Image credit: “Pulmonary infarction, right lung Case 209” by Yale Rosen is licensed under CC BY-SA 2.0
This post was reviewed by Dr. Jasmin Chahal, one of our subject matter experts.
The paper that we’re demystifying can be found here, if you want to follow along.
Pneumonia isn’t a fun ride. Defined as an infection of the lungs, pneumonia is a roughly 1 to 3 week-long slog through a high fever, phlegmy cough, chest pain, and sore throat, to name a few symptoms.
The culprits can be bacterial, viral, and even fungal, each with a different flavor of pneumonia. COVID-19 is no exception, so the question must be asked:
What sets nCOVID-19 pneumonia apart from other infections?
The Chinese Center for Disease Control (CDC) team at the frontline of the crisis, in the Anhui province of China, explored this question by monitoring patients with and without nCOVID-19. Researchers worked at the warfront, at Second Affiliated Hospital of Anhui Medical University and Suzhou Municipal Hospital. Selecting patients with pneumonia, they examined 19 COVID-19 and 15 non-COVID-19 patients, from Jan 23 to Feb 5, 2020.
They assessed whether patients had COVID-19 using a lab technique that amplifies and detects one area of the virus’ genetic information, called real-time polymerase chain reaction (RT-PCR). The technique is extremely accurate, able to detect if patients had flu (influenza virus) or indeed COVID-19 (coronavirus). The team used throat swabs as identification samples. A collection of blood tests were performed to understand the details of the pneumonia in a biological context.
From the outside…
Both COVID-19 and non-COVID-19 patients had a fever and cough upon admission. They also both had sore throat and diarrhea as less common symptoms. While there were some COVID-19 outliers, like a case of chest tightness, or two cases of headaches, no significant differences in symptoms were seen. By February 14, none of the pneumonia patients had gone to the ICU, with the exception of two patients, blood oxygen stayed within normal levels.
A peek inside…
The researchers examined patient lungs using a CT Scan, also known as a CAT scan. A CT scan takes a series of 2D X-rays, which can be merged together to form a 3D model of the patient. While X-rays are traditionally thought of to see bones, CT scans can reveal organs and tissues as well.
The CT scan showed that 15 of the 19 COVID-19 patients had evidence of infection in both lungs, compared to only 4 in the non-COVID-19 patients. The hallmark of COVID-19 infections on the CT scans are the appearances of several opaque lobules, small sections of the lung where oxygen normally enters the blood, and carbon dioxide leaves it. In this case, these lobules had “ground-glass” opacity, a term that describes the appearance of glass in a CT scan, suggesting that these lobules were inflamed, and likely couldn’t perform their job. By taking multiple CT scans of a patient over time, researchers noticed that this inflammation spread rapidly through the lobes of the lungs.
CT scans picked up another sign of COVID-19 pneumonia: consolidation. While it misleadingly contains the word “solid,” consolidation means that a segment of lung normally filled with air is now filled with liquid. Seen as a cloudy white area in a CT scan, it also prevents that section of lung from delivering oxygen.
In their blood…
The researchers ran a barrage of tests on the blood samples, looking for differences in specific cells and proteins to find biomarkers: chemicals that let doctors know what a patient has and how they’re fighting it off. In terms of cells, samples from both cases of pneumonia had less lymphocytes and more neutrophils, key cells that defend the body against infection. Though, this result is common in any sort of lung infection.
The distinctions lie in the different proteins from the blood samples. COVID-19 patients had significantly higher levels of three proteins that are known to be biomarkers for liver damage: Aspartate transaminase (AST), Alanine transaminase (ALT), and Gamma-glutamyl transferase (γ-GT). This same type of liver damage occurs in SARS, as well as in severe influenza viral infections. The COVID-19 patients also had abnormally high levels of Lactate dehydrogenase (LDH) and alpha-Hydroxybutyrate dehydrogenase (α-HBDH), biomarkers for general organ damage, suggesting that the liver wasn’t the only organ in trouble.
From the outside, symptoms of COVID-19 pneumonia and pneumonia caused by other infections are nearly identical. However, CT scans and blood samples reveal that the COVID-19 infection can lead to opacities in the lungs, and liver and further organ damage in the rest of the body, which was not seen to be as severe in the non-COVID-19 patients.
But it’s not all doom and gloom. This team’s insight into CT scans and blood anomalies has given us a promising system to identify COVID-19 cases and track its progress. This is a promising study that can then be further developed. For instance, this study should also be done on a various age group, since we know that the young and elderly age group are more at risk of COVID-19 infection. Additionally, the tracking of the patients was only done for 7 days and it would have been more informative to have a study that was done for at least 2 weeks. To be confident that the RT-PCR detects what the authors say, it would have been nice to have the results should be clearly shown in a figure. Additionally, the primers that were used and what area they amplified could have been mentioned so that other researchers that want to perform similar experiments are able to use the same materials and method.
With this article, we have a better understanding of the biomarkers of COVID-19 pneumonia, though the next question is what is causing the level of AST, ALT and γ-GT to raise, while certain lymphocytes and neutrophils are decreased. The virology and immunology behind these results have yet to be understood. Overall, this article presented a lot of new data and allowed us to ask further questions to better understand COVID-19.
Thanks CDC!
