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Immunohistochemistry (IHC)
Test Description

Programmed cell death ligand 1 (PD-L1) is a transmembrane protein involved in cellular and humoral immune response regulation. PD-L1 expression has been found in a variety of cancers expressed on tumor and/or immune cells.  This lab developed test uses the Zeta PD-L1 monoclonal antibody clone ZR3 to detect PD-L1 in formalin-fixed paraffin-embedded tissues. The utility of PD-L1 (ZR3) in predicting the response to anti-PD-1/PD-L1 has not been determined and no standardized scoring criteria currently exist. For therapies and indications that have an FDA-approved PD-L1 companion diagnostic, it is recommended to use the associated FDA approved PD-L1 test.           

All PD-L1 IHC test options may be viewed here.
Scoring for this test is calculated by taking the total PD-L1 score is the sum of the number of staining tumor cells and inflammatory cells divided by the number of total viable tumor cells. Results are reported as “detected” if the total score is ≥1 and “not detected” if <1. This algorithm is comparable to Combined Positive Score used with PD-L1 22C3.    

Specimen Requirements
  • A formalin-fixed, paraffin-embedded (FFPE) tissue block is preferred specimen type
  • One (1) unbaked, unstained slide for H&E staining (required) and two to three (2-3) positively charged unstained slides (all cut at 4-5 microns) for each test/antibody ordered
  • Block and slide identifiers should be clearly written and match exactly with the specimen ID and specimen labeling as noted on the requisition.
Storage and Transportation

Use cold pack for transport. Make sure cold pack is not in direct contact with specimen.

CPT Code(s)*
New York Approved
Level of Service
Turnaround Time

Global: 48 hours, Tech-Only (stain only): 24 hours

*The CPT codes provided with our test descriptions are based on AMA guidelines and are for informational purposes only. Correct CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed.