Developing and deploying tests for SARS-CoV-2 is crucial – The Economist
Posted: March 19, 2020 at 5:42 pm
Mar 19th 2020
WE HAVE A simple message to all countries. So said Tedros Adhanom Ghebreyesus, the head of the World Health Organisation (WHO) at a news conference held in Geneva on March 16th. Test, test, test. All countries should be able to test all suspected cases, they cannot fight this pandemic blindfolded. Without adequate testing for SARS-CoV-2, the novel coronavirus that is now sweeping rapidly around the world, he said, there can be no isolation of cases and the chain of infection will not be broken. As if to prove the point, a vigorous policy of testing seems to have slowed the viruss spread in South Korea quite dramatically. And in Vo, a town in Italy, thorough and repeated testing of all 3,300 inhabitants has stopped new infections entirely.
Two main types of test are used to identify viral infections: genetic and serological. The first genetic test for SARS-CoV-2 was created just a few days after the viruss genomic sequence was published, on January 12th, by a group of Chinese researchers. Others, developed subsequently by public health bodies around the world (and also a few companies) have their own tweaks, but their broad principle is the same.
Each starts with a swab taken from the back of the nose or the throat of an individual suspected of being infected, in a search for RNAfor SARS-CoV-2 stores its genes as RNA, rather than the similar molecule, DNA, which animals such as human beings employ for the purpose. Because of this quirk, the first step of genetic testing is to copy any RNA collected into DNA, using an enzyme called reverse transcriptase. That done, the DNA is then amplified in quantity by a process called the polymerase chain reaction (PCR). The now-amplified DNA is sequenced and matched (or not) against the sequence that would be expected if the starting point was RNA from the virus.
Executed properly, genetic tests of this sort are extremely accurate. But they have limitations. One is that if the virus is present only at low levelsat the start or end of an infection, for exampletheir sensitivity drops. Also, taking a throat swab is neither simple nor foolproof. If the sampling probe goes insufficiently deeply into the orifice concerned, or fails to gather enough cells, the test might not work. Virologists say that the best sort of throat swabbing almost inevitably makes a patient gag or cough. This means that whoever is doing the swabbing needs to be protected from infection.
All this assumes that the tests themselves are designed properly. The WHO published protocols for a SARS-CoV-2 test in January, and most places which have created their own tests have based them on these instructions. In America, however, the Centres for Disease Control and Protection (CDC) designed its own protocols. Tests created using these American CDC protocols, which were distributed across the country to state-level public-health laboratories, turned out to be flawed. This no doubt contributed to Americas slower response to the unfolding crisis.
The actual apparatus used to carry out PCR tests of this sortregardless of the exact bug being tested foris commonplace in hospitals in rich countries, for it is used routinely to identify viruses from influenza to hepatitis to HIV. But the process is thereby centralised, and can be slow. It may take as long as 48 hours after a sample is collected for the result to be returned to a patient. What is needed is a test which can be conducted immediately after sampling, a process known as near-patient testing. This involves packing everything required for a testboth the instruments and the chemicalsinto a reasonably portable machine, designed specifically to look for SARS-CoV-2, that can be deployed away from a big hospital laboratory.
Several firms are working on such things. BioMrieux, a French biotechnology company, says it will have a test on offer by the end of March, and that it has an emergency-use authorisation for it from the Food and Drug Administration, which approves such devices for America. Cepheid, a Californian firm, will try to use a similar approval process to get its own coronavirus-specific test to market. This is a box, the size of a small laser printer, that ingests a sample, carries out an analysis and returns a result within a couple of hours.
Machines like these could be particularly valuable in places where public-health laboratories are few and far between. John Nkengasong, head of Africa CDC (an arm of the African Union unrelated to the American organisation of the same name), wrote in the Lancet in February of his concern about the spread of coronavirus across his continent, given the strong links between many African countries and China, the place where the pandemic began. One of his worries was the continents lack of testing capacity. At the start of 2020, only the Pasteur Institute in Senegal and the National Institute for Communicable Diseases in South Africa were able to carry out full-scale genetic detection of SARS-CoV-2.
Subsequent training, led by the WHO, has now enabled scientists in around 40 African countries to diagnose infection with the virusbut this can still be done only in each countrys central public-health laboratory. Near-patient testing would help a lot. And many health-care workers in Africa are already familiar with similar self-contained diagnostic machines, because they have been used extensively to track the efficacy of antiretroviral therapy for HIV.
Genetic tests identify active infections. But to understand properly how SARS-CoV-2 is spreading through a population it is also important to know who has been infected in the past and recovered. That is where serological tests come in. They look not for RNA in swab samples, but for antibodies in blood samples. Antibodies usually hang around in a persons bloodstream well after an infection has cleared. They thus form a historical record of the pathogens people have been exposed to over the course of their lives.
