Does it matter whether one uses MSI PCR testing versus IHC for MMR deficiency testing inorder to determine eligibility for immunotherapy?  

In colorectal cancers, PCR is likely more sensitive (+2-5%) for detecting MSI but more costly with a longer turn around time.  PCR may miss PMS2 and MSH6 alterations that are difficult to detect are not always MSI-high (but they are germ-line alterations). IHC is easy to incorporate i...

Immunohistochemistry (IHC) assays detect dMMR, or deficiency in the mismatch repair proteins. Polymerase chain reaction, or PCR, detects microsatellite instability-high (MSI-high) status at the genomic level. Functionally, they mean the same thing - tumors that test positive for either assay should ...