Attenuating dye for interrogating fluorescence from multiple surfaces, corresponding method

A method for attenuating non-specific fluorescence in a microfluidic device (9), the microfluidic device (9) including a microfluidic assay- chamber (10) for analyzing a plurality of target analytes in a body fluid using the signal generated by fluorescent detector molecules (52;52') each specific for a target analyte (55;55'), an attenuating dye (60) for attenuating the signal emitted by fluorescent detector molecules (52;52') specifically bound to the surfaces (14d) of the chamber (10) other than an optically clear surface (14f), and method for determining the signal generated by each of the plurality of analytes (55;55').