Clinical Guidance for Recovered/Previously Positive COVID-19 Patients

Research shows many individuals who recover from COVID-19 may continue testing positive for the virus for weeks to months, despite no longer being contagious. We have seen this phenomenon in our own patients and employees and it has raised a number of questions we want to provide additional guidance on, including:

What is a “symptom-based release from isolation”?

The symptom-based strategy is a process by which confirmed COVID-19 patients are deemed to not be contagious and are cleared from isolation or other transmission-based precautions. It is based on the duration of time from the initial diagnosis (symptom onset or positive test) in combination with the resolution of fever for at least 24 hours (without using any fever-reducing agents) and improvement of COVID-19-related symptoms. The amount of time needed for an individual to no longer be contagious varies by immunosuppressed status and illness severity as described in the chart below. Clearance from isolation for asymptomatic individuals is only based on time from initial positive test. 

The rationale and research behind these recommendations are summarized in the following Centers for Disease Control and Prevention (CDC) decision memo.

How can a patient have a positive PCR test but not be infectious?

Reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR) is the primary method used to diagnose SARS-CoV-2 infection and many other viruses. The test works by creating copies of viral genetic material in respiratory samples over many cycles. A single copy of viral RNA can be amplified to more than 2 trillion copies during a typical 40-cycle testing protocol. Amplification of genomic sequence is measured in cycle thresholds (Ct) and the Ct values correlate with whether a sample contains infectious virus particles. If the viral RNA is detected after just a few amplification cycles (i.e. at a low Ct value), that means high RNA levels are present and thus more viable virus; however, because this test is designed to be a sensitive diagnostic tool (not for monitoring disease progression), a very high Ct value (low RNA level) is set as a positive range cutoff. This means that very low levels of the RNA or viral genomic fragments can test “positive” for months after the acute infection but are not associated with live virus. This detection issue is common for other RNA viruses.

PCR is very sensitive and used to extract genetic material from samples embedded in paraffin and other inactivating substances as well as from ancient fossilized samples. In the case of SARS-CoV-2 (and other viral infections), the RNA fragments persist after symptoms resolve and can be detected for up to three months. 

RT-qPCR testing has been validated against tests to see if there is live virus present that can be grown in culture (i.e. replication competent virus). Several studies have shown that patients with mild to moderate disease have no viable virus cultured eight days after symptom onset. For patients with severe illness, and in those who were immunocompromised, virus was cultured for up to 20 days after infection onset, although at 15 days only 5% still had cultures that grew.

When can a patient who tests positive for COVID-19 discontinue transmission-based precautions?

UT Southwestern recommends a symptom-based strategy for discontinuation of isolation precautions. COVID-19 positive individuals must meet the days since diagnosis/symptom onset requirements, be afebrile, and have improved symptoms, as outlined in the table below.

Confirmed COVID-19 Positive or Clinically Suspected Positive

 

Immunocompromised Patients  

Invasive Mechanical Ventilation (current)

ICU Level Care (current or prior)

All Other Symptomatic Outpatients

or Inpatients

Asymptomatic

Minimum Number of Days since diagnosis & symptom onset

28 days

20 days

20 days

10 days

10 days since 1st positive test

Absence of Fever without antipyretics

>24 hours

>24 Hours

>24 Hours

>24 Hours

-

 

Symptoms

Symptom improvement

Clinically stable

Symptom improvement

Symptom improvement

-

 

Testing

No testing

No testing

No testing

No testing

No testing

What if a patient who previously had COVID-19 has a subsequent scheduled outpatient appointment, surgery, or procedure?

Patients who have recovered from COVID-19 must meet the symptom-based criteria above and pass the pre-visit infection risk screen before arriving for any outpatient visit, procedure, or surgery.  Patients who remain febrile and require a procedure/surgery that cannot be delayed without adversely affecting the patient will need to be reviewed with the Chief Medical Officer and Infection Prevention so that appropriate guidance can be provided. Previously positive/recovered individuals do NOT need to be tested pre-procedure for at least 90 days after their initial positive test. After 90 days these patients may be retested if they become symptomatic.

When an inpatient tests negative for COVID-19 via PCR test, how long is the negative result considered credible?

Because the risk of hospital transmission is low, a negative COVID-19 PCR test is valid or “credible” for the duration of the patient's hospitalization. However, the incubation time from exposure to symptom onset can be as long as 14 days and a second COVID-19 test should be performed if new symptoms develop while the patient is in the hospital.

Are there any exceptions to the 72-hour window for presurgical/pre-procedural testing? What if patients had COVID-19 testing at UTSW prior to 72 hours by a few days?

There are no exceptions to the 72-hour testing window. If an individual underwent testing as part of a COVID-19 exposure, their procedure should be rescheduled accordingly.

Should a patient who has been exposed to COVID-19 but is currently at home and asymptomatic be tested? 

If the patient is fully vaccinated and has had close contact with someone who has COVID-19 they should get tested 3-5 days after exposure, even if they don’t have symptoms. They should also wear a mask indoors in public for 14 days following the exposure or until testing returns negative.

If the patient is unvaccinated, testing within 3-5 days post-exposure may be considered for patients who have been exposed to COVID-19 and are asymptomatic. They should continue to self-quarantine for a period of 14 days as a single negative test at that timepoint does not exclude the possibility of infection developing later in the incubation period. The decision to test and/or quarantine health care workers with COVID-19 exposures is determined by Occupational Health.