Should you get a CT scan to test for COVID-19? Here’s what the research says
If you haven’t already gotten tested for the coronavirus by now, you’ve probably at least heard of the drill. A nurse sticks a long, pointy swab deep into your nose (although it might as well be your brain for what it feels like) and moves it around to gather the sample. Once the test is done, it takes around 20 minutes for the vague pain in your sinuses to fade and anywhere from 24 hours to 2 weeks for your results.
This is the well-known swab test, or PCR (polymerase chain reaction) test, and it can tell you whether or not you have COVID-19 in your system at that particular moment. If you’ve been exposed to someone with the virus, if you’re asymptomatic, or if you simply want some peace of mind, the PCR test is extremely useful. Advantages include that it’s quick (takes around 30 seconds to administer), cheap (or free, in some places!), and in the ideal world, have very high accuracy.
However, in the real world, PCR tests are not perfect, for practical reasons. Not all administrators insert the swab deep enough to obtain a good sample, which could lead to false negatives. A person getting tested too early or too late can produce an inaccurate result as well. In addition, since most clinics have a backlog of tests, it could take weeks to get the results, rendering the test you took effectively meaningless. Finally, PCR tests only tell you whether you have coronavirus or not — it can’t tell you the severity or internal symptoms you may have.
So can we get a better picture? Researchers have been looking into CT scans as a way to assess COVID-19, on the basis that it produces fast results and is more widely available than PCR tests. Specifically, chest scans could display internal features of COVID-19 pneumonia, including ground-glass opacities in the lungs. One early study of 1014 cases in China reported a 97% sensitivity rate for CT imaging — that is, 97% of people who tested positive on the PCR test also showed abnormal chest scans.
Additionally, CT scans may also provide insight into the progression of the disease. This study found that there was a “significant difference” in the pulmonary manifestations displayed on the scans between the first and second week after onset of symptoms. A CT scan could be useful to track the course of the virus in a patient with significant respiratory symptoms, and identify any abnormalities that could indicate future worsening.
That being said, the use of CT scans for COVID-19 diagnosis has been challenged. Raptis et al. argues that the sensitivity rates of the scans has been overestimated, and points out that the lung abnormalities associated with COVID-19 pneumonia are also present in a host of other respiratory infections. Therefore, CT scans on their own aren’t enough to confirm you have coronavirus — they’re most reliable as a supplement to a positive PCR test. There is also the very real hazard of contagion with imaging equipment and air transmission inside the hospital, putting healthcare providers at risk.
So: Should you get a CT scan if you suspect you have coronavirus? As a first step, the best thing to do is get your PCR test. From there, you can decide whether your respiratory symptoms and risk factors necessitate a CT scan. Here are the Fleischner Society for thoracic radiology’s recommendations on the use of imaging for COVID-19:
Imaging is not indicated as a routine screening test or for patients with mild features of COVID-19.
Imaging is indicated for patients with moderate to severe features of COVID-19 regardless of COVID-19 test results.
Imaging is indicated for patients with COVID-19 and evidence of worsening respiratory status.
For a second opinion, talk to your doctor. If you’re not in a place where a doctor is available or you’re not comfortable with going to the hospital, CureAssist offers tele-consultations with top radiologists from the comfort of your home. Download the app here.
Until then, remember to wear a mask, wash your hands, and stay safe!
This article was written by Rithana Srikanth.
