Can CT scans diagnose COVID-19? Experts argue for and against

In addition to RT-PCR testing, some experts argue that CT scans can diagnose COVID-19. Others disagree. Medical News Today spoke to two doctors who present their opposing viewpoints.

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As the COVID-19 pandemic continues to claim lives across the globe, early diagnosis of people with SARS-CoV-2 is essential. Once a person has received a diagnosis, limiting their physical contact with others is one way to slow the spread.

What is the best way of establishing a firm diagnosis for COVID-19?

For many, the use of reverse transcriptase polymerase chain reaction (RT-PCR) is the gold standard. This molecular biology technique detects genetic material that is specific for the SARS-CoV-2 virus. Yet, RT-PCR is not 100% accurate, and some experts have raised questions around false-positive and false-negative test results.

Could computed tomography (CT) scans, which combine a series of X-ray images, serve as an alternative or an adjunct to RT-PCR diagnosis?

There have been reports from Wuhan in China of healthcare professionals using CT scans to diagnose COVID-19, yet medical and public health bodies in the United States have not followed suit.

Medical News Today spoke to two doctors on opposing sides of the argument around the use of CT scans during the pandemic.

Arguing for the use of CT is Dr. Joseph Fraiman, M.D., an emergency doctor working in the New Orleans area, LA, and a former Medical Manager for Lousiana’s Disaster Task Force 1 Urban Search and Rescue Team.

On the opposing side is Dr. Mark Hammer, M.D., from the Department of Radiology at Brigham and Women’s Hospital, Harvard Medical School, in Boston, MA. He writes on behalf of a group of doctors who recently published a viewpoint article on this topic in The Lancet.

Dr. Fraiman: The American College of Radiology (ACR) and the Centers for Disease Control and Prevention (CDC) have recommended against routine use of CT scans to diagnose COVID-19.

However, in China, where experts quickly and effectively controlled the disease, professional medical organizations universally agree that CT plays “a vital role in early detection, observation, and disease evaluation.”

The ACR recommend against CT scans based on false-positive rates, scanner contamination, and a lack of change in individual patient management.

However, Chinese experts strongly recommend CT based on rapid identification, improved quarantining, and tailored public health measures.

Why such opposing views?

Early on in the COVID-19 outbreak, it became clear that RT-PCR testing is both slow and unreliable. One Chinese official estimated that swab test sensitivity was as low as 30%, a finding consistent with RT-PCR testing of fluid samples.

More optimistic estimates from the ACR suggest a range of 42–71% for the RT-PCR test. In other words, the swab misses nearly a third of cases — at best.

According to a research article in Radiology, CT is far more sensitive, commonly detecting cases the swab misses. CT’s higher sensitivity (routinely estimated at well over 90%) and real-time results come at the expense of increased false-positives.

But this downside is of far less concern to public health authorities than poor sensitivity. The World Health Organization’s (WHO) strategic objective to stop human transmission of SARS-CoV-2 prioritizes the detection and isolation of potential spreaders above all else.

For the benefit all

This focus on sensitivity, even at the cost of false-positives, reflects the goals of pandemic medicine. Typically, doctors use diagnostic tests to benefit individuals, but the calculus of testing changes in epidemics.

Experts in nations that endured SARS learned the hard way that rapid, sensitive testing is critical during an infectious outbreak not because it benefits individuals, but because it benefits everyone.

The focus of American experts on individual case management is well-intentioned and morally laudable — usually. But the same logic quickly becomes dangerous during an epidemic. In transitioning to pandemic thinking, nations such as China saw that over-diagnosing COVID-19 was far better than under-diagnosing.

You can’t fight what you can’t see, and CT scans are the best way to see the disease. If false-positives occur, the ‘penalty’ is typically home quarantining additional people who are actively ill with another lung infection.

Moreover, the reason to diagnose COVID-19 is not ‘patient management,’ it is pandemic management. The scans are not for the benefit of the person having the scan; they are for everyone else.

Detecting disease and quarantining is how we keep people without the infection safe. In other words, aggressively finding disease and isolating positives halts transmission, potentially saving not just one life, but many.

As for scanner contamination, China has no monopoly on cleaning techniques or technology. Their cleaning protocol allowed for the safe scanning of 200 patients each day on a single scanner with multiple clinics documenting zero transmissions to CT suite staff.

This was one of many integral and necessary adaptations that yielded inarguable success. Their curve swiftly flattened, which saved countless lives.

Rapid results lead to false-negatives

Now, with the emergence of a rapid RT-PCR test, there is cause for new fear. In the excitement generated by finally achieving swab results as quickly as CT scan results, providers and authorities could forget how dangerously inaccurate the PCR test is.

Rapid results mean rapid false-negatives and rapid false reassurance. This also means the rapid release of people with COVID-19, allowing them to mingle with people without the infection who may be potentially vulnerable.

Using both tests together would increase sensitivity and improve quarantine efficacy, an impact neither could achieve alone.

The ACR and other organizations have raised concerns that CT scans “may result in false-negative cases, and the risk of missing COVID-19 has broad implications.”

This is a perplexing statement. While the rushed literature we must use to inform COVID-19 testing is methodologically flawed, there is little dispute about whether CT is more sensitive—it is, and the ACR acknow