COVID 19 Testing - Guide for Physicians

Updated: 4/20/21

Information on COVID-19 testing options and availability is changing frequently. To date, no tests have been approved by the Food & Drug Administration (FDA). But tests are available under Emergency Use Authorization (EUA), which means the FDA has not thoroughly vetted these tests to grant full approval. There is limited information on the efficacy (sensitivity and specificity); a low threshold of detection studies is needed to achieve FDA EUA status. Laboratories developing COVID-19 tests may begin patient testing while their assays are under FDA review. Additionally, there are tests being marketed to physicians that do not have EUA status.

Who Should be Tested for COVID-19?

Family physicians should use their best clinical judgement to determine who should be tested. The CDC has provided guidance on testing for clinicians. This guidance also provides information on the use of tests for surveillance as well as diagnosis. In general, diagnostic testing should be used for:

• Individuals who have symptoms of COVID-19.
• Individuals who have had close contact (within 6 feet of an infected person for a cumulative total of 15 minutes or more over a 24-hour period) with someone with confirmed COVID-19.
• Individuals who have taken part in activities that put them at higher risk for COVID-19, such as travel, attending large social or mass gatherings, or being in crowded indoor settings.
• People who have been asked or referred to get testing by their clinician, state, tribal, local, or territorial health department.

Fully vaccinated people and people who have tested positive for COVID-19 within the past three months with symptoms don't need to be tested. 

Types of COVID-19 Tests Available

Serological (Antibody) Testing - Detects past infection 

Tests detect the presence of IgM and IgG antibodies against SARS-CoV-2, the virus that causes COVID-19.

• Currently, there are several test kits granted Emergency Use Authorization by the FDA.
• The CDC has recently developed its own serologic test that will be used to validate tests from commercial entities and perform surveillance.
• These tests are NOT diagnostic tests and should not be used as such. There is a high potential for false negatives and false positives with these tests. 
• These tests are to be used to show past or present infections, but there is not enough evidence to support that the presence of IgG antibodies to COVID-19 provide short- or long-term immunity to illness, nor whether it reduces the risk of viral shedding in infected individuals.
• These tests are to be used to show past or present infections, but do not confirm the patient has immunity. Some of the tests are not specific enough for COVID-19 infections and will show antibodies for past infections with other coronaviruses. Read the package insert before purchasing.

IgM antibodies are the first to appear and are indicative of a new infection. But it can take days to weeks for these to appear; false negatives can be an issue. False positives are also a concern as there may be cross-reactivity with other coronaviruses. IgG antibodies usually takes at least 4 weeks to appear. These usually show if someone had a past infection but may not be a confirmation of immunity, as they do not measure the effectiveness of a memory response to reinfection. Scientists do not know how SARS-CoV-2 antibodies stay within the body after the infection has cleared.

Molecular Testing (RT-PCR)

Tests used for diagnostic purposes; use reverse transcriptase to create and amplify DNA from SARS-CoV-2 RNA.

• There are now a few molecular tests that are have been classified as waived and can be done as a point of care test. These can be found on the FDA website and are indicated with a “W”. The molecular test is much more specific but false negatives do occur. Use clinical judgement and continue to treat the patient as positive if symptomatic or if there was a known exposure.
• While these tests can detect viral RNA/DNA, they do not distinguish between replicating virus (infectious) and remnants of viral RNA/DNA.

The CDC has developed patient fact sheets  and health care worker fact sheets for the available molecular tests.

NOTE: The FDA has issued an alert that some molecular tests may be impacted by the new variant of SARS-CoV-2, B.1.1.7. View more information.

Antigen Testing

• The FDA has granted EUA to several antigen tests, which detect viral proteins in the nasal cavity. All laboratory settings (high, moderate, and waived) can run this test.
• Antigen tests are relatively inexpensive and can be used at the point of care but are less sensitive than PCR and may result in false negatives.
• Antigen test result interpretation depends on several factors including the stage of infection, performance characteristics of the test (e.g. sensitivity and specificity), and the prevalence of COVID1-9 in the community. The CDC has provided interim guidance  for antigen testing at the individual and community screening.
  - In general, a positive antigen test is most likely reliable given the high specificity of currently available tests
  - A negative test is less reliable due to lower and more varied sensitivity values among the different tests.
  - Negative tests should be considered presumptive and confirmed with RT-PCR when the pretest probability is high and the patient has symptoms or a known exposure.
  -- Confirmation should be done within 2 days if possible.
  -- If PCR testing is not available, patients should isolate.
  
