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

MSI (by PCR), dMMR (by IHC), 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 dMMR/MSI testing has not previously been performed on the tumor. NGS assays must be validated to demonstrate >=95% concordance with MSI by PCR; performing both an NGS panel and a separate MSI PCR on the same specimen will be denied. Specific CPT codes (dMMR: 88342/88341; MSI: 81301; NGS: 81479) and documentation of prior test status and NGS validation are required for claims.

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

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