TABLE 3.

Possible reasons for false negative and positive results in nucleic acid detection.

	Factors	References
Sample preparation
Sample collection	• Improper materials: the swap containing calcium alginate or a stick has inhibitors against PCR. • Source of sample: gastrointestinal symptoms are related to prolonged virus RNA in gastrointestinal when upper respiratory symptoms disappeared with undetected virus RNA in respiratory tract. • Time of sample: the longer the interval between symptoms and detection is, the higher the probability of false negative is.	Premraj et al., 2020; Natarajan et al., 2022
Sample store	• Improper store and transport sample: RNA might degrade due to inappropriate temperature.
Detection technology
Target gene	• Deletion of gene fragments and genome variation on target gene would affect the use of existing primers.	Su et al., 2020
Limiting of detection	• Reaction settings, amplification efficiency, reverse transcription efficiency, etc., could influence the range of limiting of detection.	Yang S. et al., 2021
Patients
Drugs/Inhibitors	• heme and humic acid are common PCR inhibitors; drugs like Acyclovir also have been reported to inhibit Taq DNA polymerase	Yedidag et al., 1996
Infection dynamics and severity	• Infection severity and upper respiratory viral load of individual differences might contribute to false-negative results