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Q. Can the COVID PCR test be false-positive if rapid antigen and PCR tests are negative after 48 hours?

Answered by
Dr. Basuki Nath Bhagat
and medically reviewed by Dr. Sushrutha Muralidharan
This is a premium question & answer published on Oct 18, 2021

Hi doctor,

I received a positive result from a COVID PCR test and then received a negative result from a rapid antigen and a PCR test two days later. I have had no symptoms. Can I reasonably assume that I am COVID-free? Kindly give your opinion.

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Hello,

Welcome to icliniq.com.

I read your query. Sorry for such mixed results.

First test COVID PCR (polymerase chain reaction) positive followed by negative result by rapid antigen testing (RAT) and COVID PCR after two days.

In your case, two different molecular testing platforms were used that is RAT, and COVID RT-PCR (reverse transcriptase-polymerase chain reaction), and both gave negative results on your sample after 48 hours. You mention no COVID symptoms are present. All these sums up possible false-positive results in your first sample.

COVID PCR testing is a highly specific and highly sensitive test to detect COVID-19; however, the false-positive result is possible with this test, and causes are like contamination during sampling, extraction, PCR amplification, cross-reactivity, etc.

In an asymptomatic individual without known close contact with an infectious individual, especially in a low prevalence setting, the finding of a positive RT-PCR test result should raise the possibility that the result is a false positive.

So, such individual should undergo further molecular testing (which you have done), and medical personnel or clinician should enquire about symptoms before labeling as negative.

I would suggest for you the same to visit your local doctor and get examined.

I hope this was helpful.


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