JOIN USRapid antigen tests — which were brought in to supplement RT-PCR testing due to rising Covid-19 cases — are providing anxious moments to health personnel as they have been unable to detect hundreds of symptomatic Covid-19 cases.
Authorities have tested 62,188 people so far in the state for Covid-19 using rapid antigen testing kits. Out of these, the test failed to identify 312 people even though they had tell-tale symptoms like fever, cough and breathlessness.
The data from the health department was confirmed by IAS officer Dr Shalini Rajneesh, who is overseeing antigen testing in the state, as being up to date from July 13.
According to the data, 312 people were eventually diagnosed as Covid-19-positive after vigilant health officials sent their samples along with 510 other symptomatics who had tested negative on the antigen method for additional verification using RT-PCR.
Out of the total 822 people, 37.9% (312 individuals) tested positive.
“While these 312 people represent an error rate of 0.5% in antigen testing, we must consider that they were tested a second time using RT-PCR only because they happened to be symptomatic,” said a virologist who did not want to be named.
“The question is what about the asymptomatics who test negative on the antigen?” he asked.
In several hard-hit rural districts such as Kalaburagi, Ramanagara and Bidar, the data shows that no people had been referred for additional RT-PCR testing at all.
Low testing in Bengaluru
Low testing rates also means we don’t know about the true error rate of the antigen tests, the expert said.
In Bengaluru, despite the Bruhat Bengaluru Mahanagara Palike (BBMP) stating it will conduct over 10,000 antigen tests per day in the city, data reveals that only 23,640 tests have been done in the city so far since July 13. This is about 1,818 tests per day or about 18.1% of their daily goal.
A government source explained that the daily target for testing is 11,500 in Bengaluru Urban and 500 in Bengaluru Rural. A BBMP doctor told DH that the 149 operational Urban Primary Health Clinics (UPHCs) have been given a daily target of 80 tests each.
“We have not reached that target,” the doctor said.
Among those subjected to antigen testing, however, 5,186 people tested positive and another 431 symptomatics who generated “false negative” reports were referred to the RT-PCR method for additional verification. Among these 32% (or 132 people) tested positive.
On Sunday, day two of a free mobile lab antigen testing programme by the BBMP, 384 antigen tests were done, out of which only 30 people tested positive.
A BBMP doctor clarified that antigen tests are only used only on people who are either likely positive or are primary or secondary contacts of known Covid-19 cases. Six extra people were referred for additional RT-PCR testing .
BBMP Commissioner N Manjunatha Prasad admitted that the testing was getting off to a slow start because staff was exhausted and also due to people not coming forward for testing.