Clinical Utility of a Fully Automated Microsatellite Instability Test with Minimal Hands-on Time.J Pathol Transl Med 2019JP
Microsatellite instability (MSI) analysis is becoming increasingly important in many types of tumor including colorectal cancer (CRC). The commonly used MSI tests are either time-consuming or labor-intensive. A fully automated MSI test, the IdyllaTM MSI assay, has recently been introduced. However, its diagnostic performance has not been extensively validated in clinical CRC samples.
Materials and Methods
We evaluated 133 samples whose MSI status had been rigorously validated by standard PCR, clinical next-generation sequencing (NGS) cancer panel test, or both. We evaluated the diagnostic performance of the IdyllaTM MSI assay in terms of sensitivity, specificity, positive, and negative predictive value, as well as various sample requirements, such as minimum tumor purity and the quality of paraffin blocks.
Compared with the gold standard results confirmed through both PCR MSI test and NGS, the Idylla™ MSI assay showed 99.05% accuracy (104/105), 100% sensitivity (11/11), 98.94% specificity (93/94), 91.67% positive predictive value (11/12), and 100% negative predictive value (93/93). In addition, the Idylla™ MSI assay did not require macro-dissection in most samples and reliably detected MSI-high in samples with approximately 10% tumor purity. The total turnaround time was about 150 minutes and the hands-on time was less than 2 minutes.
The Idylla™ MSI assay shows good diagnostic performance that is sufficient for its implementation in the clinic to determine the MSI status of at least the CRC samples. In addition, the fully automated procedure requires only a few slices of formalin-fixed paraffin-embedded (FFPE) tissue and might greatly save time and labor.