Microsatellite Instability Assay (MSI)

Microsatellite instability (MSI) results from an accumulation of insertion or deletion of repeating units during DNA replication in tumor cells with a deficient mismatch repair (MMR) system. MSI status is associated with response/resistance to certain immune checkpoint inhibitors.

IQVIA MSI assay utilizes multiplex, fluorescent PCR and capillary electrophoresis to enable sensitive detection of five mononucleotide repeat markers (BAT-25, BAT-26, NR-21, NR-24 and MONO-27) in tumor FFPE specimens. Microsatellite instability at two or more mononucleotide loci is interpreted as MSI-High; microsatellite instability at a single mononucleotide locus is interpreted as MSI-Low; no instability at any of the loci tested is interpreted as microsatellite stable (MSS).

MSI Assay Specifications
Markers	BAT-25, BAT-26, MONO-27, NR-21, and NR-24 microsatellite loci
Specimen Requirements	Tumor: 3 x 5um FFPE tumor slides or 3 curls or FFPE block or DNA. Minimum 20% neoplastic cellularity required. Normal: either whole blood (1-3 mL, K2EDTA) or tumor FFPE slides with clearly indicated normal tissue area or 3 x 5um normal tissue FFPE slides, curls or block. If H&E stained slide with indicated tumor normal areas is not available, will perform H&E assessment and determine specimen adequacy.
Assay Method	OncoMate^® MSI Dx Analysis System
System Compatibility	Thermo Fisher Scientific SeqStudio Flex
Regulatory Tier	RUO, GCP, CAP-CLIA
Deliverables	MSI Status report. Exact number of MSI markers available as custom report.