Intermediate
Technical
In the Industry Vocabulary Test
companion diagnostic
Medical device that identifies patients eligible for specific targeted cancer therapies based on biomarker status.
Full Definition
A laboratory test or assay that is specifically developed and validated to identify patients who are most likely to benefit from a particular targeted therapy or who may experience adverse reactions. Companion diagnostics are typically co-developed with therapeutic agents and are required by regulatory agencies for drug approval and clinical use. In cancer genomics, these tests detect specific genetic alterations, protein expressions, or other biomarkers that predict treatment response to precision medicine approaches.
Usage
Usage note: CDx abbreviation acceptable after first use; emphasizes therapy-linked testing requirement.
In Context
- "The HER2 companion diagnostic is required before initiating trastuzumab therapy in breast cancer patients." — Treatment protocol
- "FDA approval of the targeted therapy included validation of its companion diagnostic assay." — Regulatory submission
Also known as
CDx
companion test
Contrasted with
screening test
prognostic test
Don't confuse with
complementary diagnostic
biomarker test