Towards an Optimal Decision Threshold for Specific IgE to rCan s 3 the Non-Specific Lipid Transfer Protein of Cannabis sativa.

Background: Cannabis allergy is increasingly reported, with Can s 3 as a major allergen. Investigations into sensitisation to Can s 3 utilise sophisticated techniques, including the cytometric bead assay and the basophil activation test. This study aims to utilise a fluorescence enzyme immunoassay to quantify sIgE to Can s 3, employing a recombinant Can s 3 protein.

Methods: This study included 104 cannabis allergic patients, 20 healthy controls and 70 exposed atopic controls. Specific IgE by a fluorescence enzyme immunoassay or cytometric bead assay and the basophil activation test all used the same recombinant allergen. Two-graph ROC curves were used to determine the clinically validated allergen-specific cut-off for maximal sensitivity and specificity and to facilitate direct comparison of the test performances.

Results: Twenty-two individuals were non-responding in the basophil activation test and were excluded from all analyses involving basophil activation test results. The clinically validated cut-off points are > 0.16 kU_A/L, ≥ 0.14 kU_A/L and > 5% for a fluorescence enzyme immunoassay, cytometric bead assay and basophil activation test, respectively. Utilising these thresholds, the fluorescence enzyme immunoassay exhibited a sensitivity of 72% and specificity of 74%, the cytometric bead assay demonstrated a sensitivity of 49% and specificity of 89%. In responders, the basophil activation test exhibited a sensitivity of 51% and specificity of 82%. Remarkably, low positive fluorescence enzyme immunoassay results, particularly below 0.35 kU_A/L, are negative for both cytometric bead assay and basophil activation test. Conversely, utilising the conventional threshold of > 0.35 kU_A/L, the sIgE a fluorescence enzyme immunoassay results exhibited greater congruence with those of the cytometric bead assay and basophil activation test.

Conclusion: This study underscores the complexity of establishing an optimal decision threshold for the sIgE rCan s 3 fluorescence enzyme immunoassay and indicates that the clinically validated decision cut-off may not always represent the most efficacious approach.