Is there a difference between the previous MSI/MSS reference standards and these revised products?

There is no change in the way the previous and the revised products are manufactured, however, there is a slight change in the QC process. Standards released since May 2023 (batches: 61956, 61957 and above for HD830, HD831 respectively) had the MSI status checked using ThermoFisher's TrueMark MSI Assay, whereas the previous product manufactured in 2022 and before (batches until 38873, 38874 for HD830, HD831 respectively) were tested using Promega MSI Analysis kit. The kit used can be confirmed by checking the batch-specific CoAs.