Why some COVID positive patients may test negative in the beginning

Underlining the importance of retesting for the correct diagnosis and timely treatment of COVID-19, the government of India has asked the states to retest all who are showing the symptoms of coronavirus but have tested negative. It should be noted that health experts have warned time and again about starting the treatment of those exhibiting clinical symtomps of COVID-19 while waiting for the confirmatory test results to arrive.

As India registers a skyrocketing single-day spike of 95,000 new cases of coronavirus infection on Wednesday, it becomes all the more important to pay attention to the people who are symptomatic but have tested negative for coronavirus. There have been several instances where patients were confirmed to be COVID positive only after multiple testing. These initial false negatives are not only dangerous for the patient, but they also run the risk of increasing community transmission.

Currently, there are three diagnostic tests to confirm the presence of novel coronavirus, which are the swab test (RT-PCR), antigen test and the antibody test. Out of these three, the RT-PCR test (reverse-transcription PCR) is considered to be the most sensitive one and looks for the presence of active infection in the body. While rapid antigen test has a high chance of false negatives, if a person tests positive through the antigen test, a confirmatory RT-PCR test is not required to confirm the presence of viral particles. The antibody test, on the other hand, only looks for antibodies to the SARS-CoV-2 virus and can only tell about a past infection.

The RT-PCR test works by identifying the RNA traces of the coronavirus through a swab sample taken from a person’s nose or throat. However, false negatives can occur at about 30 per cent of the time, as there are a lot of stages during the collection of the sample, where contamination may lead to errors. Hence, even though it is one of the most sensitive tests for coronavirus testing, the RT-PCR (reverse-transcription PCR) has a sensitivity of about 70 per cent currently.

A false negative simply means that a person infected with COVID-19 has been missed by the test. If the swab sample is not taken correctly to conduct RT-PCR, it may lead to a false negative. Also, there could be a low viral load present in the throat when compared to the nasopharynx.

Hence, an incorrectly taken swab can miss the viral particles altogether, or even if the viral load is too less in the samples, the chances of false negative increases.

Doctors and medical experts across the globe are of the notion that if a patient has developed clinical symtomps of the COVID-19 but repeatedly tests negative for the same, his treatment along the lines of COVID-19 should start. If the RT-PCR continues to be negative, chest CT scan or X-RAY should be done of the symptomatic person for further evaluation. Any manifestations (breathlessness, sore throat, fever etc,) which are consistent with COVID-19 should be provided with the same line of treatment for COVID-19 to prevent the disease from getting severe.

Hence, if you or someone you know have developed tell-tale symtomps of coronavirus but continues to test negative, it is important to consider yourself infected and take the necessary precautions.