NOT SO EASY HUNT
1 A swab is used to take a sample of the virus from the back of the nose or throat where the virus usually gathers.The swab should go in deep enough to get adequate amount of virus. 2 The swab is put in a vial containing a buffer solution which preserves the virus till the time the sample is processed
on April 20, researchers from the Oxford University, analysed nine COVID-19 rapid tests used in UK. Their specificity was good, between 85 and 100 per cent, but sensitivity was low, between 55 and 85 per cent. Due to low sensitivity, a positive result would indicate that the person was infected and has antibodies against the virus. But in case of a negative result, it is difficult to rule out if the person is infected. Thus, the researchers say, these tests are good for population-level surveys, but inadequate for patient applications.
The unreliability of antibody tests have been long known. In the case of influenza, its sensitivity is as low as 70 to 75 per cent, and thus false negative results are a major concern. Tests for dengue have variable performance, depending on the developer, serotype, medical history and duration of sickness. Even pregnancy kits that have been in use since 1976 and are generally considered reliable, have not been validated for reliability.
So when the World Health Organization (WHO) asked countries to “test, test, test”, it talked only about RT-PCR. But a dipstick analysis shows that there is little correlation between widespread use of these tests, disease prevalence and prevention of deaths (see 'Fighting blindfolded?').
selected from each continent two countries conducting maximum number of tests and compared their test rates with their rates of cases and deaths. Let's consider UK, Australia, New Zealand and US whose testing rates are almost same—they are conducting 50,000 to 60,000 tests per million population. As on May 30, fatality rates in Australia and New Zealand were just seven and eight per million, whereas the figures were a massive 944 for the UK and 622 for the US. While the Oceania countries have managed to keep their rates of infection at around 500, it has crossed 10,000 in US and reached 6,707 in UK.
This shows there are other factors that play a critical role in winning the battle than just widespread testing.