Conventional diagnostic tests (such as radioallergosorbent test [RAST] and skin prick test [SPT]) use native raw pollen allergen extracts to establish allergy. However, recombinant allergens may offer important advantages compared with their natural counterparts.
This study evaluated serum immunoglobulin E (IgE) in patients with grass-induced allergic rhinitis (AR) or AR with asthma (ARA), comparing assays with natural or recombinant grass allergens.
Sixty patients (33 AR, 27 ARA) positive with SPT and serum IgE for Phleum pratense were enrolled in the study. Serum IgE specific for conventional and recombinant Phleum pratense: rPhl p 1, rPhl p 2, nPhl p 4, rPhl 5b, rPhl p 6, rPhl p 7, rPhl p 11, rPhl p 12, were measured by the IFMA procedure (ImmunoCAP, Phadia, Uppsala, Sweden). Data were expressed as the median (md) and percentiles. Recombinant allergen results were expressed also as the percentage of positive concentrations. The Wilcoxon test was used to compare samples. Because diagnosis is a binary variable (AR/ARA), logistic regression analysis was performed to identify possible correlates.
IgE concentrations assessed with recombinant allergens were significantly higher in ARA patients (p = .05) than in AR patients. A value >5.8 kU/L is the optimal cut-off to discriminate AR and ARA patients. Model specificity was 76%, sensitivity 78%, and efficiency 77%.
This study shows that IgEs for natural and recombinant grass pollen allergens are significantly higher in patients with AR and asthma. Moreover, using recombinant allergens it is possible to define a prediction model for diagnosis with 77% efficiency. Therefore, this study may suggest that there are advantages of using recombinant or purified, native allergens over crude extracts.