Biomarker: T017-IgE Japanese Cedar

Overview

Japanese cedar-specific IgE measures immunoglobulin E antibodies directed against allergens from Japanese cedar (Cryptomeria japonica) pollen. IgE is an immune antibody involved in immediate-type allergic responses. Detectable or elevated Japanese cedar-specific IgE indicates sensitization, but it does not by itself establish symptomatic Japanese cedar pollinosis, which requires correlation with exposure-related clinical history. The test is clinically useful for supporting evaluation of seasonal allergic rhinitis and conjunctivitis, particularly when identifying the relevant pollen allergen is important for management or immunotherapy decisions.

Clinical Use Cases

Supporting the evaluation of suspected Japanese cedar pollinosis, including seasonal allergic rhinitis and allergic conjunctivitis.
Identifying sensitization to Japanese cedar pollen in patients with pollen-related symptoms.
Helping distinguish Japanese cedar sensitization from sensitization to other aeroallergens, such as Japanese cypress, grasses, or mites.
Supporting selection of allergens for allergen immunotherapy when findings are consistent with the clinical history.
Assessing Japanese cedar sensitization in epidemiologic and clinical research.
Monitoring allergen-specific IgE as an outcome measure in selected immunotherapy studies, although changes in IgE should not be interpreted as a direct measure of symptom control.

Specimen Types

Serum or plasma from venous blood, the usual specimen for laboratory measurement.
Nasal secretions, used mainly in research settings to assess local Japanese cedar-specific IgE.

Measurement Methods

Fluorescence enzyme immunoassay, including CAP-FEIA and clinically applied fluorescence-enzyme immunoassays.
Immunoassays using Japanese cedar pollen extract bound to a solid phase.
Enzyme-linked immunosorbent assay, used primarily in research applications.
Radioallergosorbent-type assays, including older RAST methods, although modern nonisotopic immunoassays are more commonly used.
Results may be reported as ( \mathrm{kU_A/L} ), ( \mathrm{UA/mL} ), or an assay-specific class or grade. Reference ranges and positivity thresholds vary by method and laboratory.

Test Preparation and Influencing Factors

Fasting is generally not required for an allergen-specific IgE blood test.
Patients should report all medications and supplements. Some allergy medications, particularly antihistamines, may need to be withheld for certain allergy tests, but medications should not be stopped without clinician instruction.
Serum-specific IgE testing is generally less affected by antihistamines than skin-prick testing, because it measures antibodies in the blood rather than the immediate skin response.
Results should be interpreted with the timing and intensity of Japanese cedar pollen exposure, particularly during the local pollen season.
Age, geographic exposure, degree of pollen exposure, and co-sensitization to other allergens may influence measured levels and clinical relevance.
A positive result indicates sensitization and does not necessarily indicate clinical allergy or predict symptom severity. Interpretation should incorporate symptoms during exposure and other clinical findings.
Assay platforms, allergen extracts, reporting units, and laboratory cutoffs are not fully interchangeable. Results from different methods should be compared cautiously.