E-Paper
Antigen kits help Ghaziabad to increase virus testing by five times
A month after Ghaziabad began deploying antigen testing kits, the district has increased testing by almost five times and reduced the positivity rate.
A month after Ghaziabad began deploying antigen testing kits, the district has increased testing by almost five times and reduced the positivity rate.
Starting June 26, the district began using the kits at hot spots and containment zones and in time took it to other areas of the city, targeting high risk groups. Of all testing methods, 57.5% of samples were tested for antigens till July 28.
According to the health department data till July 28, the district took 94208 samples for testing, out of which 92716 tested and reported --- 53,320 (57.5) were under antigen testing, 37,662 (40.6%) reverse transcription-polymerase chain reaction (RT-PCR) tests and 1734 (1.9%) TrueNat tests.
Prior to deploying antigen testing kits, the district relied only on RT-PCR tests. At the time, its positivity rate was about 6.94% out of the 16,810 samples tested. On July 28, this number read 5.07%.
Antigen tests are inherently unreliable with very poor sensitivity, which means its ability to detect true positives is low and could result in many negative tests turning positive under an RT-PCR test. The Indian Council of Medical Research (ICMR) requires those testing negative and showing symptoms later to go for an RT-PCR test for confirmation.
Despite this, its share is high because of two advantages: point of care testing and no need of taking it to a laboratory, and that it gives a result within 30 minutes, as compared to the two days it would take an RT-PCR test.
“With more rapid kits now available we are testing more through it to find positive patients. Now, we have received a target of conducting 2000 rapid antigen tests and about 350 though RT-PCR per day,” said an officer from the health department who wished not to be named.
According to the official records, positivity through the rapid kits is about 1.41% with 53320 tests resulting in 1316 positive cases till July 28. On the other hand, the positivity through RT-PCR is about 3.65% with 3392 positive cases resulting out of 39396 RT-PCR tests conducted since March.
The experts said that positivity difference between the two tests is acceptable considering the advantages that antigen testing gives.
“The RT-PCR is time consuming and we require trained staff. The antigen test’s positive result is true positive,” said Dr Ashutosh Rawat, microbiologist from Columbia Asia Hospital, Ghaziabad. “Sample collection techniques also affect the results. If the sample is not picked up properly it may turn negative in both the type of tests. Further, the asymptomatic patients who do not turn positive with rapid kits are not at risk. So we have to accept the rapid test with genuine difference in comparison to RT-PCR test. My opinion is that a difference of 1% to 1.5% between the two type of tests then results are acceptable.”
In Ghaziabad, of the total samples tested using antigen tests, 18,293 tested negative and 16,279 were tested again under RT-PCR method, out of which 920 returned positive -- a positivity rate of 5.65%.
The district administration officials on the other hand said that they have planned to conduct about 3000-3500 tests per day.
“This will be achieved with majority of testing through rapid kits now available with us. The idea is to trace more positive patients and filter them out from the local population. So, this will help us in early detection and in faster treatment of such patients. The RT-PCR testing will also go on. Our RT-PCR testing will also get boost once our new laboratory (at MMG Hospital) which is already sanctioned by the government comes up,” said Ajay Shankar Pandey, district magistrate.