Each antibody is tailored to latch onto a specific protein on the surface of a pathogen, thus disabling it. A serological test for SARS-CoV-2 therefore works by using such a proteinreferred to as an antigento capture antibodies from a blood sample. Most tests under development focus on spike, a protein which protrudes prominently, and in many places, from the surface of the otherwise-spherical SARS-CoV-2 virus particle. In a typical test, a blood sample would be placed into a test tube coated inside with the antigen. If relevant antibodies are present, they will stick to the antigen. Depending on the design of the test, a positive result could produce a colour change or emit light to indicate success. The whole thing is reasonably cheap and could give results in minutes.
BioMedomics, a firm in North Carolina, for example, has designed a serological test for SARS-CoV-2 that needs only a few drops of blood from a finger prick, and which gives results in 15 minutes. It includes a hand-held plastic stick which looks similar to that from a pregnancy-testing kit. And, similarly to those tests, it uses coloured lines to indicate the presence of particular antibodies. The company says the test has already been widely used by Chinas public-health authorities, but has not yet been reviewed for use by Americas FDA.
Designing a serological test, then, is straightforward. Checking that it gives accurate results takes time, though. A common problem with such tests is that antibodies may cross-react, meaning that a test for SARS-CoV-2 might also show a positive result when it comes across a different coronavirusthe original SARS, perhaps, or one of the coronaviruses that cause colds. Testing the accuracy of these tests requires trials involving hundreds of people who are known to have had SARS-CoV-2 infections, and hundreds of others who are known not to have been infected.
Once validated, serological tests are fast and cheap to run at scale. They have already been deployed in China, Singapore and South Korea. Data on their efficacy, however, have not yet been publicly released or independently verified. Americas CDC is evaluating two serological tests and Public Health England, the relevant government body in that country, is also working on a test. Chris Whitty, Englands chief medical officer, said that the introduction of such a test would be a game changer in the quest to track and control the spread of SARS-CoV-2 across the population. It cannot come fast enough.
This article appeared in the Science and technology section of the print edition under the headline "Test acts"
Link:
Developing and deploying tests for SARS-CoV-2 is crucial - The Economist
- A New Price Tag for Breast Cancer Genetic Testing - Video [Last Updated On: May 4th, 2015] [Originally Added On: May 4th, 2015]
- Genetic testing technologies - Video [Last Updated On: May 4th, 2015] [Originally Added On: May 4th, 2015]
- Prostate Cancer Genetic testing - Video [Last Updated On: May 4th, 2015] [Originally Added On: May 4th, 2015]
- Genetic Testing - Video [Last Updated On: May 4th, 2015] [Originally Added On: May 4th, 2015]
- Genetic Testing - One of the Best Things to Happen to Me - littlemamauk - Video [Last Updated On: May 4th, 2015] [Originally Added On: May 4th, 2015]
- BowelGene - genetic testing - Video [Last Updated On: May 4th, 2015] [Originally Added On: May 4th, 2015]
- Genetic Testing Fact Sheet - National Cancer Institute [Last Updated On: May 22nd, 2015] [Originally Added On: May 22nd, 2015]
- Genetic Testing - Genetics Home Reference [Last Updated On: May 22nd, 2015] [Originally Added On: May 22nd, 2015]
- FAQ About Genetic Testing - Genome.gov [Last Updated On: May 31st, 2015] [Originally Added On: May 31st, 2015]
- Regulation of Genetic Tests [Last Updated On: June 9th, 2015] [Originally Added On: June 9th, 2015]
- Types of Genetic Testing - Genetics Home Reference [Last Updated On: June 29th, 2015] [Originally Added On: June 29th, 2015]
- Genetic Testing: What You Should Know - FamilyDoctor.org [Last Updated On: July 3rd, 2015] [Originally Added On: July 3rd, 2015]
- Genetic Testing - BRCA1 & BRCA2 Mutations | Susan G. Komen [Last Updated On: July 6th, 2015] [Originally Added On: July 6th, 2015]
- What is genetic testing? - Genetics Home Reference [Last Updated On: July 6th, 2015] [Originally Added On: July 6th, 2015]
- Genomics |Genetic Testing [Last Updated On: August 24th, 2015] [Originally Added On: August 24th, 2015]
