Double sensitization
Patients were identified that had IgE tests done for birch and ash extract, as well as their major allergens Bet v 1 and Ole e 1. Extract-double-sensitized patients (=positive for birch and ash extract) were grouped by their major-allergens (Bet v 1 pos. + Ole e 1 pos., Bet v 1 pos. + Ole e 1 neg., Bet v 1 neg. + Ole e 1 pos., Bet v 1 neg. + Ole e 1 neg.) to see if extract-positivity was caused by cross-reaction or if there was a relevant sensitization to both major allergens.
The same analysis was performed for patients with available IgE tests for mugwort and ragweed extract as well as their major allergens Art v 1 and Amb a 1.