How reliable are tests for COVID-19?

How reliable are tests for COVID-19?

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How reliable are test results for COVID-19?

One of the most commonly used tests to detect the new SARS-CoV-2 coronavirus does not appear to be as reliable as previously thought. The probability of a false negative result in the case of an existing disease is greater than one in five.

Researchers at the Johns Hopkins Bloomberg School of Public Health and the Johns Hopkins School of Medicine have now investigated how reliable the results of a widespread test for the identification of virus particles from SARS-CoV-2 are. They found that the test can show false negative results, even though the person being examined is actually infected with SARS-CoV-2. The results of the study were published in the English-language journal "Annals of Internal Medicine".

Seven published studies were analyzed

For the current investigation, seven previously published studies on the performance of the so-called reverse transcriptase polymerase chain reaction test were analyzed. The frogers determined that negative test results should be interpreted with particular caution. This is especially true for people who have likely been exposed to the virus or who have symptoms consistent with COVID-19.

What is the reverse transcriptase polymerase chain reaction test?

One of the most commonly used diagnostic tools, especially during the COVID-19 pandemic, is the reverse transcriptase polymerase chain reaction test. This test uses an airway sample to detect virus particles and determine if the subject may have been exposed to a virus.

Test is used all over the world

The above test has been used in laboratories around the world to determine if a person is infected with the SARS-CoV-2 virus that causes COVID-19. Although the test plays a vital role in fighting the spread of the virus, there are still some doubts about its reliability.

Probability of wrong result greater than 1 in 5

According to the researchers, the probability of a false negative test result, in which a person was infected, but the test shows a negative result, is greater than one in five and sometimes even much higher.

What influence does the time of the test have?

In other words, the test does not always seem to provide accurate results, and the timing of the test in particular does not appear to have a significant impact on the accuracy of the results, the researchers report in a press release.

Different test results on different days of infection

The study found that the probability of a false negative result decreased from 100 percent on the first day of infection to 67 percent on the fourth day. The so-called false negative rate dropped to 20 percent on the eighth day (three days after symptoms began to appear), the team reports.

Incorrect results increased on day 21

The researchers also found that the day a person started to develop actual symptoms of illness, the average false negative rate was 38 percent. In addition, the false negative rate began to increase again, from 21 percent on day nine to 66 percent on day 21. (as)

Author and source information

This text corresponds to the requirements of the medical literature, medical guidelines and current studies and has been checked by medical doctors.


  • Lauren M. Kucirka, Stephen A. Lauer, Oliver Laeyendecker, Denali Boon, Justin Lessler: Variation in False-Negative Rate of Reverse Transcriptase Polymerase Chain Reaction – Based SARS-CoV-2 Tests by Time Since Exposure, in Annals of Internal Medicine ( Published May 13, 2020), Annals of Internal Medicine
  • COVID-19 Story Tip: Beware of False Negatives in Diagnostic Testing of COVID-19, Johns Hopkins School of Medicine (Published May 26, 2020), Johns Hopkins School of Medicine

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