- What is genetic testing? - American Cancer Society [Last Updated On: August 24th, 2015] [Originally Added On: August 24th, 2015]
- Genetic testing - WebMD [Last Updated On: September 2nd, 2015] [Originally Added On: September 2nd, 2015]
- Genetic Testing and Screening | Florida Hospital [Last Updated On: September 2nd, 2015] [Originally Added On: September 2nd, 2015]
- Genetic Testing Toledo OH - DNA Diagnostics Center [Last Updated On: September 29th, 2015] [Originally Added On: September 29th, 2015]
- Genetics - Genetic testing and counselling - NHS Choices [Last Updated On: October 25th, 2015] [Originally Added On: October 25th, 2015]
- Genetic Testing Germantown MD - DNA Diagnostics Center [Last Updated On: February 18th, 2016] [Originally Added On: February 18th, 2016]
- GeneDx | Genetic Testing Company | The DNA Diagnostic Experts [Last Updated On: February 18th, 2016] [Originally Added On: February 18th, 2016]
- Genetic Testing - kidshealth.org [Last Updated On: February 24th, 2016] [Originally Added On: February 24th, 2016]
- BRCA1 and BRCA2: Cancer Risk and Genetic Testing [Last Updated On: February 29th, 2016] [Originally Added On: February 29th, 2016]
- Genetic Testing - Breastcancer.org - Breast Cancer ... [Last Updated On: April 4th, 2016] [Originally Added On: April 4th, 2016]
- Frequently Asked Questions About Genetic Testing - Genome.gov [Last Updated On: April 10th, 2016] [Originally Added On: April 10th, 2016]
- Pregnancy & Prenatal Testing: Genetic Testing for Inherited ... [Last Updated On: April 19th, 2016] [Originally Added On: April 19th, 2016]
- Genetic Testing | Family Caregiver Alliance [Last Updated On: April 19th, 2016] [Originally Added On: April 19th, 2016]
- Genetic Testing - American Medical Association [Last Updated On: April 19th, 2016] [Originally Added On: April 19th, 2016]
- Genetic Testing - Cancer Treatment | CTCA [Last Updated On: April 19th, 2016] [Originally Added On: April 19th, 2016]
- genome.gov - FAQ About Genetic Testing [Last Updated On: April 27th, 2016] [Originally Added On: April 27th, 2016]
- Family Cancer Genetics Program at UC San Diego Moores ... [Last Updated On: May 2nd, 2016] [Originally Added On: May 2nd, 2016]
- Genetic Testing - Benefits, costs, and risks of genetic testing [Last Updated On: May 13th, 2016] [Originally Added On: May 13th, 2016]
- Myriad Genetics | Healthcare Professionals | About Genetic ... [Last Updated On: May 13th, 2016] [Originally Added On: May 13th, 2016]
- Genetic Testing | Gluten-Free Society [Last Updated On: May 13th, 2016] [Originally Added On: May 13th, 2016]
- Genetic testing - Canadian Cancer Society [Last Updated On: May 13th, 2016] [Originally Added On: May 13th, 2016]
- Genetic Testing and Molecular Biomarkers [Last Updated On: May 13th, 2016] [Originally Added On: May 13th, 2016]
- genetic testing | Britannica.com [Last Updated On: May 13th, 2016] [Originally Added On: May 13th, 2016]
- Genetic Testing: Best Defense Against Breast Cancer? [Last Updated On: May 13th, 2016] [Originally Added On: May 13th, 2016]
- Genetic Testing | Issue List [Last Updated On: May 13th, 2016] [Originally Added On: May 13th, 2016]
- Jewish Genetics, Part 1: Jewish Populations (Ashkenazim ... [Last Updated On: June 19th, 2016] [Originally Added On: June 19th, 2016]
- What Is Genetic Testing -- Information About Genetic Testing [Last Updated On: June 23rd, 2016] [Originally Added On: June 23rd, 2016]
- Genetic Testing Report - genome.gov [Last Updated On: June 23rd, 2016] [Originally Added On: June 23rd, 2016]
- Good Laboratory Practices for Molecular Genetic Testing ... [Last Updated On: June 26th, 2016] [Originally Added On: June 26th, 2016]
- Genetics and Cancer | American Cancer Society [Last Updated On: July 18th, 2016] [Originally Added On: July 18th, 2016]
- Genetic testing - FSH Society [Last Updated On: September 22nd, 2016] [Originally Added On: September 22nd, 2016]
- Myriad Genetics | Patients & Families | Genetic Testing 101 [Last Updated On: September 22nd, 2016] [Originally Added On: September 22nd, 2016]
- BRCA1 and BRCA2: Cancer Risk and Genetic Testing Fact Sheet ... [Last Updated On: September 22nd, 2016] [Originally Added On: September 22nd, 2016]
- FAQ About Genetic Testing - National Human Genome Research ... [Last Updated On: September 22nd, 2016] [Originally Added On: September 22nd, 2016]
- Genetic testing - Wikipedia [Last Updated On: November 1st, 2016] [Originally Added On: November 1st, 2016]
- Genetic Testing for Cancer Risk | Cancer.Net [Last Updated On: November 25th, 2016] [Originally Added On: November 25th, 2016]
