CT Thorax scan has over 90% Covid test accuracy

Bengaluru: With an increase in the spread of Covid-19 there has been a surge in the percentage of false negative reports in the RT-PCR test among symptomatic patients. To check this, the State government has issued a circular that such cases should be identified and subject to CT Thorax scan. The circular states that CT Thorax has greater sensitivity and lower false negative than RT-PCR.

Dr. Sunil Kumar K, Consultant - Interventional Pulmonology, Aster CMI Hospital explained, "Anybody who has fever, cough, or any other Covid-19 symptoms will test positive only after a period of five days to one week through antigen test. The sensitivity of this test ranges between 50%-60%, which many at times raise the possibility of missing positive cases, which are also known as a 'false negative' result. Therefore, if someone has gone for a test earlier they may test negative. The second test which is currently available and is considered a 'gold standard' for Covid-19 testing is RT-PCR which has a sensitivity of 60-70%. This test depends on the prevalence of Covid infection in a person. If the prevalence is high, then the person will definitely test positive and chances are that their RT-PCR will show a sensitivity of 80%."

"However, there are chances that the remaining 20% of patients may walk out freely with a 'negative' report in hand as the prevalence of their virus may not be much in their bodies. Hence, the CT Thorax scan is recommended which can provide a test report with a diagnostic value of more than 90-95% accuracy. Even though it does not provide a 100% positive report but it can help the clinicians in understanding the pattern of the diseases based on the CT Thorax scan report," Kumar explained.

He suggested that if anybody who has symptoms and has undergone an RT-PCR test but tested negative are advised to also go for a CT Thorax scan.

"If the CT scan still shows that they are positive, then such patients should ideally repeat their RT-PCR test after 3-4 days. We recently came across a couple of patients who had tested negative based on the RT-PCR report but were found to be positive when we conducted their CT Scan and were monitored in COVID suspected wards" Kumar said.