What is a RT-PCR Nasal Swab Test?
RT-PCR is a method of testing to detect presence of virus using well-established recombinant RNA technology. Taking a sample from nasal or oral passage is one of the ways to do this. The RT-PCR for SARS-CoV-2 was authorized under emergency use by the FDA. Repeat RT-PCR swab testing may be needed if there is a negative result in a person who is at high-risk due to “false negative” result possibility by nasal or oral swab technique. RT-PCR requires advanced testing equipment to process in a formal lab. Results may be available anywhere from one to several days. Despite issues, it is considered the test for diagnosing or confirming Covid-19 virus at this time. The RT-PCR uses RNA to detect virus presence.
Antibody or Serology Testing for Covid-19
- When exposed to a pathogen the body mounts various responses to counter its effects. Forming neutralizing antibodies is one of the ways in which a person fights infection. There are many types of antibodies in the body. For Covid-19 resulting from SARS-CoV-2 virus, two antibodies are of interest: IgM and IgG. IgM is a form of an antibody that rises in blood when it is exposed to a virus early in the course of disease. This rise can be checked to indicate if you have been exposed. There can be negative IgM test result depending on how long has passed since the person was exposed to the virus. Typically, it can lag anywhere from couple days to a week or longer depending on a person’s immune status and amount of viral exposure. It tends to correlate with symptoms in Covid-19 virus but may also be found in people who are without symptoms. Like IgM, IgG too is an antibody. It usually does not appear in the body until much later in the disease process. It can take 3 weeks or longer before IgG response can be measured. IgG is the antibody that correlates with past exposure and possible longer-term immunity. It is unclear currently, however, if IgG confers long-term immunity in Covid-19. Both antibodies can be used for indirect assessment of a person’s exposure to SARCoV-2 and immune response.
- There are two methods currently to check for Covid-19 related antibodies:
- Rapid (fingerstick or venipuncture) IgM antibody test for SARS-CoV-2. Preliminary result in 10-15 mins. It is used for screening or surveillance only at this time. If positive and depending on clinical situation, person will need further RT-PCR testing for confirmation and diagnosis of Covid-19
- Rapid (fingerstick or venipuncture) IgG antibody test for SARS-CoV-2. Preliminary result in 10-15 mins. It is used for surveillance of exposure and long-term immune response presence. It may need additional confirmation with blood serology of IgG and/or RT-PCR for diagnosis if clinically warranted.
- NOTE: The rapid antibody test is generally sensitive and specific for SARS-CoV-2 depending on “testkit” being used. The accuracy tends to be better the further time has passed since exposure or symptom onset. Further testing will be required with RT-PCR swab testing for diagnosis or blood serology correlation. There are different rapid test kits available of different types, many are under FDA review for emergency use authorization and are authorized for use only during Covid-19 emergency by medical professionals and labs as per CDC or FDA guidelines. Although part of a larger coronavirus family which includes SARS and MERS, SARS-CoV-2 that causes Covid-19 is a new (‘novel’) virus, and, as such, there are no prior tests to use to diagnose it. Accuracy on these test options do vary, and so, clinical judgment is needed to guide the patient. All Covid-19 tests have limitations and there is always a possibility of situations where a person may be false negative (meaning, you have Covid-19 but tested negative) or false positive (meaning, you tested positive but do not have Covid19). It is because of this we recommend a clinical screening process and decision by licensed provider.
- Blood draw for Direct Measurement of IgG serology in a lab. IgM lab serology is not yet available. IF positive for IgG on blood serology, you may be a potential donor of plasma for Covid-19 patients!
- Other tests: rapid antigen swabs, saliva-based PCR, stool sampling, sewage tests and other approaches are being evaluated.=
What can I expect? In all scenarios, prevention is warranted as per CDC guidelines and state/federal regulations. Here are some examples of test results and what they can mean:
- If you are IgM positive on the rapid test, you may need to self-quarantine, especially if you are having symptoms and depending on how long since exposure or symptoms. You will need RT-PCR test for diagnosis of Covid-19.
- You may be RT-PCR positive and not have any antibody response. This can happen if you are early in the disease process or not enough viral exposure to trigger an immune response. If positive on RT-PCR, you may have active disease and/or are a carrier with or without symptoms. You are considered contagious and possibly infected. Must complete 14-day quarantine and/or as determined by clinician and as per CDC guidelines regarding quarantine and prevention
- You may be RT-PCR negative and IgM/IgG negative, which might mean you do not have active disease or exposure at this time. You may yet need repeat testing if high risk group and if clinically warranted for further assessment.
- You may be IgG positive only, which could mean you were exposed and mounted a long-term response. This does not rule out active Covid-19 carrier state or ongoing active infection; this can only be known by RT-PCR testing.
- There are several other scenarios like these, and it will depend on your exact clinical condition and provider evaluation.
- If this is part of your return to work or employment monitoring program for Covid-19, then there may be additional requirements. Check with your employer.
- 'It is always good to maintain adequate hydration and nutrition during an illness and avoid getting dehydrated. You can consider taking extra supplements, such as Vitamin C, Zinc or other elements and vitamins. However, excessive use can be problematic. Always consult with your primary care provider if such remedies and supplements are appropriate for you. If you are diagnosed with or suspected to have Covid-19, it is extremely important to avoid unnecessary contact with others and maintain continuous preventive measures. If you are having symptoms, then monitor yourself closely; if worsening, contact your medical provider as soon as possible and/or seek help at your nearest medical facility.
ALWAYS FOLLOW PREVENTIVE MEASURES: Mask, Physical Distancing, and Frequent Hand Washing!!!
CDC Guidelines: https://www.cdc.gov/coronavirus/2019-ncov/index.html