The proximity extension assay (PEA) is a method for detecting and quantifying the amount of many specific proteins present in a biological sample such as serum or plasma.
In contrast, PEA is performed without a solid phase in a homogeneous one tube reaction solution where in sets of antibodies coupled to unique DNA sequence tags, so called proximity probes, work in pairs specific for each target protein.
Target binding by the proximity probes increases their local relative effective concentration of the DNA-tags enabling hybridization of weak complementarity to each other which then enables a DNA polymerase mediated extension forming a united DNA sequence specific for each target protein detected.
Subsequently, these amplicons are detected and quantified by either real-time PCR or next generation DNA sequencing by DNA-tag counting.
[5] Only cognate pairs of sequence are detected as true signal, enabling multiplexing beyond solid phase capture methods limited at around 30 proteins at a time.