PCR tests give fewer false-negative results in the morning, study claims

An hour before taking a smear for a PCR test, it is recommended not to eat, drink, smoke, brush your teeth, or even rinse your mouth in the morning or take antiseptic pills. All of these measures reduce the risk of receiving a false negative result.

However, American scientists have found that this risk is reduced in the case of taking the test in the morning.

According to Medportal.ru, during the study, specialists analyzed the results of more than 30,000 PCR tests. They compared the results obtained with the time of taking a smear, and also took into account data on sick patients in whom the test had not previously confirmed SARS-Cov-2.

The results showed a twofold change in the proportions of positive results during the day, with their maximum number falling at 14:00. According to scientists, this may also be because different groups of patients are tested at a certain time, but the most likely explanation lies in circadian fluctuations in immunity, which interacts with the pathogen in different ways during the day.

The authors of the study suggest that the discharge of SARS-Cov-2 is cyclical, with a peak at the beginning of the day. This observation coincides with the results of studies of other viruses, such as influenza, herpes and Dengue, when the interaction of the pathogen with the immune system leads to daily fluctuations in viral shedding. According to scientists, these findings may become the basis for adjusting the current recommendations for testing patients.

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