What do we know about using CT scans to diagnose COVID-19?
What do we know about using CT scans to diagnose COVID-19?
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High levels of false negatives from RT-PCR testing and long waits to receive test results have led many medical institutions to use chest CT (computed tomography) scans to diagnose COVID-19. Several studies, mostly conducted in China, have shown higher sensitivity of CT scans in detecting coronavirus when a PCR test showed a negative result. However, this does not mean that CT scans alone should be used for disease identification. CT scans can also miss detecting the virus and be misidentified with other pulmonary infectious/ viral pneumonias. Some experts believe that CT scans do not add any diagnostic value, while others believe that from a population health perspective during a pandemic, CT scans should be used to isolate suspicious cases for COVID-19, because of its high sensitivity and rapid identification. Some studies support a dual approach of CT scans and RT-PCR, or the use of chest CT scan to screen for coronavirus when RT-PCR tests are negative. CT scans are relatively expensive compared to swab tests and also expose patients to a small dose of radiation. Some experts argue that because CT scans are resource intensive, they cannot be used as a population-wide testing tool. The American College of Radiology (ACR) and US CDC recommend against using Chest CT scanning for screening or diagnosis of coronavirus disease 2019. On the other hand, the National Health Commission of China has encouraged the use of Chest CT scans for diagnosis. Local resource constrains and expert physician advise on individual patient conditions are important factors in deciding on the use of CT scans or not.
High levels of false negatives from RT-PCR testing and long waits to receive test results have led many medical institutions to use chest CT (computed tomography) scans to diagnose COVID-19. Several studies, mostly conducted in China, have shown higher sensitivity of CT scans in detecting coronavirus when a PCR test showed a negative result. However, this does not mean that CT scans alone should be used for disease identification. CT scans can also miss detecting the virus and be misidentified with other pulmonary infectious/ viral pneumonias. Some experts believe that CT scans do not add any diagnostic value, while others believe that from a population health perspective during a pandemic, CT scans should be used to isolate suspicious cases for COVID-19, because of its high sensitivity and rapid identification. Some studies support a dual approach of CT scans and RT-PCR, or the use of chest CT scan to screen for coronavirus when RT-PCR tests are negative. CT scans are relatively expensive compared to swab tests and also expose patients to a small dose of radiation. Some experts argue that because CT scans are resource intensive, they cannot be used as a population-wide testing tool. The American College of Radiology (ACR) and US CDC recommend against using Chest CT scanning for screening or diagnosis of coronavirus disease 2019. On the other hand, the National Health Commission of China has encouraged the use of Chest CT scans for diagnosis. Local resource constrains and expert physician advise on individual patient conditions are important factors in deciding on the use of CT scans or not.
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What our experts say
High levels of false negatives from RT-PCR testing and long waits to receive test results have led many medical institutions to use chest CT (computed tomography) scans to diagnose COVID-19. Several studies, mostly conducted in China, have shown higher sensitivity of CT scans in detecting coronavirus when a PCR test showed a negative result. However, this does not mean that CT scans alone should be used for disease identification. CT scans can also miss detecting the virus and be misidentified with other pulmonary infectious/ viral pneumonias. Some experts believe that CT scans do not add any diagnostic value, while others believe that from a population health perspective during a pandemic, CT scans should be used to isolate suspicious cases for COVID-19, because of its high sensitivity and rapid identification. Some studies support a dual approach of CT scans and RT-PCR, or the use of chest CT scan to screen for coronavirus when RT-PCR tests are negative. CT scans are relatively expensive compared to swab tests and also expose patients to a small dose of radiation. Some experts argue that because CT scans are resource intensive, they cannot be used as a population-wide testing tool. The American College of Radiology (ACR) and US CDC recommend against using Chest CT scanning for screening or diagnosis of coronavirus disease 2019. On the other hand, the National Health Commission of China has encouraged the use of Chest CT scans for diagnosis. Local resource constrains and expert physician advise on individual patient conditions are important factors in deciding on the use of CT scans or not.
