Flow-Cytometric Cellular Allergen Stimulation Test in Latex Allergy

Background: The use of flow-cytometric basophil activation to different allergens has been recommended in recent years. In this study, we analyzed the diagnostic reliability of the flow-cytometric allergen stimulation test (FAST) after latex-specific stimulation in vitro. The diagnostic reliability of the technique was assessed as well as its correlation with other in vitro diagnostic parameters. Methods: 43 patients allergic to latex with a positive history and skin test participated in the study. Thirty subjects (20 of them exposed to latex) with a negative history, skin tests and serum-specific IgE determination to latex were used as controls. In FAST the percentage of basophils that express CD63 as an activation marker after in vitro stimulation with allergen (latex) is determined by flow cytometry, following double labelling with the monoclonal antibodies anti-CD63-PE and anti-IgE FITC. Results: Intraclass correlation coefficient in FAST with latex was 0.995 (p < 0.0001), which demonstrates the excellent reproducibility of this technique. Taking a cutoff point of 10% by means of ROC curves, FAST yields a sensitivity of 93% and a specificity of 100%. The FAST positive predictive value in latex allergy was 100% and the negative predictive value was 99.9%. We found a positive and significant correlation between FAST and specific IgE (CAP) with the histamine release test and specific sulphidoleukotriene production [cellular allergen stimulation test (CAST); p < 0.05]. Conclusions: FAST is a highly reliable technique (93% sensitivity and 100% specificity) in the in vitro diagnosis of IgE-mediated latex allergy.