Quantification of low abundance proteins in body fluids represents a promising new field to explore. To this end, Biosims has combined protein microarrays with mass spectrometry. It enables a digital quantification with an unsurpassed sensitivity allowing it to quantify protein panels down to the fg/ml range. Biosims microarrays feature multiplex spots of sandwich immunoassays, where detection antibodies are quantified using one discrete mass-tag, thus needing no fluorescence