Microsatellite instability (MSI) testing is used to screen for
Lynch syndrome. The current technique for MSI determination requires
DNA from normal and neoplastic tissue and is expensive and laborious. Five quasi-monomorphic markers (NR-21, BAT-25, MONO-27, NR-24, and BAT-26) are included in the
Promega MSI analysis kit. With the working hypothesis that this 5-marker panel can accurately determine the MSI status of
colorectal tumors without using paired control
DNA, we evaluated 478
colorectal tumors and divided them into a test group (N=172, colorectal
adenocarcinomas) and a validation group (N=306 including 179 colorectal
adenocarcinomas and 127
adenomas). The quasi-monomorphic variation range of each marker was generated from the test group (172 normal samples) and used as a reference value in the subsequent interpretation of MSI status in the test and validation groups. Considering the MSI result using a 5-marker panel with paired control
DNA as the gold standard, we identified 136 microsatellite stable (MSS) and 36
microsatellite instability-high (MSI-H)
colorectal tumors in the test group and 259 MSS and 47 MSI-H
colorectal tumors in the validation group. Using the quasi-monomorphic variation range of each marker rather than paired normal
DNA, the 5-marker panel identified all MSI-H
colorectal tumors in the test and validation groups, when MSI-H was defined as ≥2 unstable markers. Our study demonstrates that the 5-marker panel within a multiplex polymerase chain reaction of the
Promega MSI analysis kit accurately identifies all MSI-H and 95.2% MSS
colorectal tumors without using paired normal
DNA.