Biomarker: C007-IgE Cefaclor

Overview

C007-IgE Cefaclor measures serum IgE antibodies specific to cefaclor, a second-generation cephalosporin antibiotic. Cefaclor-specific IgE is associated with immediate, potentially IgE-mediated hypersensitivity reactions, including urticaria, angioedema, and anaphylaxis. Detectable levels may support a diagnosis of immediate cefaclor allergy, while low or undetectable levels do not completely exclude allergy because some reactions are non-IgE mediated. The test can assist allergy evaluation when interpreted with the clinical history and, when appropriate, skin testing or supervised drug provocation testing.

Clinical Use Cases

Evaluation of suspected immediate hypersensitivity to cefaclor.
Assessment of patients with urticaria, angioedema, or anaphylaxis occurring soon after cefaclor exposure.
Supporting identification of cefaclor as the causative drug when multiple medications were taken.
Allergy evaluation when skin testing or drug provocation testing is unsuitable or carries substantial risk.
Research on IgE-mediated mechanisms and diagnostic performance in cefaclor hypersensitivity.

Specimen Types

Serum obtained from venous blood.
Plasma may be accepted by some assay systems, depending on the laboratory’s validated specimen requirements.

Measurement Methods

Fluorescence enzyme immunoassay for serum cefaclor-specific IgE, including ImmunoCAP-based testing.
Enzyme-linked immunosorbent assay using cefaclor-protein conjugates, primarily in research settings.
Results are commonly reported in kU/L or kUA/L.
Skin testing and basophil activation testing are complementary allergy investigations, not measurements of serum cefaclor-specific IgE.

Test Preparation and Influencing Factors

Fasting is generally not required for serum-specific IgE testing.
Collection should be interpreted in relation to the suspected reaction and the timing of cefaclor exposure.
Cefaclor-specific IgE may become less detectable as the interval from the reaction increases, although persistence for several years has been reported.
Antihistamines generally do not affect the serum IgE measurement, unlike their effect on some skin tests.
A positive result indicates sensitization and does not independently establish clinical allergy.
A negative or low result does not exclude cefaclor hypersensitivity because some immediate reactions may involve non-IgE-mediated basophil or mast-cell activation.
Reported thresholds vary by assay and clinical purpose. One clinical study identified (0.11\ \text{kU/L}) as a useful threshold for immediate hypersensitivity and (0.44\ \text{kU/L}) for distinguishing anaphylaxis among cefaclor-hypersensitive patients, but these values require clinical interpretation and are not universal diagnostic standards.
Recent severe reactions, total IgE concentration, cross-reactivity with other beta-lactams, and assay-specific characteristics may influence interpretation.