Many government doctors on COVID-19 duty are coming across a significant number of patients who are symptomatic but tested negative. In such patients, the CT chest findings are suggestive of COVID-19; hence, they are treated as COVID-19 patients but are not included in the official figures, doctors say.
Inquiries with government doctors in many parts of the State, including Chennai, Tiruchi and Madurai, showed that a significant percentage of patients fall in this category: swab negative, typical COVID-19 findings in CT scan and clinical features.
A cross-section of doctors said that at a number of government hospitals, at least 30%-40% of patients were in this category and were treated in wards for persons with suspected COVID-19 symptoms. They said various factors were at play, including the lifting of swabs, the specificity of RT-PCR test and viral load.
“We are actually seeing a lot of such patients. In 30%-40% of patients, the swabs return negative, but the clinical features and CT findings are suggestive of COVID-19,” said a doctor at Government Omandurar Medical College Hospital.
At Rajiv Gandhi Government General Hospital (RGGGH), a doctor said 30% patients were COVID-19 negative but had CT findings. “These patients had the clinical features of COVID-19. This segment of patients need to be analysed,” he said.
Another doctor added, “Nowadays, we are seeing more symptomatic patients but they tested negative for COVID-19. The wards are full too.” A ward for persons with suspected COVID-19 symptoms was recently established at RGGGH.
Several such patients are admitted to Government Kilpauk Medical College Hospital too. “Any test will have specificity. False negatives are common. It is not possible to have a one test-based diagnosis. So, to corroborate, we look at the symptoms, do a CT/X-ray and a COVID panel for patients and treat them as COVID-19 patients,” a senior doctor said.
A few senior government doctors said there was a possibility of 25% false negative and false positive with RT-PCR testing. “It is left to the discretion of the treating physician when it comes to CT findings,” one of them noted.
“Around 2%-3% of patients test negative for COVID-19 but have clear CT findings. RT-PCR tests have 85% sensitivity and false negatives are common. When we have patients with CT findings, we treat them as COVID-19 positive. However, they will come under the category of persons with suspected symptoms of COVID-19. As per ICMR guidelines, only those whose swab returns positive for COVID-19 are to be counted,” a senior hospital authority said.