Quest Diagnostics Z Code Identifier User Guide

Quest Diagnostics Z Code Identifier User Guide

What is a Z-Code™ Identifier?
A Z-Code Identifier is a unique 5-character alpha-numeric code associated with certain molecular diagnostics (MDx) tests and is used by certain payers as an adjunct to non-specific CPT codes.
This code is assigned within the Palmetto GBA’s DEX™ Diagnostics Exchange based on the uniqueness of each test being registered. This code, submitted on a claim, in addition to the CPT code, provides greater clarity to help ensure that both payers and providers clearly understand which test is being ordered, performed, and billed.
Why do I need a Z-Code Identifier?
Tremendous growth in molecular and genetic testing provides a great opportunity to improve quality of care. However, there are more choices than ever before, and current molecular CPT codes do not consistently and uniquely identify tests. The Z-Code Identifier helps provide granularity so that all parties know exactly what test was performed in order to know what they are paying for. A growing number of payers will not process a claim if the Z-Code Identifier does not accompany the CPT code on the claim.
What is the Palmetto GBA DEX Diagnostics Exchange?
The DEX Diagnostics Exchange is a molecular diagnostic (MDx) test identification and policy management solution that connects payers and labs to bring clarity to MDx testing. MDx tests are uniquely identified and cataloged using unique DEX Z-Code Identifiers. Some private health plans are beginning to require the “Z” code identifier with their claims. The test registry includes detailed information about MDx tests and the labs that perform them. The test registry catalog is available for reference and review by other stakeholders in the healthcare system. (with Quest’s permission).
What is DEX?
DEX is the acronym used by Palmetto GBA for its Diagnostics Exchange and refers to the database of unique Z-Code identifiers.
Do all payers require Z-Codes™?
No, not all payers require Z-Codes at this time. Currently (Feb. 2026), the following payers require a Z-Code Identifier with certain claims:
● JM A/B (N.C., S.C., Va., WVa.) and JJ A/B (Tenn., Ga., Ala.) administered by Palmetto GBA
● JE A/B (American Samoa, Calif., Guam, Hawaii, Nev., North Marina Islands) and JF A/B (Alaska, Ariz., Idaho, Mont., N.D., Ore., S.D., Utah, Wash., Wyo.) administered by Noridian Healthcare Solutions.

● J5 A/B (Iowa, Mo., Kan., Neb.) and J8 A/B (Mich., Ind.) administered by WPS Government Health Administrators.

● J15 A/B (Ky., Ohio) administered by CGS Administrators, LLC.

● For more information and directions pertaining to the MolDX program, please visit their webсайт на www.PalmettoGBA.com/MolDX

The following payers have been members of DEX, but are currently inactive and do not require a Z-Code Identifier on their claims:
• BCBS of Massachusetts
• Independent Health
• Paramount

Other payers participating with DEX (requirements may vary):
• Medical Mutual of Ohio
• Fallon Health
• Blue Cross® and Blue Shield® of North Carolina
• Community Health Plan of Washington
• MVP® Health Care
Which tests need a Z-Code?
Tests that are billed with specified CPT codes. CPT codes may vary slightly for each payer. In general, tests billed using the following CPT codes will require a Z-Code:
Does the Z-Code process include coverage determinations?
No, the Z-Code identifies the detail and description of the test performed. Each payer (once the code is approved for Quest) makes their own coverage determinations based on that detail. There is also a module within DEX that provides a process for providing technical assessment information (clinical utility and validity) that can be accessed by the payer and used to help make coverage decisions.
Does the Z-Code process determine reimbursement amounts?
No, each payer makes their own reimbursement decisions. Z-Code assignment does not imply coverage or reimbursement.
Who has access to Quest assigned Z-Code Identifiers?
There are 4 Quest Lab Administrators that have direct access to all the information found in the DEX database. The Lab Administrator has the authority to add or edit lab tests, browse the catalog and Z-Code Identifiers, and manage the Quest account. A report can be pulled by the Lab Administrator and shared internally with all Quest sites.
Can I provide clients with Quest assigned Z-Code Identifiers?
Due to the usage terms of agreement with Palmetto GBA, Z-Codes cannot be published on the Quest website or provided to clients via email or phone without following specific Palmetto requirements. The requesting client/lab must register with DEX and agree to their terms of use and request sharing with Quest. Once access has been granted and confirmed, the client can look up any Quest assigned Z-Code in DEX or receive a report from the Quest Lab Administrator.
There is also a link on the Quest website which will describe this process and allow clients to download a report of all our Quest- assigned Z-Code Indicators for their own use. In order to gain access to our Z-Codes, you will need the NPI number that was used to register your lab in DEX. If you don’t have the correct NPI number or if you have not registered in DEX, the program will not allow access to our Z-Code report.
*It should be noted that our assigned Z-Codes can be updated at any time and if you are using an old, downloaded copy from the website, it may not be the most updated and current version.
What information can client laboratories see in DEX?
Only general test information including test name, test code, test description, FDA status, CPT Codes, and Z-Code Identifier is visible to the client. Specific methodology and proprietary information are not visible.
If a test is performed at multiple sites, do I need a Z-Code Identifier for each site?
Z-Code Identifiers are assigned based on the uniqueness of each test. If a test is performed by a different laboratory, but for the same analyte(s) and by the same methodology, they would use the same Z- Code Identifier. If the test is performed using a different methodology or includes different mutations or primers, then an individual Z-Code Identifier would be assigned to each.
What information is required on a Z-Code application?
The application requires general information including test name and description, test code, usage, FDA information, specimen information, and CPT codes. It also requires information regarding the molecular component, including specific genes/alleles/exons/mutations, as well as the specific methodology.
How long does it take to get my Z-Code Identifier assigned?
It can take up to 30 business days for a test to be assigned a Z-Code identifier and to appear in the DEX catalog.
When should I apply for a Z-Code Identifier?
The application for a Z-Code should be submitted as early as possible during the activities of a new test launch, preferably at least 30 days prior to launch date to prevent billing issues.
The new test must have an assigned test code and all details of the test identified before requesting a Z-Code for that test.
How and where is the Z-Code placed on the claim?
On the electronic 837p claim form, the Z-Code is placed in the professional claim line (SV101-7).
On the paper UB04 claim form, the Z-Code is placed in the comment field at the header level (Box 80).

The placement of the Z-Code is handled by the Medical Coding Group.