A section of doctors in Tiruchy city of Tamil Nadu have claimed that more number of COVID-19 cases can be detected with a CT scan of the chest than by RT-PCR tests. Dr Mohamed Hakkim, who is an emergency physician explained this rationale that COVID-19 is a respiratory infection and it affects the lungs. CT-scan imaging of lungs can provide a good outcome and RT-PCR test can only detect if the virus is in the nose or throat. The extent of damage can be clearly seen in CT-scan when the virus infects the lungs.

According to sources, there have been instances where the PCR tests have come negative but patients were confirmed COVID-19 positive by CT scan. A senior doctor in MGMGH said that 70 cases were identified through RT-PCR and 100 cases were detected through HRCT. Dr K Govindaraj, Director of Dr G Vishwanathan Specialty Hospitals also said that CT scan is very sensitive and they have seen several cases of CT positive but PCR negative. RT-PCR is able to detect infection from 1 to 8 days. From the 4th day of the infection to 2 weeks, a CT scan is more sensitive and the patient is symptomatic.

One more reason cited is mutation of the coronavirus. Doctors have said that CT scan gives results in almost 15 minutes, whereas at least 24 hours is taken for PCR results. Radiologists had claimed that PCR had 70 to 80 percent efficiency. CT scan can generally detect COVID after day 5 of contracting infection.

Dr Bavaharan, Founder of Magnum Imaging and diagnostics said that there could be errors because of sampling time. Radiologists do follow an index called CO-RADS to check the severity of infection.

Dr Hakkim also said that the level of infection is mostly graded from very low or CO-RADS 1 to CO-RADS 6. CO-RADS 4 is doubtful for COVID and CO-RADS 5 and 6 are distinctive of COVID-19.

Private Doctors have also said that there are chances of PCR results to be negative and many infected cases might go undetected. According to the ICMR guidelines, only RT-PCR positive cases are reported as COVID. They have seen double the number of patients tested positive through CT-scan but have not been reported.

Source: The New Indian Express