Detailed and extensive data analysis of 1) CUB assay performance captured in SME assessment, PR947177, and 2) correlation of DP and used DS release CUB and DS Glycan Peak Group 1 (PG1) captured in SME assessment, PR 947175 indicate that 1) CUB assay is potentially one of the contributing factors; and 2) no direct evidence of DP above mean trend due to DS quality shift was observed probably because the CUB assay variability outweighs the trend based on the facts that Glycan PG1 is a direct indication of enzyme update and the observed significant statistical relationship between combined site DS PG1 and DP CUB. Further SME assessment of DS quality review including the upstream used to produce the DS/DP with the above mean CUB value did not disclose any known process change which may contribute to the observed trend. Since this current CUB assay is being performed using self-control, an independent assay control as a CAPA action (PR965715) is being evaluated to improve assay performance and/or capacity.