Diagnosis of cypress pollen allergy: in vivo and in vitro standardization of a Juniperus ashei pollen extract

Background: Cypress pollen allergy is a major cause of rhinoconjunctivitis and asthma in the Mediterranean area. The nonstandardized cypress allergen extracts currently available for the diagnosis of cypress allergy have a low level of activity. The search for an active material has led to the selection of Juniperus ashei (Ja) pollen because of its very high cross‐reactivity with cypress extracts and its superior allergenic activity. The aim of this study was to characterize in vitro and calibrate in vivo an in‐house reference extract (IHRS) of J. ashei pollen and determine the specificity and sensitivity of a standardized Ja extract for the prick test diagnosis of cypress allergy. Methods: Juniperus ashei pollen extract was analysed by 2‐D electrophoresis. The IHRS Ja extract was calibrated by skin prick testing in 28 cypress‐allergic patients. The sensitivity and specificity of cypress allergy diagnosis using a standardized Ja extract was studied by skin prick test in 42 cypress‐allergic patients and 53 nonallergic patients. Jun a 1 content of the IHRS was determined by a monoclonal antibody‐based electrophoretic technique. Results: The Jun a 1 content of the 100 IR/ml Ja IHRS extract was 180 μg/ml. For in vivo diagnosis of cypress allergy, Ja pollen extract demonstrated a sensitivity of 95%, a specificity of 100%, a negative predictive value of 96%, and a positive predictive value of 100%. Conclusion: Standardized Ja pollen extract is therefore a very appropriate tool for the in vivo diagnosis of cypress pollen allergy and good candidate for specific immunotherapy.