COVID-19 Retesting in the Primary Care Setting

Abstract

Primary care providers (PCP) play an essential role in preventing transmission of COVID-19 by determining when patients should discontinue home isolation and return to work. Current Centers for Disease Control and Prevention guidelines addressing such decisions include (1) non-test-based strategy, which advises that patients may discontinue home isolation after at least 72 hours have passed since recovery (defined as resolution of fever without use of fever-reducing medications) and improvement in respiratory symptoms and at least 7 days have passed since symptom onset or (2) test-based strategy, which advises resolution of fever and improvement in respiratory symptoms and negative results of an FDA Emergency Use Authorized molecular assay for COVID-19 from at least 2 consecutive nasopharyngeal swab specimens collected ≥24 hours apart.1Centers for Disease Control and PreventionCoronavirus Disease 2019 (COVID-19). Discontinuation of Isolation for Persons with COVID-19 Not in Healthcare Settings (Interim Guidance). CDC Website, 2020Google Scholar In some instances, more stringent criteria are warranted to reduce the risk of transmission in settings where a patient may be returning to work at a transportation hub or healthcare setting. Repeat testing in the convalescent period is typically advised in patients entering a congregate setting after hospitalization.2McMichael T.M. Clark S. Pogosjans S. et al.COVID-19 in a long-term care facility — King County, Washington.MMWR Morb Mortal Wkly Rep. 2020; 69 (February 27–March 9, 2020): 339-342http://dx.doi.org/10.15585/mmwr.mm6912e1Crossref PubMed Google Scholar PCPs often encounter scenarios where these recommendations do not provide sufficient guidance. For example, we recently encountered a case of SARS-CoV-2 prolonged viral shedding in an ambulatory patient. This 34-year-old man without chronic medical problems or prescribed medications presented to his PCP with a dry cough, fever, anosmia, ageusia and diarrhea of 4 days duration and tested positive by molecular assay for COVID-19 from nasopharyngeal swab. After 3 weeks, the patient reported resolution of all symptoms except cough, which was diagnosed as post-viral cough. Because the patient worked at the airport, he sought medical advice before returning to work. Due to ongoing cough, repeat molecular assay for COVID-19 from nasopharyngeal swab was performed and was found to be positive. This case poses many challenges to the PCP. What does a positive COVID-19 test tell us at this stage? Can the patient return to work or remain on home isolation? When should the test be repeated? Although a positive molecular test result may not correlate with viral load or infectivity, it seems reasonable to assume that patients with prolonged cough may aerosolize virus and transmit infection even if viral loads in the upper airways are low. This is supported by emerging data demonstrating that viral clearance can be delayed in samples collected from lower airway, stool and nasopharyngeal swabs.3Young B.E. Ong S.W.X. Kalimuddin S. et al.Epidemiologic features and clinical course of patients infected with SARS-CoV-2 in Singapore [published online ahead of print, 2020 Mar 3].JAMA. 2020; e203204https://doi.org/10.1001/jama.2020.3204Crossref Scopus (1323) Google Scholar Indeed, certain populations, such as those immunocompromised, pregnant and advanced age individuals, are known to be at risk for prolonged viral shedding.4Ogimi C. Greninger A.L. Waghmare A.A. et al.Prolonged shedding of human coronavirus in hematopoietic cell transplant recipients: risk factors and viral genome evolution.J Infect Dis. 2017; 216: 203-209https://doi.org/10.1093/infdis/jix264Crossref PubMed Scopus (47) Google Scholar Reports have shown that some patients shed virus for weeks or even months.5Liu W.D. Chang S.Y. Wang J.T. et al.Prolonged virus shedding even after seroconversion in a patient with COVID-19 [published online ahead of print, 2020 Apr 10].J Infect. 2020; (S0163-4453(20)30190-0)https://doi.org/10.1016/j.jinf.2020.03.063Abstract Full Text Full Text PDF Scopus (171) Google Scholar Further, PCPs must evaluate the risk of transmission when considering retesting in patients with ongoing symptoms since current guidelines do not indicate this is necessary. And, guidance will be needed on whether retesting should be performed in asymptomatic individuals at high risk for prolonged viral shedding. To date, testing guidance has prioritized hospitalized patients and health care workers in order to allocate and conserve limited test kits and personal protective equipment. As more resources become available, we anticipate liberalization of testing to include retesting in (a) those with symptoms suggestive of prolonged viral shedding and (b) those asymptomatic yet at increased risk for prolonged viral shedding. We note that there are individual differences in rate of recovery, viral clearance, as well as the risk of forward transmission. PCPs are strategically poised to consider all factors and determine the best course of action. Given the absence of guidelines, for our patient who worked in the public transit industry, we recommended continued home isolation and repeat molecular testing in 1 week, with negative results permitting a return to work.