Methods and applications of percentile estimation

Percentile is ubiquitous in statistics and plays a significant role in the day-to-day statistical application. FDA Guidance for Industry: Assay Development for Immunogenicity Testing of Therapeutic Protein Products (2016) recommends the use of a lower confidence limit of the percentile of the negative subject population as the cut point to guarantee a pre-specified false-positive rate with high confidence. Shen proposed and compared an exact t approach with some approximated approaches. However, the exact t approach might be compromised by computational time and complexity. In this article, we proposed to use a UMOVER method as a potential alternative for percentile estimation for one application to screening and confirmatory cut point determination due to its easy implementation and similar performance to the exact t approach. The applications and performance comparison with different approaches are investigated and discussed. Furthermore, we extended the proposed method for the comparison of the percentile of the test product and percentile of the reference product followed by numerical studies.