Diagnosing COVID via CT scan

Coronavirus disease – 2019 is abbreviated as COVID-19. The name of this disease is based on its causative agent, which is a novel SARS virus of the coronaviridae family. In the past 3 years, this virus has affected and killed hundreds of millions of people, across the globe. It is a respiratory infection that predominantly affects the chest, nasal cavity, throat, and lungs, and within a few days, the infection progresses towards the cardiovascular system, muscular system and bones. 

COVID-19 pathophysiology 

Genome: The coronavirus 

The coronavirus is the RNA virus with a positive sense of genome size 30 Kb. The subfamily of coronavirus is orthoviridae which contains 4 genera.

1. Alphacoronavirus
2. Betacoronavirus
3. Deltacoronavirus
4. Gammacoronavirus

The viral infection to the host largely depends on viral surface proteins. The isolated protein content of SARS-CoV-2 has been characterized into 4 types of proteins: 

1. Spike proteins host
2. Enveloped proteins
3. Membrane proteins
4. Nucleocapsid proteins

Spike proteins are responsible for giving the spikes like structure on the surface of coronavirus. These spike proteins provide a distinguishing feature to this virus as compared to other viruses. Additionally, the spike proteins are the majorly responsible for the initial stage of viral infection in the human cell, because these proteins firmly bind to the human receptors and then the genome is transferred to the human cell body. 

Host receptors that binds SARS virus

SARS-CoV 2 infects the host cells by binding through its spike proteins. These spike proteins possess 2 subunits (S1 and S2). The S1 spike domain binds to the specific host cell receptors, which include,

1. TMPRSS2 – Transmembrane protease- serine 2
2. ACE2- Angiotensin-converting enzyme 2 

Both of the receptors have some chemical and molecular interaction with spike proteins. These receptors are found on the surface of mucosa cells and epithelial cells of the following body locations:

1. Oral mucosa (predominantly)
2. Lungs (predominantly)
3. Heart
4. blood vessels
5. Intestine
6. Kidney
7. Bladder
8. Brain 

Consequently, these are the locations that are most prone to viral attack and so, these are the target sites for diagnosis. 

According to the studies, initially, RT-PCR or real-time polymerase chain reaction is the gold standard set to diagnose COVID-19 by examining the samples obtained from the oropharyngeal region of the respiratory tract. However, various controversies arise on the reliability of this test due to repeated false positive and negative results obtained in different laboratories for the same case. Realising this situation, the health professionals provided various other alternatives to get assured diagnosis for this viral disease. One of the tests is computed tomography to scan the chest region of the body. The CT scan is a rapid test (hardly take 40 minutes to get a complete scan) for COVID-19 pneumonia suspected patients. According to the comparative studies on effectiveness and reliability of both the tests (CT scan and RT-PCR), CT scan proved to be a highly reliable and rapid screening tool. For this purpose high resolution computed tomography is employed. The chest HRCT scan images have comparatively high potential for the prediction of clinical outcomes of SARS- COV 2 patients. Hence, CT scan has proved to be an essential diagnostic tool for the management of COVID -19 affected individuals. 

CT scan, a reliable test over RT-PCR

Researchers and medical practitioners claimed various reasons for preferring CT scan over RT-PCR to get a reliable diagnosis. Some of their concerns include, 

1. In RT PCR, the sample size is quite small, consequently, the chances for false positive results will increase eventually.
2. Lack of information regarding the scoring system set to quantify the extent of lung involvement during the infection.
3. RT PCR can provide results of 100s to 1000s of samples at the same time, though this is quite helpful while testing masses but when it comes to individual examination, cross-examination is always required as there can be chances of errors like sample exchange. Whereas, in the case of a CT scan a patient is examined individually. Hence, there are no chances of mixing reports.

Damage to lungs in COVID-19

In simple terms, COVID-19 infection damage the lining of the lungs, more precisely we can say the walls of the alveoli of the lungs get adversely affected which lead to breathing problems, and when the infection progress further it infects the blood vessels, resulting in lung failure, which is termed as acute respiratory distress syndrome.

Post-COVID consequences

COVID-affected people exhibit various other symptoms and diseases, which include, 

Common symptoms

1. Tiredness2.

2. Fatigue

3. Fever

4. Loss of smell

5. Loss of taste

6. sore throat

7. red or irritated eyes

8. Skin rashes

9. headache

10. diarrhea

11. discoloration in fingers and toes

Respiratory and heart symptoms

1.Shortness of breath

2. Cough

3. loss of speech

4. Loss of mobility

5. confusion

6. Chest pain

7. heart palpitations – fast heartbeat or pounding

Cognitive symptoms

1. Brain fog- concentration issues and thinking problem
2. Sleep problems
3. Headache
4. Lightheadedness- morning dizziness
5. Twitching or needles poking
6. Change in smell or taste
7. Depression
8. Anxiety that persists

Stomach related symptoms

1. Diarrhea
2. Stomach pain

Other symptoms

1. Joint or muscle pain
2. Irregular menstruation

CT scan score for covid out of 25

CT scan severity score is employed to assess the severity of infection, which is th sum total score out of 25, this is the standard set to categorize the infection into 

1. Mild
2. Moderate
3. Severe

The COVID infection is diagnosed as mild when the severity score is less than 7. 

