Olink’s Proximity Extension Assay (PEA) technology. (A) Antibody pairs, labelled with DNA oligonucleotide tags, bind to the target protein in solution. (B) When the oligonucleotides are brought into proximity by the binding of the abtibody pairs, they hybridize and are extended by a DNA polymerase step. (C) This newly created piece of DNA “barcode” is unique for each antibody pair and is then amplified by PCR ready for readout by either Next Generation Sequencing (NGS) for Olink Explore products, or quantitative PCR (qPCR) for Olink Target products. Up to 384 different proteins can be measured simultaneously from approximately 1 µL of blood or other type of biological sample using this method.