Clinical performance of the Idylla MSI Test for a rapid assessment of the DNA microsatellite status in human colorectal cancer

Abstract In this study we evaluated the clinical performance of the Idylla MSI Test (Investigational Use Only) in 330 colorectal carcinoma samples (all stages). This test is fully automated from formalin-fixed, paraffin-embedded slide to result, and gives a result in less than 2.5 hours. Compared to the Promega MSI Analysis System, Version 1.2, an overall agreement, sensitivity, and specificity of 99.7%, 98.7%, and 100% was reached, respectively. Whereas seven samples were invalid with the Promega MSI Analysis, only two were invalid with the Idylla MSI Test. Compared to the historical immunohistochemistry (IHC) data, an overall agreement, sensitivity, and specificity of 98.7%, 94.4%, and 100% was observed, respectively. Tumor mutation burden analysis of the discordant IHC cases was in favor of the Idylla MSI Test result in three of the four samples. Furthermore, for those cases where the IHC data were invalid or hard to interpret as sole loss of one DNA mismatch repair deficiency marker was observed, Idylla MSI Test results were always valid and accurate. Overall, we have demonstrated that the Idylla MSI Test is an accurate, fast screening assay for the detection of microsatellite status in colorectal cancer patients, with a low amount of invalid results.