A method of conducting an assay on a sample, the method comprising: (i) introducing a sample, into a microfluidic cartridge such that any analyte present in the sample is capable of being bound by the analyte binding agent present in the cartridge; the cartridge comprising: a sample port for introducing said sample into the cartridge, a substrate comprising one or more microfluidic channels disposed therein and comprising a binding agent disposed within said channel(s) for binding any of said analyte within the sample the binding agent being attached or otherwise bound to a paramagnetic or magnetic particle; and a label, adapted to specifically bind any captured analyte for use in detecting an amount of the analyte present in the sample; and a detection area, within or wholly comprising an area where analyte and label binding occurs, said detection area, from which bound analyte is removed, allowing determination of said analyte concentration indirectly by measurement of any remaining unbound label and (ii) detecting, a level of label present in the detection area (both complexed and uncomplexed to analyte), in order to obtain a first reference/control value; (iii) removing complexed analyte/label from the detection area using a magnet or electromagnetic force; and (iv) detecting in the detection area any uncomplexed and/or unreacted label that remains after removal of said complexed analyte/label, wherein a decrease in signal from the first reference/control value is directly proportional to the amount of analyte present in the sample. (i) introducing a sample, into a microfluidic cartridge such that any analyte present in the sample is capable of being bound by the analyte binding agent present in the cartridge; the cartridge comprising: a sample port for introducing said sample into the cartridge, a substrate comprising one or more microfluidic channels disposed therein and comprising a binding agent disposed within said channel(s) for binding any of said analyte within the sample the binding agent being attached or otherwise bound to a paramagnetic or magnetic particle; and a label, adapted to specifically bind any captured analyte for use in detecting an amount of the analyte present in the sample; and a detection area, within or wholly comprising an area where analyte and label binding occurs, said detection area, from which bound analyte is removed, allowing determination of said analyte concentration indirectly by measurement of any remaining unbound label and a sample port for introducing said sample into the cartridge, a substrate comprising one or more microfluidic channels disposed therein and comprising a binding agent disposed within said channel(s) for binding any of said analyte within the sample the binding agent being attached or otherwise bound to a paramagnetic or magnetic particle; and a label, adapted to specifically bind any captured analyte for use in detecting an amount of the analyte present in the sample; and a detection area, within or wholly comprising an area where analyte and label binding occurs, said detection area, from which bound analyte is removed, allowing determination of said analyte concentration indirectly by measurement of any remaining unbound label and (ii) detecting, a level of label present in the detection area (both complexed and uncomplexed to analyte), in order to obtain a first reference/control value; (iii) removing complexed analyte/label from the detection area using a magnet or electromagnetic force; and (iv) detecting in the detection area any uncomplexed and/or unreacted label that remains after removal of said complexed analyte/label, wherein a decrease in signal from the first reference/control value is directly proportional to the amount of analyte present in the sample.