OBJECTIVES: Continuous exposure to allergens can trigger the development of allergic rhinitis (AR) and asthma. This study estimates the proportion of patients with AR at risk of developing asthma, and how many of those patients have allergen specific diagnoses.

METHODS: The study was performed using The Health Improvement Network (THIN), a UK primary care database. Patients were selected using Read codes indicating a diagnosis of AR, and included if they had at least 12 months medical history prior to AR diagnosis. Patients were excluded if a Read code indicated diagnosis of asthma prior to that of AR. The medical notes of 200 randomly selected patients were examined for the mention of key terms and their misspellings, to identify allergen-specific AR.

RESULTS: The THIN population comprised 13,217,187. In total, 940,259 (7.1%) patients had ever been diagnosed with AR. Of these, 786,727 (83.7%) were registered in THIN for at least 12 months prior to AR diagnosis date. There were 593,471 (75.4%) patients identified as being at risk of developing asthma. Ten of the 200 randomly sampled patients (5.0% (95% confidence interval (CI) 2.7-9.0) had a record of sensitization to any specific allergens included in free text fields, and four (2.0% (95% CI 0.8-5.0)) denoted sensitization to grass pollen.

CONCLUSIONS: A large number of patients with AR are at risk of developing asthma. Only a small proportion of patients with AR at risk of developing asthma, have allergen-specific diagnoses.