Diagnostic procedures using natural extracts show only limited quantitative correlation between in vivo and in vitro results. Highly pure recombinant allergens might show more predictive findings. In this study the extracts of birch pollen (BPE) and mugwort pollen (MPE) were compared with their recombinant major allergens rBet v1 and rArt v1.

34 patients allergic to BP and 32 patients allergic to MP and in addition 5 healthy subjects were investigated. SPT and NPT were performed with the natural extracts (BPE/MPE) and the according recombinant allergens rBet v 1 and rArt v 1 at 1, 10 and 100 mg/ml. Specific serum IgE was measured by the Pharmacia CAP system (t3, t215, w6) or ELISA (Art v 1).

BPE and rBetv1 were able to elicit similar allergic reactions in vivo and specific IgE binding in BP allergic patients. The sensitivity of BPE in NPT was higher compared to rBetv1 and higher amounts of rBet v 1 were needed for NPT than for skin tests to cause allergic reactions. MPE showed higher sensitivity in patients allergic to mugwort compared to r Art v 1 in SPT and in vitro. The reactivity of rArt v 1 in NPT was even significantly lower compared with MPE and natural Art v 1.

Both recombinant allergens induced allergic reaction in the respective patients. However reactivity in NPT with rAllergens compared with the extract can substantially vary and may also only show limited correlation with SPT and specific IgE.