Critical quality attribute (CQA)

A physical, chemical, biological or microbiological property that should be within an appropriate limit, range or distribution to ensure the desired product quality, as defined in ICH Q8. For an antibody, CQAs typically include aggregates, charge variants, glycosylation and potency; for an AAV vector, the full and empty capsid ratio. Whether an attribute is critical depends on how severe the harm to patients would be if it went out of range. Japanese documents use CQA and the Japanese term interchangeably. The choice of CQAs drives which process parameters are critical and which analytical methods are needed.