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 testing (by IHC, PCR, or a multi-gene NGS panel that includes MSI loci and MLH1/MSH2/MSH6/PMS2) is covered for patients with unresectable or metastatic solid tumors when testing has not previously been performed on the tumor sample. NGS assays must be validated to demonstrate ≥95% concordance with MSI by PCR; simultaneous billing of a multi-gene NGS panel and a separate MSI PCR for the same sample will be denied. Claims must use the specified CPT codes and units for each testing method (IHC: 88342/88341, PCR: 81301, NGS: 81479).

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

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