Diagnostic biologique de l'allergie respiratoire : évaluation du réactif Vidas Stallergy genévrier dans l'allergie au cyprès

Cypress allergy is an important health issue in Mediterranean areas but its diagnosis is still difficult in some cases. The fact that cypress and juniper tree pollens share a number of allergens, together with the higher allergenic protein contents of the latter have recently led allergologists to use juniper pollen extracts while testing for cypress allergy. In the present study we have evaluated a new Vidas bioMérieux reagent, Stallergy ST6, designed for the detection and quantification of anti-juniper serum IgE, when applied to cypress allergy diagnosis. In thirty-one Respiratory Diseases Department outpatients clinically suspected of cypress pollen allergy, Stallergy ST6 results were compared to those of prick tests and of serum IgE quantification using the CAP System (Phadia). There is a good class concordance between IgE results yielded by the two methods. We conclude that Stallergy ST6 provides a sensitive and specific reagent for cypress allergy diagnosis.     

Mise au point d'un dosage automatisé des IgE spécifiques des allergènes des pollens de cyprès et de genévrier par VIDAS Stallergy

Study objective

Cypress pollen is a significant cause of allergies in the Mediterranean area. In order to improve the in vitro diagnosis to cypress sensitization, we used a Juniperus ashei extract to develop a new semi-quantitative test for the measurement of IgE specific to juniper and cypress pollen allergens based on the VIDAS automated system.

Methods

The VIDAS Stallergy^® assay combines a two-step enzyme immunoassay sandwich method with a final fluorescence detection. The reagent comprises the Solid Phase Receptacle (SPR) coated with a J. ashei extract, which serves as a solid phase as well as a pipetting device during the assay and a strip that contains all the ready-to-use reagents.

Results

The precision study shows coefficients of variation lower than 1.7% for intra-assay variability and between 1.6 and 9.5 for inter assays variability. Correlation with the CAP system^® method shows an 80.7% agreement to the nearest class (N = 57). For 65% of sera class results are similar with the two techniques, and for 33% of sera, class results are higher with the VIDAS method. Test specificity is confirmed by VIDAS inhibition experiments. A sensitivity study performed using 82 clinically recognized cypress allergic patients shows that 97.6% of the patients are detected with the VIDAS Stallergy^® Juniper reagent.

Conclusion

The Juniper Stallergy^® test allows to measure specific IgEs to cypress pollen, with a sensitivity of detection at least similar to the CAP system^® method.