NPPB and heart failure: We demonstrated the abilityof this combined assay-reader system to measure NT-proBNP levels,a canonical heart failure marker, in complex media and patient samples.From the plurality of particles added per well, we were able to obtaintens of measurements per sample, thereby improving quantitation capabilitiesand reducing measurement error from using a low-cost imaging system.Particle numbers can also be adjusted depending on the applicationand sensitivity requirements.