  
• The CDC has provided additional information and an algorithm for use of antigen testing in long-term care facilities (nursing homes). 
   

Point of Care COVID-19 Testing

Rapid COVID-19 tests and those that can provide results for patients in the physician’s office (point of care or POC) are appearing on the market. The AAFP supports POC testing that is accurate and reliable, and encourages physicians to stay informed about the tests offered for COVID-19 as the accuracy and reliability varies.

There are multiple tests that have been granted EUA for use in CLIA-specified laboratories. Three tests are now available for use in family physician offices as outlined above. Additionally, the CDC has provided guidance for POC testing.

At Home COVID-19 Testing

To date, there are several home tests given emergency use authorization by the FDA. Please note that the sensitivity of these tests will vary based on the ability of patients to obtain optimal samples. View more information on sample collection and test results. 

In March 2021, the FDA authorized the first at home test available without a prescription. This test can be purchased in many areas, though costs may vary. 

SARS-CoV2 Proficiency Tests Available
from AAFP Program

CMS/CLIA Laboratory Guidance for COVID-19 Testing

ALERT: Becton Dickinson (BD) Max System has found to produce false positive SARS-CoV2 results. View the FDA's statement to health care professionals. (7/10/20)

Laboratories need a CLIA certificate to perform COVID-19 testing. Under CLIA, laboratories are prohibited from testing human specimens for the purpose of diagnosis, prevention, treatment, or health assessment without a valid CLIA certificate. To become CLIA-certified, laboratories must comply with the accuracy, quality, and reliability requirements as dictated by the statute.

The purpose of these requirements is to ensure that the information that patients or their clinicians receive from a clinical laboratory is accurate and reliable test results. No requirements are being waived in response to COVID-19. However, to expedite access to testing CLIA is allowing for testing to begin once a CLIA number has been assigned as opposed to laboratories waiting for a hard copy paper certificate to come in the mail. 

CMS has provided updated guidance on available tests and the level of lab required for testing.

Reporting COVID-19 Testing

On June 4, 2020, the U.S. Department of Health and Human Services (HHS) announced new guidance for reporting COVID-19 testing. This guidance is pursuant to the CARES Act and impacts all laboratories that are performing or analyzing tests intended to detect SARS-CoV-2 or diagnose possible cases of COVID-19. The goal of this new guidance is to standardize the required reporting information to better monitor disease incidence and trends. Laboratories are now required to report the results from each test to the HHS Secretary of the via existing public health channels to ensure rapid initiation of case investigations. 

For detailed information, see Data Reporting Deadline side bar or the following resources:

• HHS Announces New Laboratory Data Reporting Guidance for COVID-19 Testing
• COVID-19 Pandemic Response, Laboratory Data Reporting: CARES Act Section 18115
• Frequently Asked Questions: Laboratory Data Reporting for COVID-19 Testing

Important Alert for Laboratories Performing COVID-19 Testing

CDC and FDA release Lab Alert: PrimeStore® Molecular Transport Medium (MTM) – an approved transport media for COVID-19 diagnostic swab samples – contains guanidine thiocyanate, which produces a chemical reaction releasing cyanide gas when exposed to bleach (sodium hypochlorite).

The PrimeStore MTM transport media being provided by state health departments is labeled at the bulk box level, but individual vials lack labels and therefore should be handled with caution. Do not use PrimeStore MTM with platforms that include a disinfecting step that uses bleach

For detailed information, see the side bar or the following resources:

• 06/02/2020: Lab Alert: Important Update about Molecular Transport Media (MTM) and Cyanide Gas
• Transport Media Safety Risk - Use Compatible Transport Media with SARS-CoV-2 Tests that Use Bleach - Letter to Clinical Laboratory Staff and Health Care Providers
   

Coding and Billing for COVID-19 Testing

The Centers for Medicare & Medicaid Services and the American Medical Association’s Current Procedural Terminology Editorial Panel are creating relevant codes to keep up with the evolving coronavirus testing environment.

The COVID-19 codes are generalized to capture any technique or target. However, determining the correct code for test procedures can be confusing. This quick reference guide can help you determine the correct code for the test procedure. You can also use the AMA CPT Guidance.