- Cancer Genetics Risk Assessment and Counseling (PDQ ... [Last Updated On: December 20th, 2016] [Originally Added On: December 20th, 2016]
- Patients Who Tested Positive For Genetic Mutations Fear Bias ... - NPR - NPR [Last Updated On: July 1st, 2017] [Originally Added On: July 1st, 2017]
- Genetic Testing for the Healthy - Harvard Medical School (registration) [Last Updated On: July 1st, 2017] [Originally Added On: July 1st, 2017]
- Genetic testing Overview - Mayo Clinic [Last Updated On: July 1st, 2017] [Originally Added On: July 1st, 2017]
- The real reason why all women should get their DNA tested - Quartz [Last Updated On: July 4th, 2017] [Originally Added On: July 4th, 2017]
- DNA insurance: Why genetic testing could revolutionise the industry - Verdict [Last Updated On: July 4th, 2017] [Originally Added On: July 4th, 2017]
- Everything you need to know about the Government plan for genetic testing to treat cancer patients - BreakingNews.ie [Last Updated On: July 4th, 2017] [Originally Added On: July 4th, 2017]
- Greater access to genetic testing needed for cancer diagnosis and treatment - Cancer Research UK [Last Updated On: July 5th, 2017] [Originally Added On: July 5th, 2017]
- Chief medical officer calls for gene testing revolution - BBC News - BBC News [Last Updated On: July 5th, 2017] [Originally Added On: July 5th, 2017]
- Genetic Testing Facilities and Cost - Breastcancer.org [Last Updated On: July 5th, 2017] [Originally Added On: July 5th, 2017]
- Greater access to genetic testing needed for cancer diagnosis and ... - Medical Xpress [Last Updated On: July 7th, 2017] [Originally Added On: July 7th, 2017]
- Global Breast Cancer Predictive Genetic Testing Market Outlook 2022 - PR Newswire (press release) [Last Updated On: July 7th, 2017] [Originally Added On: July 7th, 2017]
- Invitae: Growth in Genetic Testing - Moneyshow.com (registration) [Last Updated On: July 7th, 2017] [Originally Added On: July 7th, 2017]
- Cystic Fibrosis Among Asians: Why Ethnicity-Based Genetic Testing is Obsolete - PLoS Blogs (blog) [Last Updated On: July 7th, 2017] [Originally Added On: July 7th, 2017]
- Hospital gets cardiac genetic test service created in memory of broadcaster's son - Belfast Telegraph [Last Updated On: July 8th, 2017] [Originally Added On: July 8th, 2017]
- David Frost cardiac genetic testing service opens - BBC News - BBC News [Last Updated On: July 8th, 2017] [Originally Added On: July 8th, 2017]
- UK's chief medical officer calls for gene testing revolution in cancer treatment - Daily Nation [Last Updated On: July 8th, 2017] [Originally Added On: July 8th, 2017]
- Konica Minolta buys US genetic test maker in $1B deal - BioPharma Dive [Last Updated On: July 10th, 2017] [Originally Added On: July 10th, 2017]
- Checking the cost of a genetic test - Chicago Tribune - Chicago Tribune [Last Updated On: July 11th, 2017] [Originally Added On: July 11th, 2017]
- Genomic Testing in Oncology: From Single Genes to Whole Genomes - Labiotech.eu (blog) [Last Updated On: July 12th, 2017] [Originally Added On: July 12th, 2017]
- Direct-To-Consumer Genetic Testing Can Be a Trip Down the Rabbit Hole - Newswise (press release) [Last Updated On: July 12th, 2017] [Originally Added On: July 12th, 2017]
- DNA Diagnostics Center brings four genetic testing options to retail - Drug Store News [Last Updated On: July 12th, 2017] [Originally Added On: July 12th, 2017]
- Jeans for Genes Day stall at Taree City Centre - Gloucester Advocate [Last Updated On: July 31st, 2017] [Originally Added On: July 31st, 2017]
- She thought she was Irish until a DNA test opened a 100-year-old mystery - Chicago Tribune [Last Updated On: July 31st, 2017] [Originally Added On: July 31st, 2017]
- Genetic testing: The new way to identify and train elite athletes? - USA TODAY High School Sports [Last Updated On: July 31st, 2017] [Originally Added On: July 31st, 2017]
- Mail order genetic tests for health risks. How much do you want to ... - KOMO News [Last Updated On: July 31st, 2017] [Originally Added On: July 31st, 2017]
- Genetic Testing: Finding the cause of your infertility ... [Last Updated On: July 31st, 2017] [Originally Added On: July 31st, 2017]
- SF's Invitae to acquire two prenatal genetic screening firms - SFGate [Last Updated On: August 1st, 2017] [Originally Added On: August 1st, 2017]
- For Indian doctors, it's written in the genes not stars - Economic Times [Last Updated On: August 1st, 2017] [Originally Added On: August 1st, 2017]