Abstract: This invention discloses a pretreatment approach for blood and bodily fluids to remove unwanted protein interferences in the measurement of analytes. Enzymes either contained in a cartridge or immobilized on a solid support break down proteins that complex with the analyte to shield it from detection. This pretreatment significantly enhances the detectability of analytes and does not require subsequent clean-up steps that would normally be required to ensure the functionality of the analysis method, thereby, creating a simple yet powerful approach for sample pretreatment in a variety of settings ranging from a complex laboratory infrastructure to a field deployable application.