Introduction: NanoString nCounter technology, a novel molecular assay, is gaining prevalent use in clinical settings as it can overcome some common constraints that are associated with the use of polymerase chain reaction (PCR). Compared to PCR, NanoString technology does not involve any amplification steps, which significantly minimizes the chance of contamination. NanoString measures the number of mRNA transcripts directly by 'molecular counting', as up to 800 colored probes can be run simultaneously in a single reaction. Areas covered: This manuscript reviews the principle of NanoString and covers the main applications of NanoString in companion diagnostics with a focus on cancer immunotherapy and disease prognosis estimation. This review has also taken a step in the direction of personalized medicine, with the application of NanoString on the realm of companion diagnostics. Expert opinion: NanoString is going to take a vital role in companion diagnostics and personalized medicine, owing to its simple and easy to use characteristics. Yet, the use of NanoString requires normalization of expression level, which is represented by the copy number of respective mRNA, with a reference gene. Furthermore, difficulty in probe design, which demands prior knowledge of known sequence, has also been a limitation of NanoString.
Keywords: NanoString; companion diagnostics; gene expression; molecular barcode; personalized medicine.