Rapid antigen tests can show false negatives 50% of the time. On Aug 5 health department issued a circular to collect two sets of swabs while administering antigen tests – one nasal swab for antigen test and another set of nasal and throat swabs for a follow-up RTPCR test reports the Deccan Herald.
If the antigen test is negative, the swab collection center is required to send the set of samples collected for RTPCR testing to the testing lab mapped to the collection centre. If the antigen test is positive then the centre is required to discard the swabs.
As per the data since June 25 follow up of symptomatic antigen negatives in Belagavi has been 9%.
Belagavi Follow up rate- 9%
Follow up Positivity- 60% (Antigen negatives retested and turned positive)
Follow up rate: Ramanagara had 4%, Hassan 7%, Chitradurga had 8%, Dharwad 11%, Mandya 16%, Bengaluru Urban 21% and Kolar 22%. Not testing symptomatic antigen negatives who may test positive on RTPCR may lead to these people infecting others.
Incidentally, the follow-up positivity rate in each of these districts was quite high which means if not for a follow-up RTPCR test, these COVID patients would not have had a timely diagnosis, treatment and contact tracing.
In Vijayapura, it was 20%, Ramanagara 31%, Hassan 33%, Chitradurga 4%, Belagavi 60%, Dharwad 50%, Mandya 3%, Bengaluru Urban 26%, and Kolar 13%.