Development of a symptom load index: enabling temporal and regional pollen season comparisons and pointing out the need for personalized pollen information

This study describes the development of an index, the symptom load index, to compare the severity of pollen seasons for pollen allergy sufferers during different seasons in different geographical regions. This is done by comparing symptom data with pollen data. This study is based on symptom data of the Patients' Hayfever Diary (PHD) and on pollen data from the European Aeroallergen Network (EAN). The PHD allows objective assessment of the season severity. Season length calculated on the basis of pollen data from the EAN and all records of users in a specific region are included in calculation of the symptom load index. It is thus not influenced by pollen counts during the season. Its application to pollen seasons of the three important pollen types birch, grass and ragweed in Austria and Germany from 2009 to 2013 proved that the impact of a pollen season on allergy sufferers is not correlated with total pollen loads. The possibility to calculate the pollen season in the allergy sufferers' point of view is a novelty that inaugurates new pathways for the future of pollen information. Furthermore, such an index will be of value for the establishment of personalized pollen information and for calculations of pollen thresholds.