High levels of false negatives from RT-PCR testing and long waits to receive test results have led many medical institutions to use chest CT (computed tomography) scans to diagnose COVID-19. Several studies, mostly conducted in China, have shown higher sensitivity of CT scans in detecting coronavirus when a PCR test showed a negative result. However, this does not mean that CT scans alone should be used for disease identification. CT scans can also miss detecting the virus and be misidentified with other pulmonary infectious/ viral pneumonias. Some experts believe that CT scans do not add any diagnostic value, while others believe that from a population health perspective during a pandemic, CT scans should be used to isolate suspicious cases for COVID-19, because of its high sensitivity and rapid identification. Some studies support a dual approach of CT scans and RT-PCR, or the use of chest CT scan to screen for coronavirus when RT-PCR tests are negative. CT scans are relatively expensive compared to swab tests and also expose patients to a small dose of radiation. Some experts argue that because CT scans are resource intensive, they cannot be used as a population-wide testing tool. The American College of Radiology (ACR) and US CDC recommend against using Chest CT scanning for screening or diagnosis of coronavirus disease 2019. On the other hand, the National Health Commission of China has encouraged the use of Chest CT scans for diagnosis. Local resource constrains and expert physician advise on individual patient conditions are important factors in deciding on the use of CT scans or not.
Context and background
The 'sensitivity' of a test is its ability to correctly identify a patient with the disease. The sensitivity of RT PCR swab tests is around 50-80%, which means that around 30 to 50% of cases which are actually positive are being missed as false negative (inaccurate result that they are negative, when they are actually positive). Due to the lack of accurate diagnostic testing, infected people and their contacts are not being isolated. CT scans sensitivity is estimated to be over 90% but also has the risk of false positives (result shows positive for coronavirus when it is actually negative).
Physicians in China started using Chest CT scans early in the outbreak because they couldn't rely on the PCR tests fully. They started recommending CT based identification and improved quarantining.
ACR recommends against it citing false-positive rates, scanner contamination and no change in patient management even if the COVID is detected.
The 'sensitivity' of a test is its ability to correctly identify a patient with the disease. The sensitivity of RT PCR swab tests is around 50-80%, which means that around 30 to 50% of cases which are actually positive are being missed as false negative (inaccurate result that they are negative, when they are actually positive). Due to the lack of accurate diagnostic testing, infected people and their contacts are not being isolated. CT scans sensitivity is estimated to be over 90% but also has the risk of false positives (result shows positive for coronavirus when it is actually negative).
Physicians in China started using Chest CT scans early in the outbreak because they couldn't rely on the PCR tests fully. They started recommending CT based identification and improved quarantining.
ACR recommends against it citing false-positive rates, scanner contamination and no change in patient management even if the COVID is detected.
Resources
- Correlation of Chest CT and RT-PCR Testing for Coronavirus Disease 2019 (COVID-19) in China: A Report of 1014 Cases (RSNA -Radiology)
- A role for CT in COVID-19? What data really tell us so far (The Lancet)
- CT scan is a reliable test for COVID-19. Why aren’t we using it? (Lown Institute)
- Sensitivity of Chest CT for COVID-19: Comparison to RT-PCR (RSNA - Radiology)
- Chest CT Findings in Coronavirus Disease-19 (COVID-19): Relationship to Duration of Infection (RSNA - Radiology)
- ACR Recommendations for the use of Chest Radiography and Computed Tomography (CT) for Suspected COVID-19 Infection (American College of Radiology)
- COVID-19 and Imaging: Why CT Scans and X-Rays Have a Limited Role in Diagnosing Coronavirus (UVA Health)
- What is the role of CT scanning in the diagnosis of coronavirus disease 2019 (COVID-19)? (Medscape)
- Covid-19 testing issues could sink plans to re-open the country. Might CT scans help? (Statnews)
- Can CT scans diagnose COVID-19? Experts argue for and against (Medical News Today)
- Correlation of Chest CT and RT-PCR Testing for Coronavirus Disease 2019 (COVID-19) in China: A Report of 1014 Cases (RSNA -Radiology)
- A role for CT in COVID-19? What data really tell us so far (The Lancet)
- CT scan is a reliable test for COVID-19. Why aren’t we using it? (Lown Institute)
- Sensitivity of Chest CT for COVID-19: Comparison to RT-PCR (RSNA - Radiology)
- Chest CT Findings in Coronavirus Disease-19 (COVID-19): Relationship to Duration of Infection (RSNA - Radiology)
- ACR Recommendations for the use of Chest Radiography and Computed Tomography (CT) for Suspected COVID-19 Infection (American College of Radiology)
- COVID-19 and Imaging: Why CT Scans and X-Rays Have a Limited Role in Diagnosing Coronavirus (UVA Health)
- What is the role of CT scanning in the diagnosis of coronavirus disease 2019 (COVID-19)? (Medscape)
- Covid-19 testing issues could sink plans to re-open the country. Might CT scans help? (Statnews)
- Can CT scans diagnose COVID-19? Experts argue for and against (Medical News Today)
