RT-PCR Test v/s CT Scan – Which Is A Better Choice?

Introduction

As the surge in COVID-19 cases in India continues, the general public must educate themselves about the prescribed tests, scans and biomarker findings. Considering the raging COVID-19 pandemic, doctors aim to treat mild to moderate cases without the need to hospitalize the patient.

Mild COVID-19 symptoms can be fever, dry cough, headache, loss of taste and smell with oxygen levels in COVID patients more than 95%. As the oxygen level falls, they are more likely to become be hospitalised. Before that, let us know more about COVID testing in India. The most reliable and researched test is the RT-PCR COVID test to diagnose whether the patient is positive or negative for coronavirus.

Intended use of RT-PCR In COVID-19

Real-time reverse Transcription-Polymerase Chain reaction (RT-PCR) is a qualitative test to detect the presence of coronavirus in a person’s respiratory tract. The test involves collecting nasopharyngeal (nose) or oropharyngeal (throat) swabs from COVID-19 suspected people. RT-PCR is an advanced tool to amplify a selected nucleic acid fragment (sample) and detect SARS-CoV-2 RNA, the coronavirus.

One can get access to this test via in-home or in-lab services. While laboratory testing requires a visit, COVID testing at home is an easy method that eliminates the transportation hassle. A testing certified person will come from a registered laboratory to collect your sample and take it back to the lab for testing. It takes a maximum of 48 hours to deliver results and one can access their COVID-19 report online. It is available at both government and private hospitals or laboratories, where the cost varies from INR 700-1800, subjective to the state and the private lab.

The CT value in RT-PCR is different from the CT scan. What is the meaning of CT value in RT-PCR? CT indicates the cycle threshold. It is the number of cycles the process completed to detect the virus in the sample. As a result, a low CT value (17-24) indicates a high viral load and a high CT (more than 25) indicates a low viral load. 

RTPCR helps in detection of COVID virus in body and is Gold standard for diagnosis of COVID, CT only helps in assessing the extent of lung damage by COVID and does not detect COVID.

Dr. M.G. Kartheeka, MBBS, MD(Pediatrics)

CT Scan And When To Go For It

CT scan for COVID-19 is being misused for mild detection purposes. The harmful rays of CT match to about 200-300 X-rays. Renowned doctors have urged the public not to go for unnecessary CT scans for a mild COVID infection. 

Let us understand CT scan as a vital diagnostic tool for critical COVID cases currently. CT scan is an abbreviation for Computed Tomography Scan. A CT scan is simply a detailed version of an X-ray. It is capable of better understanding blood vessels and soft tissues. The COVID CT scan is a chest scan to check the conditions of your lungs and other parts of the respiratory tract. Can CT a scan help detect COVID? The most common finding in patients with severe COVID-19 is the ground glass pattern in their chest CT scan. This pattern is easy to identify through the following features:

• Multifocal lesions: Lesions (abnormality) present in several regions. In the initial stages of the disease, the inferior lobe of the lung contains one lesion (unifocal).
• These lesions are bilateral, present on both sides and peripheral.

Who should go for a CT scan during COVID and why?

Only those patients whose doctors have prescribed it or when oxygen saturation is below 90-92% or experience breathing difficulty should go for a CT scan for a COVID-19 severity check. Chest CT scans can help detect the severity or improvement of infection. One can access their CT scan report for COVID online within a few hours only for INR 2000-5000 subjective to the private lab.

RT PCR being a molecular test is more sensitive and accurate at detecting viral infections such as COVID-19 and Ebola. A combination of CT scan and RT PCR is more accurate than either of these tests alone for covid.

Dr. Ashish Bajaj, M.B.B.S., M.D. in Clinical Pharmacology and Toxicology

RT-PCR test v/s CT scan – Which Is A Better Choice?

CT scan is not an advised test by doctors to ‘detect’ COVID-19 in the mild infection stage. Both of the tests are important in their field of action. One requires RT-PCR to detect COVID-19 and CT scan to detect if progressive pneumonia is present. A CT scan is useful when the infection has spread to the lungs and detection by nose or oral swabs is not possible. A CT scan is advised when a person’s oxygen level goes below 92% or indicates serious COVID-19 symptoms.

RT-PCR tests are a safer choice than CT scanning. It saves the person from additional radiation and can be done in the comfort of their home. It reduces the interaction and exposure with other suspected COVID cases. But this test is incapable of detecting the infection if it has reached the lungs and is causing further complications.

Most important of all, consult your physician about your coronavirus symptoms. Ensure to get tested and follow-up for any tests they prescribe/recommend based on your condition.

Conclusion

So which one of these two wins? Both RT-PCR and CT scan have their pros and cons. If you witness any unusual symptoms like dry cough, mild fever and a slight headache, best consult your doctor and get yourself tested by RT-PCR. Learn the basics of your COVID report:

• Result: POSITIVE – It indicates the presence of RNA specific to SARS-CoV 2 in your sample. You are likely to spread the infection, so make isolation your first step.
• Result: NEGATIVE – It indicates the inadequacy of RNA specific to SARS-CoV 2 in your sample. A negative RT-PCR and a positive CT scan still suggest COVID-19. Keep a record of your COVID symptoms day by day and show them to your doctor.
• Result: INCONCLUSIVE – It indicates that the sample was not good enough to be tested or the viral load was too low. 

Doctors now do not wait for the results to arrive due to the testing load on labs. It is best to begin the treatment protocol from the first day of symptoms after consulting your doctor. The clinical value of chest CT can indicate the severity and progression of infection in the lungs. Due to its high sensitivity, the diagnostic tool will be used as a primary screening tool for critical COVID cases. COVID-19 cases in India today are nowhere near a safe range for those unaffected or not vaccinated. Research has shown that immunocompromised individuals are at a higher risk of contracting the infection. It is best to stay indoors and prevent infection.

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