The novel coronavirus designated COVID-19 is quickly becoming a worldwide health emergency. Part of the challenge of containing the virus is in the diagnostic process. Diagnosing patients early enough to prevent them from spreading the virus further has been the issue. A commonly used medical test may be the “secret weapon” in this battle.
Because there are no readily-available drug therapies or vaccines for COVID-19, it’s crucial to diagnose patients in the earliest possible stages. This will allow medical folks to treat a patients symptoms and give them the best chance of beating the disease. But it will also allow another critical function to occur.
The positive-testing patient will be kept from carrying the virus to dozens, hundreds or even thousands of people, thereby making a bad situation worse.
What’s the medical test that is coming to the diagnostic rescue in the fight against COVID-19? The humble computed tomography scan (CT scan,) often referred to as a “CAT scan.” (Though no actual cats are involved.)
A recent study of over 1,000 patients stated that the CT scan should replace lab testing as the primary screening tool for COVID-19. In the study, published in the journal Radiology, the CT scans outperformed lab testing for early detection of the virus.
Currently, the Chinese medical community is using reverse-transcription polymerase chain reaction (RT-PCR) or gene sequencing for blood or respiratory samples as the diagnostic method. With this process, they are establishing who should be hospitalized and who shouldn’t.
RT-PCR is complex and has limitations. Sample collection and transportation are issues, as well as the performance of the RT-PCR kits. The results are not reliable or sensitive enough and it’s impossible to test everyone in a timely manner. That leaves a large number of people walking around with the virus.
Given the highly contagious nature of COVID-19, there needed to be a better way to screen large numbers of potential patients quickly and more accurately. Currently the R0 rate, or rate of multiplied infection spread, is 3,28. That means every person with COVID-19 will infect more than 3 people, on average. At that rate, the virus could overwhelm even the American medical system in a matter of weeks.
Next week, I’ll be writing about what you really need to know about coronavirus COVID-19, as well as some of what you haven’t been told. I’m on it and I’ll share what I’ve found with you.
For now, the discovery that CT scans are more effective at identifying COVID-19 patients is very good news. According to the study authors: “Early diagnosis of COVID-19 is crucial for disease treatment and control. Compared to RT-PCR, chest CT imaging may be a more reliable, practical and rapid method to diagnose and assess COVID-19, especially in the epidemic area,”
Chest CT is a routine medical imaging tool for diagnosing pulmonary illnesses like pneumonia. It’s fast, relatively easy to perform and non-invasive. It doesn’t require throat swabbing and is available at thousands of facilities in North America.
Even better, the sensitivity rate of CT scans for detecting COVID-19 is 98%. The sensitivity rate for RT-PCR is just 71%. That means significantly more accurate diagnoses at a faster rate.
The initial study, which is currently being followed up on here in America, was performed by researchers at Tongji Hospital in Wuhan, China. Wuhan was the epicenter of the outbreak and has more COVID-19 sufferers than any other city in the world right now.
Doctors included 1,014 patients in the study. Each had both chest CT scans and RT-PCR tests performed between January 6 and February 6, 2020. The performance of chest CT scanning was assessed by using RT-PCR as a reference standard. Some patients had multiple RT-PCR tests done during that period. Researchers reviewed the dynamic conversion of RT-PCR test results (negative to positive and positive to negative) in comparison with serial chest CT scans.
The results showed the CT scans superiority pretty clearly. 601 (59%) patients had positive RT-PCR results, with 888 (88%) having positive chest CT scans. The sensitivity level of the chest CT scans in recognizing COVID-19 was 97%, based on the positive RT-PCR results.
What might be more interesting is that for patients who had negative RT-PCR results, a whopping 75% (308 out of 413) had positive chest CT scan results. 48% of those people were considered highly likely to have COVID-19, while 33% were considered probable.
By analyzing the serial RT-PCR assays and chest CT scans, researchers were able to determine that the interval between the initial negative to follow-up positive RT-PCR results was 4 to 8 days.
That means that a patient tested with RT-PCR might be positive, but not test as such. 4 to 8 days later, they would test positive. During that time, they mat have been positive. As a result, they may have been spreading the virus. If a CT scan had been the initial diagnostic tool, that period of disease spread could have been eliminated.
“About 81% of the patients with negative RT-PCR results but positive chest CT scans were re-classified as highly likely or probable cases with COVID-19, by the comprehensive analysis of clinical symptoms, typical CT manifestations and dynamic CT follow-ups,” the authors wrote.
We may not have a vaccine yet. We may not have determined which anti-virals or other drugs are effective in stopping the virus once someone has it. But we seem to have found a more accurate, more widely available and simpler tool for diagnosing COVID-19. Is this the “secret weapon” many are hoping for? Maybe on the diagnostic front. Time will tell.
Keep the faith and keep after it!
Related Content –
Material Source – Radiological Society of North America
Journal Reference – Tao Ai, Zhenlu Yang, Hongyan Hou, Chenao Zhan, Chong Chen, Wenzhi Lv, Qian Tao, Ziyong Sun, Liming Xia. Correlation of Chest CT and RT-PCR Testing in Coronavirus Disease 2019 (COVID-19) in China: A Report of 1014 Cases. Radiology, 2020; 200642 DOI: 10.1148/radiol.2020200642