Detection of microsatellite instability in a panel of solid tumours with the Idylla MSI Test using extracted DNA

Aim During the last few years, determination of microstatellite instability (MSI) status has become a routine part of clinical practice, essentially to detect Lynch syndrome. Recently, MSI testing has increased with the development of immunotherapy and has expanded to a large panel of solid tumours. The aim of our work was to evaluate a fully automated system developed by Biocartis, the Idylla MSI Test, which performs an MSI analysis within 150 min. Methods A comparison between pentaplex PCR, immunohistochemistry and Idylla MSI Test was performed in 53 colorectal carcinoma samples, 7 small intestine adenocarcinomas, 15 duodenal and pancreatic adenocarcinomas, 16 gastric tumours, 15 endometrial adenocarcinomas, 5 ovarian carcinomas and 4 cases of urinary tract tumours using extracted DNA. Limit-of-detection (LOD) experiment was also done using a commercial DNA known to harbour MSI phenotype. Results The overall sensitivity was 94% and the overall specificity was 100%. Two invalid and three false-negative results were observed. Our experiments showed that the amount of DNA loaded into the cartridge was decisive and should be superior to 25 ng. LOD comprised between 4% and 8%. Conclusion Overall, we have demonstrated that the Idylla MSI Test is a rapid and valid option to detect MSI phenotype which can be used in a large panel of solid tumours.

Automated summary

The aim of the study was to evaluate the Idylla MSI Test by Biocartis for MSI analysis, which can be completed within 150 minutes. The results showed high sensitivity (94%) and specificity (100%), with a few invalid and false-negative results observed. The experiment also emphasized the importance of DNA quantity loaded into the cartridge, with a LOD between 4% and 8%.