CDx
Pronunciation: see-D-X
Also written as: CDx — Companion Diagnostic
Companion Diagnostic, an FDA-approved test required for specific targeted therapy patient selection.
Full Definition
CDx (Companion Diagnostic) refers to a medical device or test that provides information essential for the safe and effective use of a corresponding therapeutic product. CDx assays are co-developed with drugs and undergo rigorous FDA approval processes to ensure analytical and clinical validity. These tests identify patients who are most likely to benefit from a particular therapy or experience adverse reactions. Editors must understand that CDx designation requires specific regulatory approval and differs from laboratory-developed tests (LDTs) or research use only (RUO) assays in terms of clinical utility and regulatory oversight.
Usage
Usage note: Capitalize as CDx (not cdx or CDX). Distinguish from general diagnostic tests by emphasizing regulatory approval status.
In Context
- "The FoundationOne CDx assay identified actionable mutations warranting targeted therapy consideration." — precision oncology report
- "CDx testing confirmed EGFR exon 19 deletion, supporting osimertinib treatment recommendation." — molecular tumor board summary