Validating Immunoassays: Best Practice Principles

Bioanalysis can be both qualitative and quantitative in the determination of drugs and metabolites in biological fluids, and used to support bioequivalence, pharmacokinetic and toxicokinetic studies. Traditionally this has been carried out using chromatographic techniques for the analysis of small molecules. However, with the ever-increasing number of macromolecular therapeutics coming onto the market, bioanalytical methods have diverged and many ligand binding assays such as immunoassays are being used. It is essential that high quality data are produced in these studies, since the results will be used in support of regulatory submissions. Several bioanalytical method validation conferences have been held to address the quality of data submitted to regulatory authorities. This article will review the progress and evolution of the guidelines on validation of immunoassays and briefly discuss the major issues related to their validation and how they differ from chromatographic assays.

HISTORY OF BIOANALYTICAL METHOD VALIDATION WORKSHOPS

The first workshop on bioanalytical method validation was a meeting between the American Association of Pharmaceutical Scientists (AAPS) and the US Food and Drug Administration (FDA) in 1990 (1). This workshop resulted in the draft Guidance on Bioanalytical Method Validation which was issued by the FDA in 1999. A section on microbiological and ligand-based assays was included with the recommendations, and described only selectivity and quantification issues. The second AAPS workshop was held in 2000 and was instrumental in finalising the FDA Bioanalytical Guidance which was issued in 2001 (2,3).