Billing and Coding: MolDX: Microsatellite Instability-High (MSI-H) and Mismatch Repair Deficient (dMMR) Biomarker for Patients with Unresectable or Metastatic Solid Tumors

MSI and dMMR biomarker testing is covered for patients with unresectable or metastatic solid tumors if MSI/dMMR testing has not already been performed on the tumor. Covered methods include dMMR by IHC, MSI by PCR, or a multi-gene NGS panel that includes MSI loci and MLH1, MSH2, MSH6, and PMS2; NGS assays must be validated with ≥95% concordance to MSI by PCR. Redundant testing (NGS panel plus separate MSI PCR) and unvalidated NGS assays will be denied; submit specified CPT codes (88342/88341 for IHC, 81301 for MSI PCR, 81479 for NGS) and validation/prior-test documentation as required.

"MSI or dMMR testing is reasonable and necessary for patients with unresectable or metastatic solid tumors when MSI/dMMR testing has not previously been performed on the patient's tumor sample."

Sign up to see full coverage criteria, indications, and limitations.