page_title: Cepheid Inc
section_title: System
hierarchical_section_title: Cepheid Inc / System
caption_attribution_description: Scheme of the principle of the FISH (Fluorescent in situ hybridization) Experiment to localize a gene in the nucleus.
context_page_description: Cepheid is an American molecular diagnostics company. Its systems automate traditional nucleic acid tests. The tests can be used to identify and analyze pathogens and genetic disorders. Cepheid sells clinical tests for healthcare-associated infections, infectious diseases, sexual health, oncology and genetics.
  The cartridges used in Cepheid's testing machines are single-use and must be bought from the manufacturer. The company has been accused of profiteering, with a Doctors without Borders analysis claiming that Cephid is charging over six times the cost of production for COVID-19 test cartridges sold to developing countries.
context_section_description: Cepehid owns the GeneXpert rapid molecular diagnostic system, its main product. The system was developed in the 1990s; the design remained substantially the same from the turn of the century to 2020. Similar tests have subsequently been developed by Abbott and Roche.
  The GeneXpert system identifies organisms from their DNA. It extracts genetic material from a sample and, in the case of RNA viruses, it converts the RNA into DNA first. The GeneXpert test is basically an automated version of standard real-time PCR (polymerase chain reaction) amplification and detection.
  Each sample to be tested is added to a single-use GeneXpert cartridge, sold by Cepheid; after this, the tests are self-contained and fully-automated. The cartridge contains a series of injection-moulded plastic chambers, which hold the chemicals and the sample. To run the test, multiple cartridges are loaded into a desktop machine (also made by Cepheid, but reusable). The sample and  chemicals are moved into the test chambers using microfluidics: there is a rotary valve in the center, and some small plungers; the plungers push the sample into the valve, the valve rotates to a new position, and the sample is them pulled out into a new chamber. The machine provides the temperature cycling needed for the PCR (much like a programmable oven). This makes many copies of DNA matching the sample (amplification). Finally, the presences or absence of the pathogen is detected using FISH probes. These are short sections of DNA which have been made to attach to a fluorescent molecule. If the DNA from the sample matches the DNA of the FISH probes, the two bind, and the sample fluoresces. An optical system detects the glow, or its absence. A test for a new disease can be made by simply swapping in a FISH probe that matches the sequence of the new disease.
caption: FISH testing, a standard techniqure for identifying pathogens, is done automatically by Cepehid's GeneXpert test systems
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