During the rapid diagnostic test for corona virus among some people in an urban area, 900 of them were found negative result and it was 3/4 of the number of tested people. Rest of the people were found to be suspected of COVID-19 and their throat swabs were tested. From the tested swabs, 3/20 were found infected
i) Find the tested number of people
ii) Find the number of suspected people.
iii) Find the number of infected people of COVID-19
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Answers
Answer:
Test results may come out negative even if one has contracted Covid-19, experts have warned, advising that those showing symptoms of the disease must be treated without waiting for a confirmatory test to prevent aggravation of the infection.
There have been several cases where patients showing clinical symptoms of Covid-19 have tested negative for the virus multiple times.They were confirmed positive after repeated tests, doctors said.
The general perception of the experts now is that a high degree of suspicion arising out of the clinical symptomatology and the CT scan reports should be the guiding factor for treatment rather than relying only on the RT-PCR test which has a sensitivity of only 70 per cent, Dr Neeraj Gupta, professor in the Department of Pulmonary, Critical Care and Sleep Medicine at the Safdarjung Hospital in Delhi, said.
Even the rapid antigen test has a sensitivity of only 40 per cent.
"So many patients will be missed if we rely only upon these tests," Dr Gupta said.
The antibody tests has a sensitivity of 90 per cent but they are only useful for confirming past exposure for SARS-CoV2 and have no value in the early stages of the disease.
"All the treatment strategies should be guided towards preventing the progress of the disease from its mild to moderate or moderate to severe and for that we cannot wait on test reports. We have to go by clinical symptoms," he explained.
Dr Vijay Gurjar, an assistant professor in the department of Geriatric Medicine at AIIMS here, said there have been several instances where the patients tested negative even after three or four RT-PCR tests despite clinical presentations and CT scans indicating atypical pneumonia which is highly suggestive of Covid-19.
Later on, they were found to have antibodies against coronavirus which means they had the infection but their results had not come out positive in the RT-PCR tests, he said
"Thus, if patients have the symptoms, more so, if he or she is an elderly or has co-morbidities, they should be treated on the lines of Covid-19 and managed accordingly without waiting for the test confirmation," Dr Gurjar said.
According to Dr Nikhil Modi, senior consultant of Respiratory, Critical care and Sleep Disorder at the Indraprastha Apollo Hospitals, New Delhi, one of the main reasons behind incorrect test results is the improper procedure of sample collection from the throat and the nose.
"If the sample is not collected in a proper manner, then it may lead to incorrect results. Also the viral load plays an important role, as when low, the test results may come out negative even if the patient has the infection," Dr Modi said.
"In cases where symptoms are highly suggestive of Covid-19 and the RT-PCR test continues to be negative even after repeated tests, a CT scan of the lungs can be useful in reaching a correct diagnosis," he elaborated.
The AIIMS' Resident Doctors' Association recently had written to the ICMR seeking formation of an expert committee for provision of professional enquiry for the unexpected, unexplained deaths during the pandemic.