Background: Alternaria alternata is a risk factor for developing asthma. Alt a 1, which has been described as the major allergen in A alternata, shows a good correlation with A alternata spores only when they have germinated.

Objectives: The objective of this study was to determine the correlation between spore counts and clinical symptoms in patients with allergic asthma and/or rhinitis monosensitized to A alternata.

Methods: Two types of samplers were used to determine exposure: a Burkard spore trap to collect A alternata spores and a high-volume air sampler to collect airborne particles. A total of 366 air filters were collected. Alt a 1 levels were measured by monoclonal antibody-based enzyme-linked immunosorbent assay. Eighteen monosensitized patients were asked to record their daily symptoms throughout the year.

Results: A alternata spores were detected throughout the year, whereas Alt a 1 was detected only between March and December. Symptoms showed positive and signifi cant correlations with spore counts (r=0.459, P<.001), and Alt a 1 levels (r=0.294, P<.001). The correlation between spores and Alt a 1 was low. The negative binomial model proved that an increase of 10 pg/m3 in Alt a 1 levels increased the number of symptoms at a 3-day lag by 5%.

Conclusions: In patients who are allergic to A alternata, Alt a 1 levels can be considered an important marker for predicting the risk of respiratory symptoms.

Key words: Alternaria alternata. Alt a 1. Allergens. Rhinitis. Asthma.