allergen immunotherapy with sublingual or subcutaneous repeated administration of large quantities of the triggering pollen allergen is the only treatment that has been proven to have a disease-modifying effect and a long-term effect. However, as it can take months or years for AIT to relieve symptoms, most AR patients rely on faster-acting medications, such as nasal sprays with corticosteroids or antihistamines, oral antihistamines and eye drops.
To investigate the long-term effects of AIT, Dr. Peter Bager and his colleagues from the Department of Epidemiology Research, Statens Serum Institut, Copenhagen, Denmark, conducted a cohort study using nationwide registry data. In a cohort of 1.1 million users of intranasal corticosteroid sprays (representing AR), they compared users treated with grass, birch or mugwort AIT versus non-treated users in terms of baseline year and 24 characteristics in the three years before baseline. The primary outcome was the odds ratio (OR) for the use of an anti-allergic nasal spray during the pollen season in the treated vs. the non-treated group, broken down by years since the start of the study. Finally, 7760 people with AR were included in the study (4373 grass allergy sufferers, 1374 birch allergy sufferers, 60 mugwort allergy sufferers and 2134 with a combination of the 3 AITs). Each person treated with pollen AIT was compared with two non-treated persons, resulting in a sample of 15,520 non-treated persons with AR.
AIT patients are more likely to stop using the nasal spray
In the 7760 AR patients treated with pollen AIT, the OR of using a nasal spray was reduced up to 5 years after the start of the study compared to the 15 520 non-treated AR patients. The probability of having to use a spray was particularly low in the first two years of AIT treatment (0-2 years: OR 0.84 [0,81–0,88]; 3-5 years: OR 0.88 [0,84–0,92]). From the sixth year onwards, however, the OR increased again, the groups became similar and after 10 to 18 years after starting treatment, AIT patients even needed nasal sprays more frequently than untreated people (6-9 years: OR 1.03 [0,97–1,08]; 10-18 years: OR 1.18 [1,11–1,26]). In post-hoc analyses, the results were more consistent in those patients who had already undergone 3 years of hyposensitization and in patients who used a nasal spray in the last pollen season (0-2 years: OR 0.76 [0,72–0,79]3-5 years: OR 0.86 [0,81–0,93]6-9 years: OR 0.94 [0,87–1,02]10-18 years: OR 0.94 [0,86–1,04]) vs. no such application.
The two secondary outcomes use of oral antihistamines (at least one tablet pack) and antiallergic eye drops (at least one container) were defined in a similar way to the primary outcome use of at least one tablet pack. a nasal spray during the pollen season. Patients who received higher levels of pollen AIT in routine care stopped using antiallergic nasal sprays 0-5 years after starting three years of hyposensitization, but not beyond 5 years. According to the authors, this could be due to the fact that patients without AIT used their sprays continuously, while the pause in AIT patients could have an impact on the effectiveness of the AIT. Post-hoc analyses showed that efficacy was more consistent in patients with persistent AR.
For the secondary endpoint use of eye drops, the results of the main analysis were similar. For the secondary endpoint of the use of oral antihistamines, however, the proportion of users in the pollen AIT group was consistently higher than in the non-treated group (0-2 years: OR 1.24, 95% CI 1.18-1.29; 3-5 years: OR 1.19, 95% CI 1.14-1.25). This result was even more pronounced after six or more years (6-9 years: OR 1.29, 95% CI 1.23-1.36; 10-18 years: OR 1.44, 95% CI 1.35-1.54), although the two groups were similar in terms of pre-treatment use.
Lack of data on sensitization status
The use of AR drugs can only be used as a proxy for the severity and persistence of symptoms, the authors explain. However, because the national registry data included 1.1 million people with AR (users of intranasal corticosteroid sprays, INS) available for matching, they were able to match in detail both the number of packs used in the three pollen seasons before baseline (representing the severity or intensity of AR) and in which of the three pollen seasons the medication was used (representing the persistence of AR). This was possible for each specific AR drug.
However, the limitations of the study included a lack of data on the clinical diagnosis of AR and the sensitization status, explain Dr. Bager and colleagues. However, to identify AR patients, the analysis was limited to INS users. In addition, the researchers expected the pollen AIT group to have an AR diagnosis with moderate to severe symptoms and a confirmed sensitization status, as this is a prerequisite for therapy. In the untreated group, misclassification of the AR cannot be ruled out. However, the intake of AR medication in the three years before baseline (including INS) was compared in detail with that of the pollen-AIT patients.
The longitudinal study over 18 years showed that patients in routine care who received pollen AIT had a lower consumption of nasal inhalation medication in the first 5 years after starting pollen AIT compared to patients who did not receive AIT, but not beyond the 5-year period, the Danish researchers summarize.
Literature:
- Bager P, Poulsen G, Wohlfahrt J, Melbye M: The effectiveness of pollen allergen immunotherapy on allergic rhinitis over 18 years: A national cohort study in Denmark. Allergy 2024; 79: 1028-1041; doi: 10.1111/all.16026.
InFo PNEUMOLOGY & ALLERGOLOGY 2024; 6(2): 22-24
