Multiplex (assay)

A multiplex assay is a type of assay used in research to simultaneously measure multiple analytes (dozens or more) in a single run/cycle of the assay. It is distinguished from procedures that measure one analyte at a time.

Multiplex assays within a given application area or class of technology can be further stratified based on how many analytes can be measured per assay, where "multiplex" refers to those with the highest number of analyte measurements per assay (up to millions) and "low-plex" or "mid-plex" refers to procedures that process fewer (10s to 1000s), though there are no formal guidelines for calling a procedure multi-, mid-, or low-plex based on number of analytes measured. Single-analyte assays or low-to-mid-plex procedures typically predate the rise of their multiplex versions, which often require specialized technologies or miniaturization to achieve a higher degree of parallelization.

Multiplex assays are widely used in functional genomics experiments that endeavor to detect or to assay the state of all biomolecules of a given class (e.g., mRNAs, proteins) within a biological sample, to determine the effect of an experimental treatment or the effect of a DNA mutation over all of the biomolecules or pathways in the sample. The ability to perform such multiplex assay experiments measuring large numbers of biomolecular analytes has been facilitated by the completion of the human genome sequence and that of many other model organisms.

Multiplex assays are often used in high-throughput screening settings, where many specimens can be analyzed using a multiplex (or other) assay. Strictly speaking, a multiplex assay is not necessarily high-throughput. When the execution of a single multiplex assay generates data for a large number of analytes (e.g., gene expression levels for all genes in the human genome), it is considered high-throughput. However, the ability to rapidly process multiple samples in an automated fashion is what characterizes high-throughput techniques. Massive parallelization of assays is one way to achieve "high-throughput" status. Another way is via automation of manual laboratory procedures.

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