Statistical Equivalence Testing for Assessing Bench-Scale Cleanability - The two-one-sided t-test compares the equivalency of two data sets. - BioPharm International


Statistical Equivalence Testing for Assessing Bench-Scale Cleanability
The two-one-sided t-test compares the equivalency of two data sets.

BioPharm International
Volume 23, Issue 2


To ensure consistency and adherence, a procedure should be established and analysts should be trained to perform such experiments. Because this method provides relative product cleanability, it is important that each experiment be conducted in a consistent manner. When performing cleaning evaluations to compare new products to the validated worst case, an additional check can be incorporated to ensure that each evaluation is conducted in a consistent manner. This is achieved by comparing the data for a control molecule (e.g., a worst-case product) to the established data set or the "gold standard" generated for the control during the characterization study. The same statistical method, the TOST, can be used to fulfill this requirement. For example, an analyst may need to perform an experiment to determine the cleanability of new product N relative to the validated product W. The cleanability of validated product W has been pre-established by prior characterization work. To ensure that the analyst performed the experiment adequately, a comparability test using the TOST can be used to compare the equivalency between data generated by an analyst for product W to the established data set. The equivalency between the two data sets would demonstrate that the experiment was indeed adequate and reliable.


The two-one-sided t-test (TOST) is a statistical method well accepted by the FDA and industry for evaluating the comparability between two groups of data. In the case of a scale-down cleaning evaluation, this statistical approach has been applied to determine the relative cleanability of two products. The TOST compares two group means and their confidence intervals by comparing them to a predefined equivalence limit. The predefined equivalence limit should be established by evaluating the variability involved with such experimental evaluations. To incorporate an additional check for analyst consistency, TOST can be applied to ensure that the data obtained from different analysts for a particular product (control molecule) are equivalent.


The authors thank Ed Walls and Erwin Freund (Process Development, Amgen, Inc.) for reviewing this work and providing their valuable suggestions.

Cylia Chen is a senior associate scientist, Nitin Rathore is a senior scientist, and Wenchang Ji is a principal scientist, all in drug product and device development, and Abe Germansderfer is a principal quality engineer, corporate quality, all at Amgen, Inc., Thousand Oaks, CA, 805.313.6393,


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