Claudin 18 (CLDN18) (43-14A) Test

Available through our international laboratory collaboration with Mayo Clinic Laboratories

Overview

The Claudin 18 (CLDN18) (43-14A) test is a semi-quantitative immunohistochemistry (IHC) assay, performed manually, to evaluate the presence and expression level of Claudin 18 protein in tissue specimens.

Claudin 18 is a tight junction protein expressed in the gastric mucosa and certain tumors, particularly:

• Gastric adenocarcinomas
• Gastroesophageal junction cancers

It has emerging significance as a predictive biomarker for targeted therapy selection — notably for anti-CLDN18.2 monoclonal antibody treatments (e.g., zolbetuximab).

Clinical Utility

This test aids in:

• Identifying CLDN18.2 expression in gastric and gastroesophageal junction adenocarcinomas.
• Stratifying patients for potential eligibility for targeted therapy.
• Providing semi-quantitative scoring of protein expression to guide clinical decision-making.

Specimen Requirements

• Specimen Type: Formalin-fixed, paraffin-embedded (FFPE) tissue block or unstained slides from tumor tissue.
• Preferred Source: Primary tumor or metastatic site.
• Number of Slides: As per testing protocol (typically 1–2 unstained slides at 4–5 μm thickness).

Clinical Background

CLDN18.2 is a promising therapeutic target in gastric and gastroesophageal cancers.

• Overexpression has been linked to tumor progression.
• May predict response to specific monoclonal antibody treatments.
• The semi-quantitative IHC method provides precise, reproducible results, helping oncologists identify candidates for precision oncology approaches.

Turnaround Time

• Estimated: Typically within 2–4 business days from receipt at the reference laboratory.

Advantages of the Claudin 18 (CLDN18) (43-14A) Test

• Enables personalized cancer treatment planning
• Performed by a world-class reference pathology team
• High specificity for CLDN18.2 detection
• Supports clinical trial and targeted therapy eligibility assessment

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