The high sensitivity of PCR means it can detect small fragments of viral genome even after the patient has recovered – this leads to False positives. Further, it takes almost a week to get the test results back and within that time the infected people have already transmitted the disease.
COVID-19 Testing – Speed is more important than Sensitivity
Prof. Michael Mina, a Harvard Epidemiologist argues that during a pandemic “speed and frequency of testing are vastly more important than sensitivity.” He strongly advocates use of rapid and cheap at-home tests (like pregnancy tests) which will allow everyone to get tested every couple of days.
He goes on to suggest that “even if a rapid test is 1,000 times less sensitive than a PCR test” , there will be at max a delay of 8-24 hours before the rapid test will also turn positive. This is due to the exponential increase in viral particles after infection.
Several rapid antigen tests developed globally are yet to be utilized across the masses as they fail to reach the high sensitivity standards set by PCR. Prof Mina points out “all we’re doing with all of this testing (PCR) is clogging up the testing infrastructure.”