Quantification below the LLOQ in regulated LC–MS/MS assays: a review of bioanalytical considerations and cautions

What is it about?

This paper discusses the dangers of using LC-MS/MS bioanalytical data below the lower limit of quantification (BLQ) for pharmacokinetic (PK) purposes. Beyond regulatory restrictions, some important bioanalytical factors that can adversely impact BLQ data include signal to noise, baseline aberrations, matrix effect, coeluting interferences, carry over, chemical stability and adsorption issues. Special considerations apply to protein LC-MS/MS methods. These factors are explained using examples. A method is proposed to test BLQ values using extended range sample analysis employing standards and quality control samples prepared at BLQ concentrations. These data can be brought to the regulators to assess possible BLQ estimations and to plan any required validation experiments. BLQ estimations are discouraged for regulated studies, except where bioanalytical and PK scientists confer with their regulatory agencies.

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