What a mess this has been from the beginning access to testing and now timely testing has been a big nightmare. But there is hope on the horizon.
Testing for COVID is a constant topic of conversation among scientists, patients, the press, politicians and the public. Since the start of the pandemic, and at present, we have been in need of inexpensive, rapid and accurate tests that can be manufactured and distributed widely. Just think if there were an at home test that could be taken 3 times a week. That would certainly help us get back to normal life.
Currently there are multiple tests out there - rapid and not rapid - and it is all very confusing.
First it is important to understand that NO test has been certified by the FDA.
Tests have been given emergency use authorization (EUA) by the FDA, which has allowed tests to be released and marketed during the pandemic after the FDA has reviewed the manufacturer’s testing data. They have not been tested and vetted by the FDA as is usual in non-pandemic times.
There are several testing methodologies now commonly being used, but the current gold standard uses polymerase chain reaction (PCR) technology. This requires a high level of technical expertise, machinery and specific supplies which are quickly being depleted. As many of you know, the test starts with a specimen that is obtained by uncomfortably sampling nasal pharyngeal area with swab which is then put immediately into a buffer for stabilization and inactivation of the virus. The buffer solution is then run through a complex machine where the RNA is first extracted from the virus and then converted into DNA. The DNA is then amplified exponentially by a chain reaction using the enzyme dna polymerase (hence the name). This allows small pieces of genetic material (like small numbers of viral particles) to be amplified, and therefore detected. The machinery to do this is complex and requires operation by a trained technician but results can be obtained in 1 hour. As there has been tremendous demand for testing, there have been bottlenecks in equipment and supplies needed to perform these tests. Therefore turn around time for result has been extremely variable, and sometimes as long as 2 weeks from commercial labs. At New York Physicians we have the capacity to perform the PCR test with results available in a few hours. Please call your doctor to arrange.
Other methodologies have been developed that circumvent these shortages and are being used in some medical settings.
Antigen testing detects certain viral proteins. It is faster and cheaper, can be performed with an anterior nasal (as opposed to nasal pharyngeal swab) It uses supplies that are not running low. In the antigen test material is obtained from the nose and applied to the testing apparatus. Embedded in the apparatus are antibodies specific for a protein in the COVID virus. When a COVID antigen confronts its antibody binding occurs and the apparatus is set up to cause a chemical reaction which can be identified and marked as a positive response. These tests have a quick turn around time, are simpler to perform, involve less complex equipment can be run in doctor’s offices by medical assistant with less training than is needed for PCR assays. These are called point of care tests (POC) and are similar to the rapid flu and rapid strep tests. These are the tests being used by some urgent care clinics. Since the accuracy of these tests are less than that of PCR testing, they are best used for repetitive mass screening. And since specialized equipment is necessary, they cannot be administered at home.
Most recently tests utilizing saliva have been developed. These have great potential for mass testing, as they can be collected in patients’ homes without exposing the testers to potential infection. Currently several companies are offering these as a mail in service for a small fee ($100-150) which may be reimbursed by insurance. The sample is mailed in and a PCR assay is run on the material to try to identify COVID. These tests are accurate, but the drawback is time. A patient must contact the company who may want to do a virtual visit. The collection kit must be mailed to the patient, then it will need to be mailed back to the company. The result is reported in 3-5 days. This is not expeditious enough to help with schools and companies who are trying to screen frequently.
In addition two recent new salivary tests have received FDA EUA approval. One, using a new technique called LAMP (loop-mediated isothermal amplification), can be performed quickly with simpler equipment and gives results in a half hour. This molecular test is being utilized by a few urgent care centers in the city.
Just recently a saliva test using a different assay received FDA EUA approval. Developed privately at Yale, it uses technology that bypasses the nuclear extraction step and reagents that cost less than $10 a sample and are readily available. The salivary collection can occur in any sterile container, avoiding the need for special tubes with specialized buffer. This promising technology is being offered only to high complexity labs across the country.
And, closer to home Dr Zev Williams, an Associate Professor of Women’s Health, has developed a saliva test that is rapid and uses simple equipment and chemicals readily available. The saliva is mixed with a testing reagent in a test tube and incubated at 63C in a water bath. The tube will turn yellow for a positive result and red for negative. The test is awaiting FDA EUA, and will eventually be marketed by Sorrento as Covi-Trace.
Unfortunately the FDA has not yet approved at home testing. Recently these regulations have been loosened, and the hope is that home testing will be allowed soon.
So we are getting there: close to inexpensive, rapid and readily available tests that hopefully can be performed at home, frequently and accurately.
Now wouldn’t that be a game changer?