“Although RT-PCR test is the gold standard, right from the beginning of the pandemic it has had a 20% false negative rate and relying on clinical symptoms along with the tests has been followed for a while now,” said Dr M Raja Rao, superintendent, Gandhi Hospital.
In a study conducted at AIG hospitals, comparing RT-PCR positivity from nasopharyngeal (NP) and oropharyngeal (OP) nasal swabs and saliva, doctors found that in hospitalised patients RT-PCR by NP/OP swabs showed 80% positivity. In patients who tested negative by NP/OP swab, if saliva was tested, the per cent positivity increases to 95%.
“Emergence of viral variants that are no longer detectable by certain diagnostic tests is a real possibility due to the fact that the virus is constantly mutating. A negative RT-PCR result does not rule out SARS-CoV-2 infection. Consider negative RT-PCR result in combination with clinical observations, patient history, lab and radiological investigations and epidemiological information,” said Dr Nageshwar Reddy, chairman, AIG hospitals, after releasing a Covid-19 protocol guideline.
Other experts say that of the four main variants of concern, beta and gamma can be sometimes missed. “However, cases can also be missed due to timing of tests, vaccination status of the individual as vaccinated individuals clears the load of the virus much faster compared to others, there is a high possibility of missing out the infection,” said Dr Kiran Madhala, healthcare expert.