Beyond accuracy, precision and TAE: Direct assay validation against product specification aligned with USP <1033>

Current validation methodologies – whether based on accuracy and precision or total analytical error (TAE) and risk – fall short when the analytical target profile (ATP) is defined in terms of product and process specifications, as is the case in the USP <1033> guideline for biological assay validation. In this paper, we critically examine the limitations of these existing methodologies and introduce a statistically correct methodology tailored to the ATP formulation. While this novel methodology is demonstrated in the context of potency assay validation in line with the USP <1033> guideline, it is broadly applicable to other analytical procedures governed by ICH Q2(R2), with only minor adaptations. A freely accessible online application has also been developed to facilitate discussion and adoption of the novel methodology in practice.