Gene Expression Detection Assay for Cancer Clinical Use

Narrandes, Shavira; Xu, Wayne

Sensitivity refers to the minimum amount of substance, such as RNA, detected per sample in an experimental assay. qRT-PCR and PCR have a reported sensitivity of 10 copies mRNA per cell, with as many as 200 copies per cell having been detected for PCR. 92 , 93 As little as 3 copies per cell have been detected in PCR, implying that this number could be similar for qRT-PCR. 94 Similarly, DNA microarrays can detect from 1-10 copies of mRNA per cell. 83 Both nCounter and MiSeq have the ability to sense <1 copy of mRNA per cell; nCounter utilizes region-specific colour-coded probes to bind to a single transcript, whereas MiSeq can generate a cluster of 1000 copies from a single transcript. 46, 95 Lastly, sensitivity for TMAs can be analyzed in a number of ways as it may depend on the size of the tissue spot in the array or the sensitivity of the tests (e.g. FISH, ISH) being used. For example, TMAs can array up to 1000 different sample spots on a single array, allowing 0.6 mm as the smallest sample size that can be taken with efficient detection results; in situ hybridization is shown to have a sensitivity of 10-20 mRNA copies per cell. 67, 68, 96