With widespread use of rapid antigen tests in Kashmir for the detection of Covid-19 cases, Doctors Association Kashmir (DAK) on Wednesday said these diagnostic tests miss a large number of positive cases obscuring the true picture of the outbreak in the valley.
“One in two persons infected with the novel coronavirus receive false negative results by rapid antigen test,” said DAK President and influenza expert Dr Nisar ul Hassan in a s statement issue here.
“At SMHS hospital, more than half of the patients who tested negative for Covid-19 in an antigen test later came positive with real time PCR method,” he said.
DAK President said while rapid tests provide results in minutes, they are far less accurate than the gold standard RT-PCR.
“Recent reports from Mumbai revealed that 60 percent of patients who tested negative in antigen tests at Nair hospital, came out positive when retested under RT-PCR,” he said.
“In a study, rapid antigen test detected between 11.1 percent and 45.7 percent of RT-PCR positive samples from Covid-19 patients,” he added.
Dr Nisar said antigen test has a sensitivity of around 50 percent – that means more than 50 percent of positive cases can be missed by the test.
“Not only do these rapid tests hinder the diagnosis in individual patients, but they also obscure the true extend of the outbreak,” he said.
“We may feel the cases are falling and we have begun to flatten the curve, but the reduction in the positive cases can simply be due to unreliable testing,” Dr Nisar said.
“The use of rapid tests could also mean letting many infected people return freely to the community spreading the virus to even more people.”
“Accurate diagnosis of Covid-19 infection is crucial to help identify and control infection. Low accuracy of rapid antigen test could diminish its usefulness as a screening tool,” he said.