xT CDx

Companion Diagnostic

xT CDx is an FDA-approved companion diagnostic used to help identify patients who may be eligible for targeted therapies.

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Clinical Use

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Use

xT CDx is an FDA-approved next-generation sequencing (NGS) assay for comprehensive genomic profiling of solid tumors. The test analyzes 648 cancer-related genes to detect substitutions and insertions/deletions (indels), along with microsatellite instability (MSI) status. Using tumor-normal paired sequencing, xT CDx distinguishes somatic alterations from germline variants to provide a high-confidence molecular profile. The test is intended to aid in identifying patients who may benefit from targeted therapies in accordance with approved companion diagnostic indications and established oncology guidelines.

Special Instructions

xT CDx requires submission of both tumor tissue (FFPE) and a matched normal sample (blood or saliva) to enable tumor-normal paired analysis. Testing is performed at Tempus Labs (Chicago, IL). Orders may be submitted via the Tempus Hub, paper requisition, or integrated electronic ordering workflows. In cases where tumor tissue is insufficient, alternative specimen strategies may be considered per laboratory protocols.

Limitations

xT CDx requires FFPE-prepared tumor tissue specimens and matched normal blood or saliva. It is not intended for germline variant reporting. A minimum tumor percentage of 20% is necessary to detect variants, 30% for MSI. The performance is not established for insertions or deletions larger than 25 base pairs. A negative result does not eliminate the possibility of mutations below the detection limit. MSI status is derived from genome-wide analysis, which may not correlate with current guidelines.

Test Details

FDA Approved

Companion Diagnostic