A 61-year-old woman with osteopenia managed with calcium and Vitamin D supplements and hypothyroidism on levothyroxine comes to a local walk-in clinic after a potential COVID-19 exposure during the holidays. She states that she received 2 doses of the mRNA COVID vaccine but did not receive her booster dose yet. She does admit to attending a large indoor event a couple of days ago and traveling on an airplane during the hectic holiday season. She is having insomnia from the stress of possibly being COVID-19 positive. She is nervous about going back to work and appears anxious especially with the news about how contagious the Omicron variant is and wants to make sure she is not infected. Physical exam is unremarkable and the patient is asymptomatic except that while waiting to be seen, she developed a headache that she describes as a “tight band around my head.” She is very frustrated and confused about all the different tests available for SARS-CoV-2 detection but insists that she want the “best and most accurate test” to detect active infection.
A) SARS-CoV-2 nasal PCR swab
The take home message of this question is the importance of testing asymptomatic individuals who have had recent known or suspected exposure to SARS-CoV-2. Because of the potential for asymptomatic transmission, it is essential that individuals exposed to people with known or suspected COVID-19 be quickly identified. The CDC currently identifies close contacts as people who have been within 6 feet for a combined total of 15 minutes or more during a 24-hour period. This is especially important in people who are not fully vaccinated, as in this patient who did not receive her booster shot. These individuals should get tested immediately when they find out they were in close contact to a known COVID-19 patient. If their test result is negative, they should get tested again 5–7 days after their last exposure or immediately if symptoms develop. Negative test results using a viral test (PCR or antigen) in asymptomatic individuals with recent known or suspected exposure suggest no current evidence of infection. These results represent a snapshot of the time around specimen collection and could change if tested again.
Clinical judgement should determine if an asymptomatic patient gets a negative antigen result and should be followed by a laboratory-based confirmatory PCR test which is the “gold standard” for diagnosis. A PCR test also called a molecular test, detects genetic material of the SARS-CoV-2 virus using a lab technique called reverse transcription polymerase chain reaction (RT-PCR). PCR results may be available in minutes or in a couple of days if analyzed onsite. RT-PCR tests are considered the “gold standard” since they are very accurate when properly performed by a health care professional. An antigen test detects certain proteins in the SARS-CoV-2 virus. An antibody test looks for antibodies that are made by the immune system in response SARS-CoV-2 infection. Antibodies can take several days or weeks to develop after you have an infection and may stay in your blood for several weeks after recovery. This is one reason why antibody tests should not be used to diagnose an active SARS-CoV-2 infection. Also, clinicians and researchers do not completely know if the presence of antibodies directly translates to being immune to COVID-19 in the future. There is no role for chest x-ray and sputum culture in the diagnosis of an asymptomatic patient. Our patient gets a PCR nasal swab and was informed that the results should be available within the hour. While waiting for the results she continues to experience a dull, aching head pain with the sensation of tightness across her forehead with some tenderness in her shoulder muscles. However, once the results return as negative her headache slowly begins to improve.