Moderate infection refers to the diagnosed score between 7-18, at this stage the symptoms are more severe than mild infection.

If the severity score is found to be higher than 18 then, the person’s infection is categorized in severe type.

FAQ’s

How CT Scan works?

In computed tomography, ionizing radiations or X- rays are directed at an object or internal organ of the body across multiple orientations. The signals are detected with a built-in electronic detector which measures the resulting pattern of densities along a series of linear paths and transmits these signals to produce images. As this technique involves scanning a particular body, it is called CT scan or computerized axial tomography.

CT scan for covid cost ?

A high-resolution chest CT scan in India can cost you around   ₹ 2,000- ₹ 6,500.

Is undergoing a CT scan risky?

A computed tomography procedure is not a painful diagnostic test. However, it may be risky for some people or under some conditions. 

1. Risk to unborn babies: Radiations of CT scans are of a very low dose, that does not harm humans. However, if a woman is pregnant, she might inform her doctor of her so that her doctor can recommend alternative diagnostic techniques like magnetic resonance imaging or ultrasound because ionizing radiations are more harmful to unborn babies than magnetic radiations and ultrasonic waves.

2. Exposure to radiations: CT scan imaging involves brief exposure to ionising radiations. In a CT scan, detailed information about a target tissue is obtained from different angles. Therefore, CT involves a comparatively high dose of ionising radiation than normal X- rays. Since your body is exposed to a high dose of ionising radiation, frequent CT scans may lead to cancer. 

Experts in this field chose a minimal radiation dose to get information about the target tissue. 

You can discuss possible risk factors of a CT scan with your doctor. 

3. Reactions to contrast material: In certain cases, your doctor may recommend that you receive a special dye called contrast material. Contrast material is a special dye. Certain patients are asked to drink it before the CT scan, and it can be inserted into the rectum before the procedure or injected into veins according to the part examined. 

Prepare yourself before you go for a CT scan

Patients are asked to do the following things:

1. To remove metal objects
2. Stop eating/drinking 
3. Remove personal clothing

Cancer risk of CT scan in COVID-19

Are CT scans helpful for diagnosing COVID-19?

Yes, CT scan is quite helpful in diagnosing COVID-19. This test is a rapid test (hardly takes 40 minutes to get a complete scan) for COVID-19 pneumonia suspected patients. When we compare the effectiveness and reliability of both the tests (CT scan and RT-PCR), CT scan proved to be a highly reliable and rapid screening tool. For this purpose high resolution, computed tomography is employed. The chest HRCT scan images have a comparatively high potential for the prediction of clinical outcomes of SARS- COV 2 patients. Hence, CT scan has proved to be an essential diagnostic tool for the management of COVID -19 affected individuals. The most basic concerns of these researchers include, 

1. In RT PCR, the sample size is quite small, consequently, the chances for false positive results will increase eventually.
2. Lack of information regarding the scoring system set to quantify the extent of lung involvement during the infection.
3. RT PCR can provide results of 100s to 1000s of samples at the same time, though this is quite helpful while testing masses but when it comes to the individual examination, cross-examination is always required as there can be chances of errors like sample exchange. Whereas, in the case of CT scan a patient is examined individually. Hence, there are no chances of mixing reports.

How does COVID-19 affect the lungs?

In simple terms, COVID-19 infection causes damage to the lining of the lungs, more precisely the walls of the alveoli (air sacs) of the lungs get adversely affected. This infection lead to breathing problems initially, and when the infection progress further, it infects the blood vessels, resulting in lung failure, which is termed as acute respiratory distress syndrome.

What are some severe consequences of the coronavirus disease?

The most severe symptoms of post COVID era include,

1. Shortness of breath
2. Cough
3. loss of speech 
4. Loss of mobility
5. confusion
6. Chest pain
7. heart palpitations – fast heartbeat or pounding
8. Brain fog- concentration issues and thinking problem
9. Sleep problems
10. Headache
11. Lightheadedness- dizziness 
12. Twitching or needles poking 
13. Change in smell or taste
14. Depression 
15. Anxiety that persist
16. Diarrhea
17. Stomach pain

How long does the virus that causes COVID-19 last on surfaces?

According to a recent report by WHO, there are variable results of surface survival time of coronavirus, however, it ranges from 2 hrs to 9 days. The survival time depends on various factors, which include, 

1. Surface type
2. Temperature
3. Viral strain
4. Relative humidity

What is the rapid diagnostic test for COVID-19?

Rapid diagnostic test more precisely, SARS-CoV-2 antigen rapid diagnostic tests are based on instant identification of viral antigens in nasal swab samples. The basic principle behind the test is the immune-viral interaction.

You May Also Like