Use of CT scan for testing  Covid is not Correct

Synopsis: The available data and the risk factors suggest that the widespread use of CT scans in diagnosing infectious diseases needs to be sidelined.

Background

• There are mainly three reasons why tests in clinical medicine are performed.
  • Diagnosis: To identify the disease
  • Etiognosis: To identify the causative factor of the disease.
  • Prognosis: To find out the future development of a particular disease.
• In this context, the use of computerised tomography (CT) scans for COVID does not satisfy all the above criteria, for an accurate diagnostic test.

Validation on the effectiveness of CT scan test for Covid

• First, CT scans are not accurate enough to diagnose COVID-19. For instance, according to a study by The Cochrane, CT scan can accurately diagnose COVID-19 in about 88% of individuals with a positive RT-PCR.
  • Since an RT-PCR itself misses 30% of people who have COVID-19, a chest CT is likely to diagnose only 62% of all individuals having COVID-19. It makes it a relatively inaccurate test for diagnosis.
• Second, CT scans are also not accurate enough to identify the causing factor of the disease (Etiognosis). For instance, according to a study by The Cochrane, radiologists have mislabelled 20% of those who did not have the disease as having COVID-19.
  • This has serious consequences on an individual’s health.
    • One, the real causative factor for the disease is left undetected.
    • Two, individuals are subjected to unwanted psychological stress.
• Third, using a CT scan to identify the future course of the Covid disease is also unlikely. For instance,
  • A CT scan can only show the infection in the lungs at that particular point in time.
  • This suggests that a CT is unlikely to give a physician more information than a simple tool such as an oximeter.
• Finally, the risks involved in getting a CT of the chest done are high.
  • According to a study published by The New England Journal of Medicine, in 2007, 4% of all cancers in the United States may be attributed to the radiation from CT studies.
  • Also, apart from the risk caused to individuals, there are risks to radiology technicians, staff, and doctors.
  • Further, there is a high risk of transmission of the virus at such centers. This is because CT scans are needed to be kept in closed air-conditioned spaces.

Way forward

• For diagnosis of Covid, RT-PCR tests, which have higher accuracy compared to CT scans, can be done.
• Individuals should make an informed decision by evaluating the potential risks involved in getting the CT done.
• Further, patients with two negative RT-PCR swabs tests need to be  evaluated for  the possibility of other lung diseases

Source: The Hindu